Sample records for calculated harmonic vibrational

  1. Efficient procedure for the numerical calculation of harmonic vibrational frequencies based on internal coordinates

    SciTech Connect

    Miliordos, Evangelos; Xantheas, Sotiris S.

    2013-08-15

    We propose a general procedure for the numerical calculation of the harmonic vibrational frequencies that is based on internal coordinates and Wilson’s GF methodology via double differentiation of the energy. The internal coordinates are defined as the geometrical parameters of a Z-matrix structure, thus avoiding issues related to their redundancy. Linear arrangements of atoms are described with a dummy atom of infinite mass. The procedure has been automated in FORTRAN90 and its main advantage lies in the nontrivial reduction of the number of single point energy calculations needed for the construction of the Hessian matrix when compared to the corresponding number using double differentiation in Cartesian coordinates. For molecules of C1 symmetry the computational savings amount to 36! ? 30, where N is the number of atoms, with additional savings when symmetry is present. Typical applications for small and medium size molecules in their minimum and transition state geometries as well as hydrogen bonded clusters are presented. In all cases the frequencies based on internal coordinates differ on average by < 1 cm-1 from those obtained from Cartesian coordinates.

  2. Molecular structure, Normal Coordinate Analysis, harmonic vibrational frequencies, Natural Bond Orbital, TD-DFT calculations and biological activity analysis of antioxidant drug 7-hydroxycoumarin

    NASA Astrophysics Data System (ADS)

    Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.

    2013-01-01

    In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the ?* and ?* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis.

  3. Vibration analysis considering higher harmonics of electromagnetic forces for rotating electric machines

    Microsoft Academic Search

    Shigeru SAKAMOTO; Tosuke HIRATA; Takashi KOBAYASHI; Kenzo KAJIWARA

    1999-01-01

    A method is described to calculate vibration due to electromagnetic forces for rotating electric machines. This method can calculate the frequency response of vibration due to higher harmonics of electromagnetic forces. The usefulness of this method is verified through the agreement between calculated and measured results for a three-phase\\/four-pole induction motor. The authors also calculate the complicated dynamic behavior caused

  4. Stator current harmonics and their causal vibrations: a preliminary investigation of sensorless vibration monitoring applications

    Microsoft Academic Search

    Caryn M. Riley; Brian K. Lin; Thomas G. Habetler; Gerald B. Kliman

    1999-01-01

    This paper presents an initial study into the relationship between vibration and current harmonics of electric motors, including the effect of externally induced vibrations. This relationship was investigated experimentally on both new motors, on a vibration stand, and a motor with bearing wear. Both theory and experimental results show that a change in the RMS value of the stator current

  5. Vibrational-state and isotope dependence of high-order harmonic generation in water molecules

    SciTech Connect

    Falge, Mirjam; Engel, Volker [Universitaet Wuerzburg, Institut fuer Physikalische Chemie, Am Hubland, D-97074 Wuerzburg (Germany); Lein, Manfred [Centre for Quantum Engineering and Space-Time Research (QUEST) and Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)

    2010-02-15

    We report calculations on high-order harmonic generation in water molecules. Spectra are determined for various initial vibrational states of H{sub 2}O and its isotope D{sub 2}O. It is demonstrated that the ratio of the spectra for D{sub 2}O and H{sub 2}O is close to unity when the initial state is the vibronic ground state, indicating that nuclear dynamics is of minor importance. For vibrationally excited initial states, the high-harmonic intensities show a clear dependence on both the initial-state quantum number and the isotopic species.

  6. Modeling Stretching Modes of Common Organic Molecules with the Quantum Mechanical Harmonic Oscillator: An Undergraduate Vibrational Spectroscopy Laboratory Exercise

    ERIC Educational Resources Information Center

    Parnis, J. Mark; Thompson, Matthew G. K.

    2004-01-01

    An introductory undergraduate physical organic chemistry exercise that introduces the harmonic oscillator's use in vibrational spectroscopy is developed. The analysis and modeling exercise begins with the students calculating the stretching modes of common organic molecules with the help of the quantum mechanical harmonic oscillator (QMHO) model.

  7. Forced harmonic vibration of a Duffing oscillator with

    E-print Network

    is negative for positive damping ratio z; that is, local volumes in the y1; y2; tð Þ space are contracted5 Forced harmonic vibration of a Duffing oscillator with linear viscous damping Tamas Kalmar-Nagy1,4]. The nondimensional Duffing equation with damping and external forcing studied in this chapter has the form y þ 2z _y

  8. Higher Harmonic Forces in Purely Crossflow Vortex-Induced Vibrations

    NASA Astrophysics Data System (ADS)

    Modarres-Sadeghi, Yahya; Seyed-Aghazadeh, Banafsheh; Bourguet, Remi; Karniadakis, George; Triantafyllou, Michael

    2013-11-01

    In vortex-induced vibrations (VIV) of flexibly-mounted rigid cylinders free to oscillate both in the inline and crossflow directions, higher (3rd) harmonic forces have already been observed in the crossflow direction. In the present work, we report higher harmonic force components for a flexibly-mounted rigid cylinder with only one degree of freedom in the crossflow direction. We show that the inline displacement is not necessary to observe higher harmonic components in the crossflow force spectrum. Due to the relative velocity of the cylinder with respect to the oncoming flow, the lift and drag forces make an angle with respect to the crossflow and inline directions, and the contribution of the components of each of these forces in the crossflow direction results in a 3rd harmonic force component. These higher harmonic components have been observed in self-excited VIV experiments, performed in a water tunnel for a Reynolds number range of Re = 400-1000, as well as in numerical simulation results at Re = 100. We also find that the maximum ratio of the 3rd harmonic to the 1st harmonic occurs when the phase between the crossflow force and displacement changes from 0 to 180 degrees, resulting in a small first harmonic component.

  9. Vibrational Spectra of the MLCl{_2} Complex from Theoretical Calculations

    NASA Astrophysics Data System (ADS)

    Catikkas, Berna

    2012-06-01

    The geometric and vibrational parameters (harmonic and anharmonic frequencies) of the MLCl{_2} [M= Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg; L= Ethylenediamine (en)] donor-acceptor complexes have been studied by using HF and MPW1PW91+iop(3/76=00572004280)/gen methods. Binding, reorganization, atomization, HOMO-LUMO and ionization potential energies have also been calculated with the same method. SQM calculations have been performed by using anharmonic frequencies and experimental data. The obtained results were found to be in good agreement with the corresponding experimental findings.

  10. Vibrational Spectra and Quantum Calculations of Ethylbenzene

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Qiu, Xue-jun; Wang, Yan-mei; Zhang, Song; Zhang, Bing

    2012-10-01

    Normal vibrations of ethylbenzene in the first excited state have been studied using resonant two-photon ionization spectroscopy. The band origin of ethylbenzene of S1?S0 transition appeared at 37586 cm-1. A vibrational spectrum of 2000 cm-1 above the band origin in the first excited state has been obtained. Several chain torsions and normal vibrations are obtained in the spectrum. The energies of the first excited state are calculated by the time-dependent density function theory and configuration interaction singles (CIS) methods with various basis sets. The optimized structures and vibrational frequencies of the S0 and S1 states are calculated using Hartree-Fock and CIS methods with 6-311++G(2d,2p) basis set. The calculated geometric structures in the S0 and S1 states are gauche conformations that the symmetric plane of ethyl group is perpendicular to the ring plane. All the observed spectral bands have been successfully assigned with the help of our calculations.

  11. Vibrational spectra and DFT calculations of squalene

    NASA Astrophysics Data System (ADS)

    Chun, Hye Jin; Weiss, Taylor L.; Devarenne, Timothy P.; Laane, Jaan

    2013-01-01

    The isoprenoid compound squalene is a building block molecule for the production of essential cellular molecules such as membrane sterols, has several therapeutic activities including anticancer properties, and has commercial applications for a variety of industries including the production of cosmetics. While the physical structure of squalene has been known for many years, a spectroscopic understanding of the squalene molecular structure and how these spectrometric properties relate to the physical squalene structure has yet to be reported. In the present work we present the Raman and infrared spectra of liquid squalene, complemented by DFT calculations. The molecule has 234 vibrational frequencies and these have been categorized according to the different types of vibrational modes present. The vibrational modes are highly mixed and these have been assigned for the more prominent infrared and Raman bands.

  12. Balancing Vibrations at Harmonic Frequencies by Injecting Harmonic Balancing Signals into the Armature of a Linear Motor/Alternator Coupled to a Stirling Machine

    NASA Technical Reports Server (NTRS)

    Holliday, Ezekiel S. (Inventor)

    2014-01-01

    Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

  13. Piezoelectric MEMS energy harvesting systems driven by harmonic and random vibrations

    Microsoft Academic Search

    Lars-Cyril Blystad; Einar Halvorsen; Svein Husa

    2010-01-01

    Switching power conditioning techniques are known to greatly enhance the performance of linear piezoelectric energy harvesters subject to harmonic vibrations. With such circuits, little is known about the effect of mechanical stoppers that limit the motion or about waveforms other than harmonic vibrations. This work presents SPICE simulations of piezoelectric micro energy harvester systems that differ in choice of power

  14. Hyperpolarizabilities of the methanol molecule: A CCSD calculation including vibrational corrections.

    PubMed

    Dutra, Adriano S; Castro, Marcos A; Fonseca, Tertius L; Fileti, Eudes E; Canuto, Sylvio

    2010-01-21

    In this work we present the results for hyperpolarizabilities of the methanol molecule including vibrational corrections and electron correlation effects at the CCSD level. Comparisons to random phase approximation results previously reported show that the electron correlation is in general important for both electronic contribution and vibrational corrections. The role played by the anharmonicities on the calculations of the vibrational corrections has also been analyzed and the obtained results indicate that the anharmonic terms are important for the dc-Pockels and dc-Kerr effects. For the other nonlinear optical properties studied the double-harmonic approximation is found to be suitable. Comparison to available experimental result in gas phase for the dc-second harmonic generation second hyperpolarizability shows a very good agreement with the electronic contribution calculated here while our total value is 14% larger than the experimental value. PMID:20095739

  15. Dynamical properties of an harmonic oscillator impacting a vibrating wall.

    PubMed

    de Alcantara Bonfim, O F

    2009-05-01

    The dynamics of a spring-mass system under repeated impact with a vibrating wall is investigated using the static wall approximation. The evolution of the harmonic oscillator is described by two coupled difference equations. These equations are solved numerically, and in some cases exact analytical expressions have also been found. For a periodically vibrating wall, Fermi acceleration is only found at resonance. There, the average rebounding velocity increases linearly with the number of collisions. Near resonance, the average rebounding velocity grows initially with the number of collisions and eventually reaches a plateau. In the vicinity of resonance, the motion of the oscillator exhibits scaling properties over a range of frequency ratios. The presence of dissipation at resonance destroys the Fermi-acceleration process and induces scaling behavior similar to that at near resonance. For a moving wall with a random amplitude at collisions, Fermi acceleration is observed independently of the ratio between the wall and oscillator frequencies. In this case the average rebounding velocity grows with the square root of the number of collisions with the wall. Also, in this latter case, dissipation suppresses the Fermi-acceleration mechanism and induces a scaling behavior with the same universality class as that of the dissipative bouncing ball model with random external perturbations. PMID:19518541

  16. Definitions of non-stationary vibration power for time-frequency analysis and computational algorithms based upon harmonic wavelet transform

    NASA Astrophysics Data System (ADS)

    Heo, YongHwa; Kim, Kwang-joon

    2015-02-01

    While the vibration power for a set of harmonic force and velocity signals is well defined and known, it is not as popular yet for a set of stationary random force and velocity processes, although it can be found in some literatures. In this paper, the definition of the vibration power for a set of non-stationary random force and velocity signals will be derived for the purpose of a time-frequency analysis based on the definitions of the vibration power for the harmonic and stationary random signals. The non-stationary vibration power, defined as the short-time average of the product of the force and velocity over a given frequency range of interest, can be calculated by three methods: the Wigner-Ville distribution, the short-time Fourier transform, and the harmonic wavelet transform. The latter method is selected in this paper because band-pass filtering can be done without phase distortions, and the frequency ranges can be chosen very flexibly for the time-frequency analysis. Three algorithms for the time-frequency analysis of the non-stationary vibration power using the harmonic wavelet transform are discussed. The first is an algorithm for computation according to the full definition, while the others are approximate. Noting that the force and velocity decomposed into frequency ranges of interest by the harmonic wavelet transform are constructed with coefficients and basis functions, for the second algorithm, it is suggested to prepare a table of time integrals of the product of the basis functions in advance, which are independent of the signals under analysis. How to prepare and utilize the integral table are presented. The third algorithm is based on an evolutionary spectrum. Applications of the algorithms to the time-frequency analysis of the vibration power transmitted from an excitation source to a receiver structure in a simple mechanical system consisting of a cantilever beam and a reaction wheel are presented for illustration.

  17. Influence of vibrational states on high-order-harmonic generation and an isolated attosecond pulse from a N2 molecule

    NASA Astrophysics Data System (ADS)

    Guo, Jing; Ge, Xin-Lei; Zhong, Huiying; Zhao, Xi; Zhang, Meixia; Jiang, Yuanfei; Liu, Xue-Shen

    2014-11-01

    The high-order-harmonic generation (HHG) from the N2 molecule in an intense laser field is investigated by applying the Lewenstein method. The initial state is constructed as a linear combination of the highest occupied molecular orbital (HOMO) and the lower-lying orbital below the HOMO, which is well described by a Gaussian wave packet generated by using the gamess-uk package. The HHG with different vibrational states of N2 are calculated and our results show that the harmonic intensity can be enhanced by higher vibrational states, which can be explained by the ionization probability. We also compared the cases with a different full width at half maximum of laser fields together, which can be well understood by the time-frequency analysis and the three-step model. Finally, the attosecond pulse generation is studied with different vibrational states, where a series of attosecond pulses can be produced with the shortest being 91 as.

  18. Piezoelectric MEMS energy harvesting systems driven by harmonic and random vibrations.

    PubMed

    Blystad, Lars-Cyril; Halvorsen, Einar; Husa, Svein

    2010-04-01

    Switching power conditioning techniques are known to greatly enhance the performance of linear piezoelectric energy harvesters subject to harmonic vibrations. With such circuits, little is known about the effect of mechanical stoppers that limit the motion or about waveforms other than harmonic vibrations. This work presents SPICE simulations of piezoelectric micro energy harvester systems that differ in choice of power conditioning circuits and stopper models. We consider in detail both harmonic and random vibrations. The nonlinear switching conversion circuitry performs better than simple passive circuitry, especially when mechanical stoppers are in effect. Stopper loss is important under broadband vibrations. Stoppers limit the output power for sinusoidal excitations, but result in the same output power whether the stoppers are lossy or not. When the mechanical stoppers are hit by the proof mass during high-amplitude vibrations, nonlinear effects such as saturation and jumps are present. PMID:20378453

  19. Influence of harmonic components on electromagnetic vibration for a permanent magnet motor

    Microsoft Academic Search

    Tetsuya Hattori; Katsuyuki Narita; Takashi Yamada; Yoshiyuki Sakashita; Kan Akatsu

    2010-01-01

    In this paper, the influence of the harmonic components of the electromagnetic force caused by manufacturing error on the electromagnetic vibration was examined. The influence of the electromagnetic force generated by manufacturing errors causes the rotor eccentricity and distorts the stator creating an imbalance excitation force triggering electromagnetic vibration. Furthermore we verified that the magnetic imbalance largely effects the electromagnetic

  20. VIBRATION OF A BEAM INDUCED BY HARMONIC MOTION OF A HEAT SOURCE

    Microsoft Academic Search

    J. Kidawa-Kukla

    1997-01-01

    In this paper, a solution to the problem of thermally induced vibration of a uniform, simply supported beam is presented. The effect of internal damping on the vibration is considered. The temperature of the rectangular beam changes as a result of heating by a laser beam. The centre of the laser spot moves harmonically around a fixed point of the

  1. Effect of nuclear vibration on high-order-harmonic generation of aligned H2 + molecules

    NASA Astrophysics Data System (ADS)

    Telnov, Dmitry A.; Heslar, John; Chu, Shih-I.

    2014-12-01

    High-order-harmonic generation (HHG) spectra have been calculated for H2 + molecules aligned parallel to the polarization of the laser field. We make use of the Jacobi coordinates and neglect the rotation of the nuclei. The remaining time-dependent Schrödinger equation is three dimensional in spatial coordinates, one of them being the internuclear separation and the other two describing the electronic motion. The problem is solved using the accurate and efficient time-dependent generalized pseudospectral method in prolate spheroidal coordinates for the electronic coordinates and Fourier grid method for the internuclear separation. Laser pulses with a carrier wavelength of 800 nm, a duration of ten optical cycles, and a peak intensity of 2 ×1014 W/cm2 have been used in the calculations. Our HHG spectra, which incorporate the effect of nuclear vibration, generally exhibit a significant deviation from those calculated for the fixed internuclear separations. The low-energy regions of the spectra, however, resemble those for the nuclei fixed at larger separations, while the high-energy regions are closer to those for the nuclei fixed at smaller internuclear distances. The dynamics of the nuclear vibrational wave packet is also obtained and analyzed.

  2. Coupled rotor-flexible fuselage vibration reduction using open loop higher harmonic control

    NASA Technical Reports Server (NTRS)

    Papavassiliou, I.; Friedmann, P. P.; Venkatesan, C.

    1991-01-01

    A fundamental study of vibration prediction and vibration reduction in helicopters using active controls was performed. The nonlinear equations of motion for a coupled rotor/flexible fuselage system have been derived using computer algebra on a special purpose symbolic computer facility. The trim state and vibratory response of the helicopter are obtained in a single pass by applying the harmonic balance technique and simultaneously satisfying the trim and the vibratory response of the helicopter for all rotor and fuselage degrees of freedom. The influence of the fuselage flexibility on the vibratory response is studied. It is shown that the conventional single frequency higher harmonic control is capable of reducing either the hub loads or only the fuselage vibrations but not both simultaneously. It is demonstrated that for simultaneous reduction of hub shears and fuselae vibrations a new scheme called multiple higher harmonic control is required.

  3. Calculation of four-particle harmonic-oscillator transformation brackets

    NASA Astrophysics Data System (ADS)

    Germanas, D.; Kalinauskas, R. K.; Mickevi?ius, S.

    2010-02-01

    A procedure for precise calculation of the three- and four-particle harmonic-oscillator (HO) transformation brackets is presented. The analytical expressions of the four-particle HO transformation brackets are given. The computer code for the calculations of HO transformation brackets proves to be quick, efficient and produces results with small numerical uncertainties. Program summaryProgram title: HOTB Catalogue identifier: AEFQ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFQ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1247 No. of bytes in distributed program, including test data, etc.: 6659 Distribution format: tar.gz Programming language: FORTRAN 90 Computer: Any computer with FORTRAN 90 compiler Operating system: Windows, Linux, FreeBSD, True64 Unix RAM: 8 MB Classification: 17.17 Nature of problem: Calculation of the three-particle and four-particle harmonic-oscillator transformation brackets. Solution method: The method is based on compact expressions of the three-particle harmonics oscillator brackets, presented in [1] and expressions of the four-particle harmonics oscillator brackets, presented in this paper. Restrictions: The three- and four-particle harmonic-oscillator transformation brackets up to the e=28. Unusual features: Possibility of calculating the four-particle harmonic-oscillator transformation brackets. Running time: Less than one second for the single harmonic-oscillator transformation bracket. References:G.P. Kamuntavi?ius, R.K. Kalinauskas, B.R. Barret, S. Mickevi?ius, D. Germanas, Nuclear Physics A 695 (2001) 191.

  4. Full dimensional Franck-Condon factors for the acetylene [~ over A] [superscript 1]A[subscript u] — [~ over X] [superscript 1?[+ over g] transition. I. Method for calculating polyatomic linear—bent vibrational intensity factors and evaluation of calculated intensities for the gerade vibrational modes in acetylene

    E-print Network

    Park, Barratt

    Franck-Condon vibrational overlap integrals for the [~ over A] [superscript 1]A[subscript u] — [~ over X [superscript 1]?[+ over g] transition in acetylene have been calculated in full dimension in the harmonic normal mode ...

  5. Application of higher harmonic blade feathering on the OH-6A helicopter for vibration reduction

    NASA Technical Reports Server (NTRS)

    Straub, F. K.; Byrns, E. V., Jr.

    1986-01-01

    The design, implementation, and flight test results of higher harmonic blade feathering for vibration reduction on the OH-6A helicopter are described. The higher harmonic control (HHC) system superimposes fourth harmonic inputs upon the stationary swashplate. These inputs are transformed into 3P, 4P and 5P blade feathering angles. This results in modified blade loads and reduced fuselage vibrations. The primary elements of this adaptive vibration suppression system are: (1) acceleration transducers sensing the vibratory response of the fuselage; (2) a higher harmonic blade pitch actuator system; (3) a flightworthy microcomputer, incorporating the algorithm for reducing vibrations, and (4) a signal conditioning system, interfacing between the sensors, the microcomputer and the HHC actuators. The program consisted of three distinct phases. First, the HHC system was designed and implemented on the MDHC OH-6A helicopter. Then, the open loop, or manual controlled, flight tests were performed, and finally, the closed loop adaptive control system was tested. In 1983, one portion of the closed loop testing was performed, and in 1984, additional closed loop tests were conducted with improved software. With the HHC system engaged, the 4P pilot seat vibration levels were significantly lower than the baseline ON-6A levels. Moreover, the system did not adversely affect blade loads or helicopter performance. In conclusion, this successful proof of concept project demonstrated HHC to be a viable vibration suppression mechanism.

  6. HVDC-AC system interaction from AC harmonics. Volume 1. Harmonic impedance calculations. Final report

    SciTech Connect

    Breuer, G D; Chow, J H; Lindh, C B; Miller, N W; Numrich, F H; Price, W W; Turner, A E; Whitney, R R

    1982-09-01

    Improved methods are needed to characterize ac system harmonic behavior for ac filter design for HVDC systems. The purpose of this General Electric Company RP1138 research is to evaluate the present filter design practice and to investigate methods for calculating system harmonic impedances. An overview of ac filter design for HVDC systems and a survey of literature related to filter design have been performed. Two methods for calculating system harmonic impedances have been investigated. In the measurement method, an instrumentation system for measuring system voltage and current has been assembled. Different schemes of using the measurements to calculate system harmonic impedances have been studied. In the analytical method, a procedure to include various operating conditions has been proposed. Computer programs for both methods have been prepared, and the results of the measurement and analytical methods analyzed. A conclusion of the project is that the measurement and analytical methods both provided reasonable results. There are correlations between the measured and analytical results for most harmonics, although there are discrepancies between the assumptions used in the two methods. A sensitivity approach has been proposed to further correlate the results. From the results of the analysis, it is recommended that both methods should be tested further. For the measurement method, more testing should be done to cover different system operating conditions. In the analytical method, more detailed models for representing system components should be studied. In addition, alternative statistical and sensitivity approaches should be attempted.

  7. Harmonic motion detection in a vibrating scattering medium

    Microsoft Academic Search

    Matthew W. Urban; Shigao Chen; James F. Greenleaf

    2008-01-01

    Elasticity imaging is an emerging medical imaging modality that seeks to map the spatial distribution of tissue stiffness. Ultrasound radiation force excitation and motion tracking using pulse-echo ultrasound have been used in numerous methods. Dynamic radiation force is used in vibrometry to cause an object or tissue to vibrate, and the vibration amplitude and phase can be measured with exceptional

  8. Dynamic (hyper)polarizabilities of the ozone molecule: coupled cluster calculations including vibrational corrections.

    PubMed

    Naves, Emílio S; Castro, Marcos A; Fonseca, Tertius L

    2011-02-01

    In this work, we present results for dynamical (hyper)polarizabilities of the ozone molecule with inclusion of vibrational corrections. Electronic contributions for dynamic properties were computed analytically at the single and double coupled cluster level through response theories for the frequencies 0, 0.0239, 0.0428, and 0.0656 hartree. In the static limit, the electronic contributions were also computed at the single and double coupled cluster with perturbative correction of connected triple excitations level by means of the finite-field method. It was found that the inclusion of connected triple excitations is important, especially for a reliable description of the hyperpolarizabilities. Vibrational corrections were calculated by means of the perturbation theoretical method. The zero-point vibrational average correction was found to be relevant only for the linear polarizability, representing approximately 8% of the corresponding electronic contribution. Results also showed that the pure vibrational correction is relevant for the dc-Pockels effect, dc-second harmonic generation, intensity dependent refractive index, and dc-Kerr effect nonlinear optical processes. The double-harmonic approximation is in general suitable to compute this correction, the anharmonicity being small for the dc-Kerr effect and negligible for the other processes. PMID:21303128

  9. Molecular structure, vibrational spectra and DFT molecular orbital calculations (TD-DFT and NMR) of the antiproliferative drug Methotrexate

    NASA Astrophysics Data System (ADS)

    Ayyappan, S.; Sundaraganesan, N.; Aroulmoji, V.; Murano, E.; Sebastian, S.

    2010-09-01

    The FT-IR and FT-Raman spectral studies of the Methotrexate (MTX) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of MTX have been investigated with the help of B3LYP density functional theory (DFT) using 6-31G(d) as basis set. Detailed analysis of the vibrational spectra has been made with the aid of theoretically predicted vibrational frequencies. The vibrational analysis confirms the differently acting ring modes, steric repulsion, conjugation and back-donation. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complement with the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. Good correlations between the experimental 1H and 13C NMR chemical shifts in DMSO solution and calculated GIAO shielding tensors were found.

  10. Effect of nuclear vibration on high-order harmonic generation of aligned H2+ molecules

    NASA Astrophysics Data System (ADS)

    Telnov, Dmitry A.; Heslar, John; Chu, Shih-I.

    2014-05-01

    High-order harmonic generation (HHG) spectra have been calculated for H2+molecules aligned in the direction parallel to the polarization of the laser field. We make use of the Jacobi coordinates and neglect the rotation of the nuclei. The remaining time-dependent Schrödinger equation is 3D in spatial coordinates, one of them being the internuclear separation and the other two describing the electronic motion. The problem is solved using the accurate and efficient time-dependent generalized pseudospectral method in prolate spheroidal coordinates for the electronic coordinates and Fourier grid method for the internuclear separation. Laser pulses with the carrier wavelength of 800 nm, duration of 10 optical cycles, and several peak intensities have been used in the calculations. Our HHG spectra obtained fully beyond the Born-Oppenheimer approximation generally exhibit a significant deviation from those calculated for the fixed internuclear separations. The low-energy regions of the spectra, however, resemble those for the nuclei fixed at larger separations while the high-energy regions are closer to those for the nuclei fixed at smaller internuclear distances. The dynamics of the nuclear vibrational wave packet is also obtained and analyzed. This work is partially supported by DOE.

  11. Ground vibration due to a high-speed moving harmonic rectangular load on a

    E-print Network

    Avignon et des Pays de Vaucluse, Université de

    Ground vibration due to a high-speed moving harmonic rectangular load on a poroviscoelastic half by high-speed moving loads on poroviscoelastic half-space Corresponding author. Tel: +33 (0- monic rectangular load, is investigated theoretically. The problem is three-dimensional and the interior

  12. A theoretical study of the harmonic vibrational frequencies of SiO 4H 3X (X?H,Li and Na): model structures for silicate surfaces

    NASA Astrophysics Data System (ADS)

    Sosa, Carlos; Ferris, Kim F.; Noga, Josef

    1992-01-01

    The influence of alkali metals on the molecular spectra of silicates has been investigated using ab initio molecular orbital methods. The atomic polar tensors, harmonic vibrational frequencies and absolute infrared intensities were calculated on a series of model compounds (SiO 4H 3X;X? H, Li and Na). The geometries and harmonic vibrational frequencies were calculated at the Hartree-Fock level using 3-21G and 3-21G(d) (d functions on Si,Li and Na) basis sets. The SiO 4H 3X models show a bridging type structure between the alkali metals and neighbouring oxygen atom. The effects of correlation and anharmonicities were estimated by scaling the vibrational frequencies by a single parameter (0.89). Scaled harmonic vibrational frequencies for the OH stretches in SiO 4H 3X (X?Li and Na) are predicted lower in frequency in comparison to Si (OH) 4. Lowering in the intrinsic vibrational frequencies for the OH stretches suggests an increase in the acidity of the remaining OH groups.

  13. A vibrational spectroscopy study on 3-aminophenylacetic acid by DFT calculations.

    PubMed

    Akkaya, Yasemin; Balci, Kubilay; Goren, Yeliz; Akyuz, Sevim

    2015-08-01

    In this study, in which the group vibrations of 3-aminophenylacetic acid were investigated by electronic structure calculations based on Density Functional Theory (DFT), the possible stable conformers of the molecule were searched through a relaxed "potential energy surface scan" carried out at B3LYP/6-31G(d) level of theory. The corresponding equilibrium geometrical and vibrational spectral data for each of the determined stable conformers and for their possible dimer structures were obtained through "geometry optimisation" and "frequency" calculations carried out at B3LYP/6-31G(d) and B3LYP/6-311G++(d,p) levels of theory. The obtained results confirmed that anharmonic wavenumbers calculated at B3LYP/6-311G++(d,p) level generally quite well agree with the experimental wavenumbers, however, harmonic wavenumbers calculated at both levels of theory need an efficient refinement for a satisfactory agreement with experiment. In particular, the harmonic wavenumbers, IR and Raman intensities refined within Scaled Quantum Mechanical Force Field (SQM FF) methodology constituted the primary data set in the interpretation of the experimental FT-IR, FT-Raman and dispersive Raman spectra of 3-aminophenylacetic acid. By the help of these refined spectral data, the effects of conformation and intermolecular hydrogen bonding on the fundamental bands observed in the experimental spectra could be correctly predicted. PMID:25854610

  14. Calculation of vibrational zero-point energy

    Microsoft Academic Search

    M. Rahal; M. Hilali; A. El Hammadi; M. El Mouhtadi; A. El Hajbi

    2001-01-01

    We have established an empirical formula for calculating the zero-point energy (ZPE) of organic compounds. We applied this formula to 80 molecular systems, and compared it to the AM1 semi-empirical method, in both cases with satisfactory results. We also observed that the sum ZPE+H(T)?H(0) and the empirically derived ZPE(empirical) are related by a quasi-linear relation.

  15. Vibronic-structure tracking: A shortcut for vibrationally resolved UV/Vis-spectra calculations

    NASA Astrophysics Data System (ADS)

    Barton, Dennis; König, Carolin; Neugebauer, Johannes

    2014-10-01

    The vibrational coarse structure and the band shapes of electronic absorption spectra are often dominated by just a few molecular vibrations. By contrast, the simulation of the vibronic structure even in the simplest theoretical models usually requires the calculation of the entire set of normal modes of vibration. Here, we exploit the idea of the mode-tracking protocol [M. Reiher and J. Neugebauer, J. Chem. Phys. 118, 1634 (2003)] in order to directly target and selectively calculate those normal modes which have the largest effect on the vibronic band shape for a certain electronic excitation. This is achieved by defining a criterion for the importance of a normal mode to the vibrational progressions in the absorption band within the so-called "independent mode, displaced harmonic oscillator" (IMDHO) model. We use this approach for a vibronic-structure investigation for several small test molecules as well as for a comparison of the vibronic absorption spectra of a truncated chlorophyll a model and the full chlorophyll a molecule. We show that the method allows to go beyond the often-used strategy to simulate absorption spectra based on broadened vertical excitation peaks with just a minimum of computational effort, which in case of chlorophyll a corresponds to about 10% of the cost for a full simulation within the IMDHO approach.

  16. Vibronic-structure tracking: a shortcut for vibrationally resolved UV/Vis-spectra calculations.

    PubMed

    Barton, Dennis; König, Carolin; Neugebauer, Johannes

    2014-10-28

    The vibrational coarse structure and the band shapes of electronic absorption spectra are often dominated by just a few molecular vibrations. By contrast, the simulation of the vibronic structure even in the simplest theoretical models usually requires the calculation of the entire set of normal modes of vibration. Here, we exploit the idea of the mode-tracking protocol [M. Reiher and J. Neugebauer, J. Chem. Phys. 118, 1634 (2003)] in order to directly target and selectively calculate those normal modes which have the largest effect on the vibronic band shape for a certain electronic excitation. This is achieved by defining a criterion for the importance of a normal mode to the vibrational progressions in the absorption band within the so-called "independent mode, displaced harmonic oscillator" (IMDHO) model. We use this approach for a vibronic-structure investigation for several small test molecules as well as for a comparison of the vibronic absorption spectra of a truncated chlorophyll a model and the full chlorophyll a molecule. We show that the method allows to go beyond the often-used strategy to simulate absorption spectra based on broadened vertical excitation peaks with just a minimum of computational effort, which in case of chlorophyll a corresponds to about 10% of the cost for a full simulation within the IMDHO approach. PMID:25362280

  17. Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order harmonic generation

    PubMed Central

    Ferré, A.; Boguslavskiy, A. E.; Dagan, M.; Blanchet, V.; Bruner, B. D.; Burgy, F.; Camper, A.; Descamps, D.; Fabre, B.; Fedorov, N.; Gaudin, J.; Geoffroy, G.; Mikosch, J.; Patchkovskii, S.; Petit, S.; Ruchon, T.; Soifer, H.; Staedter, D.; Wilkinson, I.; Stolow, A.; Dudovich, N.; Mairesse, Y.

    2015-01-01

    High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20–26?eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected. PMID:25608712

  18. Anharmonic vibrational analysis of 3,4-diaminopyridine and 3-aminopyridine by density functional theory calculations.

    PubMed

    Karpagam, J; Sundaraganesan, N; Kalaichelvan, S; Sebastian, S

    2010-09-01

    In this work, we will report a combined experimental and theoretical study on molecular structure and vibrational analysis of 3,4-diaminopyridine (3,4-DAP) and 3-aminopyridine (3-AP). The Fourier transform infrared and Fourier transform Raman spectra of 3,4-DAP were recorded in the solid phase. The molecular geometry, harmonic vibrational wavenumbers of 3-AP and 3,4-DAP in the ground-state have been calculated by using MP2 and density functional methods (B3LYP) using 6-311++G(d,p) as basis set. Predicted electronic absorption spectra 3,4-DAP from TD-DFT calculation have been analyzed comparing with the experimental UV-vis spectrum. The calculated HOMO and LUMO energies show that charge transfer occur in the molecule. A detailed interpretation of the infrared spectra of 3-AP and 3,4-DAP is reported. The theoretical spectrograms for FTIR and FT-Raman spectra of the title molecules have also been constructed. Comparison of the experimental spectra with anharmonic vibrational wavenumbers indicates that B3LYP results are more accurate. PMID:20483656

  19. Suppressing harmonic vibrations of a miniature cryogenic cooler using an adaptive tunable vibration absorber based on magneto-rheological elastomers.

    PubMed

    Kim, Y-K; Koo, J H; Kim, K-S; Kim, S H

    2011-03-01

    This paper presents dynamic performances of an adaptive tunable vibration absorber (TVA) designed to suppress the main harmonic disturbance of a miniature linear cryogenic cooler, which is being used in space applications such as an observation satellite. The adaptive TVA employs a magneto-rheological elastomer (MRE) for a variable stiffness element. This study first investigates the shear modulus change of MRE samples with respect to the magnetic flux density, which varies through the alignment of particle chains. The MRE with the maximal shear modulus change is mounted for the TVA on a prototype cooler, which emulates the characteristics of a miniature cryogenic cooler. Using the test setup, a series of vibration tests are performed to evaluate the performance and efficacy of the MRE TVA and its re-tuning ability. The experimental results show that the MRE TVA is able to robustly suppress the vibration of the cooler even when the frequency of resonant vibration is changed up to 87% from its initial frequency. PMID:21456785

  20. Harmonic and Random Vibration Durability of SAC305 and Sn37Pb Solder Alloys

    Microsoft Academic Search

    Y. Zhou; M. Al-Bassyiouni; A. Dasgupta

    2010-01-01

    In this paper, durability tests were conducted on both SAC305 and Sn37Pb solder interconnects using both harmonic and random vibration. The test specimens consist of daisy-chained printed wiring boards (PWBs) with several different surface-mount component styles. Modal testing was first conducted on a test PWB to determine the natural frequencies and mode shapes. The PWB was then subjected to narrow-band

  1. Investigation of the vibration of a blade with friction damper by HBM. [Harmonic Balance Method

    SciTech Connect

    Wang, J.H.; Chen, W.K. (National Tsing Hua Univ., Hsinchu (Taiwan, Province of China))

    1993-04-01

    The friction damper has been widely used to reduce the resonant vibration of blades. The most commonly used methods for studying the dynamic behavior of a blade with a friction damper are direct integration methods. Although the harmonic balance method (HBM) is a well-known method for studying nonlinear vibration problems, generally only a one-term approximation has been proposed to study the nonlinear vibration of a frictionally damped blade. In this work, a HMB procedure with a multiterm approximation is proposed. The results show that the steady-state response and other related behavior of a frictionally damped blade can be predicted accurately and quickly by an HBM with a multiterm approximation.

  2. Calculations of the effect of nitrogen vibrational kinetics on laminar flame temperature profiles

    SciTech Connect

    Fisher, E.M. [Cornell Univ., Ithaca, NY (United States). Sibley School of Mechanical and Aerospace Engineering] [Cornell Univ., Ithaca, NY (United States). Sibley School of Mechanical and Aerospace Engineering

    1997-01-01

    Calculations of several premixed and nonpremixed laminar flames have been performed using two chemical kinetics mechanisms: (1) a vibrational kinetics mechanism treating nitrogen as a number of distinct species corresponding to different vibrational energy levels, with reactions representing transitions between energy levels; and (2) a traditional mechanism that treats nitrogen as being in vibrational equilibrium. In the vibrational kinetics calculations, translational/vibrational and vibrational/vibrational energy transfers are included, as is the effect of collisions with CO{sub 2} and H{sub 2}O on N{sub 2} vibrational excitation. Vibrational temperatures are calculated from the populations of various N{sub 2} species. For a stoichiometric, atmospheric-pressure premixed methane/air flame, the vibrational temperature is 40 K lower than the rotational/translational temperature in the region of high temperature gradient. The lag in filling upper vibrational energy levels of nitrogen also results in a lower effective heat capacity for the mixture in the vibrational kinetics case than in the vibrational equilibrium case. Rotational/translational temperatures exceed those calculated with the traditional mechanism by as much as 15 K in the region of steep temperature gradient. For diffusion flames over the range of strain rates investigated here, the effect of vibrational kinetics is much smaller. Sensitivity analysis indicates that, among the vibrational Kinetics reactions, the initial vibrational excitation of N{sub 2} by CO{sub 2} and H{sub 2}O has the greatest impact on the temperature results.

  3. Calculation of the vibrational spectra of betaine hydrochloride

    NASA Astrophysics Data System (ADS)

    Szafran, Miroslaw; Koput, Jacek

    1997-02-01

    The molecular geometries of betaine hydrochloride, BET·HCl, and free protonated betaine, BET·H +, were calculated with the 6-31G(d,p) basis set at the SCF, MP2 and DFT levels of theory. At the SCF level, the minimum energy corresponds to the ionic pair, B +Htctdot;A -, however, the equilibrium Otctdot;Cl distance is 0.14 Å shorter than the X-ray value. Inclusion of the correlation effects, both at the MP2 and DFT levels, predicts a minimum energy for the molecular complex, Btctdot;H-A, with the equilibrium Otctdot;Cl distance close to the experimental value. The frequencies and intensities of the vibrational bands of BET·HCl, BET·DCl and BET·H + were calculated at the SCF and DFT levels and compared with the solid IR spectra. All measured IR bands were interpreted in term of the calculated vibrational modes. The rms deviations between the experimental and calculated SCF frequencies were 21 and 29 cm -1 for BET·HCl and BET·DCl, respectively. The computed band intensities agree qualitatively with the experimental data. The coupling of the CO stretching and OH bending modes are discussed. The summation bands are probably enhanced in intensity by Fermi resonance with the fundamentals responsible for the main ?(OH) (?(OD) absorption region.

  4. A simplified approach for the calculation of acoustic emission in the case of friction-induced noise and vibration

    NASA Astrophysics Data System (ADS)

    Soobbarayen, K.; Besset, S.; Sinou, J.-. J.

    2015-01-01

    The acoustic response associated with squeal noise radiations is a hard issue due to the need to consider non-linearities of contact and friction, to solve the associated nonlinear dynamic problem and to calculate the noise emissions due to self-excited vibrations. In this work, the focus is on the calculation of the sound pressure in free space generated during squeal events. The calculation of the sound pressure can be performed by the Boundary Element Method (BEM). The inputs of this method are a boundary element model, a field of normal velocity characterized by a unique frequency. However, the field of velocity associated with friction-induced vibrations is composed of several harmonic components. So, the BEM equation has to be solved for each frequency and in most cases, the number of harmonic components is significant. Therefore, the computation time can be prohibitive. The reduction of the number of harmonic component is a key point for the quick estimation of the squeal noise. The proposed approach is based on the detection and the selection of the predominant harmonic components in the mean square velocity. It is applied on two cases of squeal and allows us to consider only few frequencies. In this study, a new method will be proposed in order to quickly well estimate the noise emission in free space. This approach will be based on an approximated acoustic power of brake system which is assumed to be a punctual source, an interpolated directivity and the decrease of the acoustic power levels. This method is applied on two classical cases of squeal with one and two unstable modes. It allows us to well reconstruct the acoustic power levels map. Several error estimators are introduced and show that the reconstructed field is close to the reference calculated with a complete BEM.

  5. Harmonic vibrations in two-dimensional graded elastic networks: Variety of normal modes and their transitions

    NASA Astrophysics Data System (ADS)

    Xiao, J. J.; Yakubo, K.; Yu, K. W.

    2006-06-01

    We study vibrational excitations in graded elastic networks modeled by coupled harmonic oscillators in a square lattice, in which the force constants or the vibrating masses can vary along one direction, i.e., the gradient direction. It turns out that the two-dimensional network under study can be reduced to a set of effective one-dimensional graded chains [Phys. Rev. B 73, 054201 (2006)] with additional on-site potentials. We identify various kinds of vibrational normal modes in these networks with graded force-constant (mass), namely, unbound modes and two types of confined modes called soft (heavy) and hard (light) “gradons” which reside at the two opposite edges of the network in the gradient direction. The transitions from gradons to unbound modes occur at specific frequencies ?c1(ks) and ?c2(ks) for each corresponding wave number ks in the transverse direction. While above the maximum of ?c2(ks) , pure hard (light) gradons exist, there is severe mixing of nondegenerate phonons and gradons below this frequency, showing intriguing zigzag inverse participation ratio. It is very interesting to see such unusual excitation modes that have adjacent eigenvalues but possess quite different spatial extents. The results reduce to the previously obtained one-dimensional results for ks=0 . The method is quite general and applicable to three-dimensional elastic networks. We conclude with discussions on how these new gradon modes may affect the macroscopic properties of graded solids. Our results can also be applied to analogous systems with graded character.

  6. Free vibration and forced harmonic response of an electrorheological fluid-filled sandwich plate

    NASA Astrophysics Data System (ADS)

    Hasheminejad, Seyyed M.; Maleki, Mohsen

    2009-05-01

    A dynamic model for the electric field-dependent steady-state vibrational response of a rectangular sandwich plate with a tunable electrorheological fluid (ERF) interlayer, subjected to a general harmonic transverse excitation, is developed. Hamilton's principle and the classical thin plate theory are applied to derive a set of fully coupled dynamic equations of motion along with the associated general boundary conditions. Assuming simply-supported edge conditions, the displacement components of the ERF-based sandwich plate are postulated by means of generalized double Fourier series with frequency-dependent coefficients. The natural frequencies and modal loss factors are subsequently determined by solving a complex eigenvalue problem. Analytical solutions are also obtained for the forced vibration characteristics of the adaptive structure under different external transverse excitations of varying frequency (0-300 Hz) and applied electric field strength (0-3.5 kV mm-1). Primary attention is focused on the effects of electric field magnitude, geometric aspect ratio, loading type, and ER core layer thickness on the dynamic characteristics of the sandwich plate. In addition, an effort is made to find the optimal electric field which yields minimized vibration amplitude for each excitation frequency. Limiting cases are considered and good agreements with the numerical solutions available in the literature are obtained.

  7. Mapping quadrupole collectivity in the Cd isotopes: The breakdown of harmonic vibrational motion

    SciTech Connect

    Garrett, P. E. [Department of Physics, University of Guelph, Guelph, Ontario, N1G2W1 (Canada); TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T2A3 (Canada); Green, K. L.; Bangay, J.; Varela, A. Diaz; Sumithrarachchi, C. S.; Bandyopadhyay, D. S.; Bianco, L.; Demand, G. A.; Finlay, P.; Grinyer, G. F.; Leach, K. G.; Phillips, A. A.; Schumaker, M. A.; Svensson, C. E.; Wong, J. [Department of Physics, University of Guelph, Guelph, Ontario, N1G2W1 (Canada); Austin, R. A. E.; Colosimo, S. [Department of Astronomy and Physics, Saint Mary's University, Halifax, Nova Scotia, B3H3C3 (Canada); Ball, G. C.; Garnsworthy, A. B.; Hackman, G. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T2A3 (Canada)

    2011-10-28

    The stable Cd isotopes have long been used as paradigms for spherical vibrational motion. Extensive investigations with in-beam {gamma} spectroscopy have resulted in very-well-established level schemes, including many lifetimes or lifetime limits. A programme has been initiated to complement these studies with very-high-statistics {beta} decay using the 8{pi} spectrometer at the TRIUMF radioactive beam facility. The decays of {sup 112}In and {sup 112}Ag have been studied with an emphasis on the observation of, or the placement of stringent limits on, low-energy branches between potential multi-phonon levels. A lack of suitable 0{sup +} or 2{sup +} three-phonon candidates has been revealed. Further, the sum of the B(E2) strength from spin 0{sup +} and 2{sup +} states up to 3 MeV in excitation energy to the assigned two-phonon levels falls far short of the harmonic-vibrational expectations. This lack of strength points to the failing of collective models based on vibrational phonon structures.

  8. Comparative Study on Calculation Methods of Blasting Vibration Velocity

    NASA Astrophysics Data System (ADS)

    Liang, Qingguo; An, Yafang; Zhao, Lei; Li, Dewu; Yan, Liping

    2011-01-01

    Due to the extreme complexities in rock blasting and difficulties in theoretical or numerical analysis, and the enormous consumption of explosives in mining and construction operations, empirical or semi-empirical formulae for blasting vibration velocity (BVV) were obtained from observations and measurements in field blast tests and are still widely used all over the world. This paper investigates the fitting degree and characteristics of several calculation methods for BVV based on 34 sets of data samples from 27 projects belonging to 4 types. The results indicate that both the cube-root scaling formula and the square-root scaling formula have relatively good fitting degree, while the multiple regression analysis can give the best fitting outcome if the sample space satisfies certain requirements. Whether the cube-root scaling formula or the square-root scaling formula is chosen to analyze the relationship between BVV and scaled distance depends on the average scaled distance under cubic-root scaling. If the average scaled distance is over 0.1, the cube-root scaling formula should be used; otherwise, the square-root scaling formula should be used. Bigger samples integrated from data samples of different projects but in the same type were then analyzed to get the empirical relations for different types of projects. The correlation coefficients of these relations are quite good, thus these relations can be used for reference in other similar projects. This paper then discusses the physical meanings of parameters in different formulae, sample selection and parameter choice for BVV. It suggests that the current calculation methods for explosive charge, blasting-to-monitoring distance and scaled distance need to be improved. It also concludes that the integrated BVV from velocity components in three-dimensions is more reasonable on a theoretical basis. It can yield good results in predicting the blasting vibration, and should be used as widely as possible.

  9. Sampling of semiclassically quantized polyatomic molecule vibrations by an adiabatic switching method: Application to quasiclassical trajectory calculations

    NASA Astrophysics Data System (ADS)

    Huang, Jingrong; Valentini, James J.; Muckerman, James T.

    1995-04-01

    We apply the adiabatic switching (AS) method to determine the polyatomic classical motions that correspond to selected vibrational quantum states on multidimensional, anharmonic potential energy surfaces, and use these semiclassically quantized motions as initial conditions for quasiclassical trajectory (QCT) calculations of state-to-state reaction dynamics. Specifically, we calculate the classical motion corresponding to the quantum mechanical zero-point vibration of deuterated methane, CD4, and run QCT calculations on the H+CD4?HD(v',j')+CD3 reaction. The distribution of CD4 vibrational zero-point energy (ZPE) associated with the AS-sampled motions is compared with that from normal-mode-sampled motions. The spread of total zero-point energy in the AS calculations is much narrower than with normal-mode sampling, and the ZPE's are appropriately shifted to lower energy due to anharmonic effects. Reverse adiabatic switching is used as an indirect check of the quantum numbers of the adiabatically sampled motion, but numerical limitations made this test inconclusive. The AS method thus appears to be superior to normal-mode sampling, but this superiority cannot be demonstrated conclusively for the fully anharmonic CD4 potential. However, the AS method is shown to perform very well for transformation from one CD4 harmonic potential to another and for transformation from an harmonic to an anharmonic, but decoupled potential in which CD4 is described by Morse oscillators. Evidence is presented that suggests the AS calculations are limited by numerical inaccuracies or intrinsic features of the potential energy surface, both of which are unavoidable. H+CD4?HD(v',j')+CD3 QCT calculations of state-to-state dynamics using CD4 with no ZPE, the ZPE from AS sampling, and the ZPE from normal-mode sampling are reported and compared.

  10. PHYSICAL REVIEW A 90, 063412 (2014) Effect of nuclear vibration on high-order-harmonic generation of aligned H2

    E-print Network

    Chu, Shih-I

    2014-01-01

    PHYSICAL REVIEW A 90, 063412 (2014) Effect of nuclear vibration on high-order-harmonic generation of aligned H2 + molecules Dmitry A. Telnov,1,* John Heslar,2, and Shih-I Chu2,3, 1 Department of Physics, St. Petersburg State University, St. Petersburg 198504, Russia 2 Department of Physics, Center for Quantum

  11. A study of coupled rotor-fuselage vibration with higher harmonic control using a symbolic computing facility

    NASA Technical Reports Server (NTRS)

    Papavassiliou, I.; Venkatesan, C.; Friedmann, P. P.

    1990-01-01

    A fundamental study of vibration prediction and vibration reduction in helicopters using active controls was performed. The nonlinear equations of motion for a coupled rotor/flexible fuselage system have been derived using computer algebra on a special purpose symbolic computing facility. The details of the derivation using the MACSYMA program are described. The trim state and vibratory response of the helicopter are obtained in a single pass by applying the harmonic balance technique and simultaneously satisfying the trim and the vibratory response of the helicopter for all rotor and fuselage degrees of freedom. The influence of the fuselage flexibility on the vibratory response is studied. It is shown that the conventional single frequency higher harmonic control (HHC) capable of reducing either the hub loads or only the fuselage vibrations but not both simultaneously. It is demonstrated that for simultaneous reduction of hub shears and fuselage vibrations a new scheme called multiple higher harmonic control (MHHC) is required. The fundamental aspects of this scheme and its uniqueness are described in detail, providing new insight on vibration reduction in helicopters using HHC.

  12. Vapor-phase Raman spectra, theoretical calculations, and the vibrational and structural properties of cis- and trans-stilbene.

    PubMed

    Egawa, Toru; Shinashi, Kiyoaki; Ueda, Toyotoshi; Ocola, Esther J; Chiang, Whe-Yi; Laane, Jaan

    2014-02-13

    The vapor-phase Raman spectra of cis- and trans-stilbene have been collected at high temperatures and assigned. The low-frequency skeletal modes were of special interest. The molecular structures and vibrational frequencies of both molecules have also been obtained using MP2/cc-pVTZ and B3LYP/cc-pVTZ calculations, respectively. The two-dimensional potential map for the internal rotations around the two Cphenyl-C(?C) bonds of cis-stilbene was generated by using a series of B3LYP/cc-pVTZ calculations. It was confirmed that the molecule has only one conformer with C2 symmetry. The energy level calculation with a two-dimensional Hamiltonian was carried out, and the probability distribution for each level was obtained. The calculation revealed that the "gearing" internal rotation in which the two phenyl rings rotate with opposite directions has a vibrational frequency of 26 cm(-1), whereas that of the "antigearing" internal rotation in which the phenyl rings rotate with the same direction is about 52 cm(-1). In the low vibrational energy region the probability distribution for the gearing internal rotation is similar to that of a one-dimensional harmonic oscillator, and in the higher region the motion behaves like that of a free rotor. PMID:24409818

  13. Harmonic Vibrations and Thermodynamic Stability of a DNA Oligomer in Monovalent Salt Solution

    NASA Astrophysics Data System (ADS)

    Garcia, Angel E.; Soumpasis, Dikeos Mario

    1989-05-01

    We compute the full harmonic vibrational spectrum and eigenmodes of a DNA oligomer, d(C-G)3, in optimized B and Z conformations in various ionic environments (0.01-5.0 M NaCl). The statistical interactions of DNA with the diffuse ionic cloud surrounding it in solution are approximately represented within the potential of mean force framework. The lowest eigenfrequency of the B conformation is found to drastically decrease with increased NaCl concentration. This suggests that a soft mode mechanism may be a precursor for the B-to-Z conversion. The free energy balance governing the B-Z isomerization of d(C-G)3 is dominated by the solvent-averaged effective phosphate-phosphate interactions due to substantial cancelations between the much larger intramolecular energy contributions.

  14. Problems needing attention in calculation of emission limit of customer's harmonic current

    Microsoft Academic Search

    Bai Jianxun; Yang Honggeng

    2011-01-01

    There are strict limits provisions for the harmonic currents produced by distorting loads connected to the point of common coupling, the national standard GB\\/T14549-93 and IEC technical documents 61000-3-6 have given the limits for harmonic emission calculation methods. This paper describes these two calculation methods, the coincidence factor of high load distortion both in detail. This paper analyses and ascertains

  15. Spectral Analysis of Vibrational Harmonic Motion by use of a Continuous-Wave CO2 Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Jarzembski, Maurice A.; Srivastava, Vandana

    1999-01-01

    Vibrational motion of a harmonic oscillator was investigated using a focused continuous wave CO2 Doppler lidar at 9.1 microns wavelength. A continuum of frequencies along with many discrete, equally spaced, resonant frequency modes was observed. The frequency modes are similar in structure to the oscillatory longitudinal modes of a laser cavity and arise because of interference of the natural resonant frequency of the oscillator with specific frequencies within the continuum. The spectra revealed departures from linear motion for vigorous vibrations of the oscillator. Each consecutive resonant frequency mode occurred for a movement of the oscillator much less than the wavelength of incident lidar radiation.

  16. Extra Low-Frequency Terrestrial Radio-Wave Field Calculations with the Zonal Harmonics Series

    Microsoft Academic Search

    J. Ralph Johler; Richard L. Lewis

    1969-01-01

    Use of the zonal harmonics series for calculating the terrestrial wave guide fields directly is described. The analysis is extended to include radio waves propagating into sea water or below the earth's surface. A sample calculation of ELF radio waves is analyzed into a direct wave and a wave that has traveled the circumference of the earth. The location of

  17. Vanillin and isovanillin: Comparative vibrational spectroscopic studies, conformational stability and NLO properties by density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Balachandran, V.; Parimala, K.

    This study is a comparative analysis of FT-IR and FT-Raman spectra of vanillin (3-methoxy-4-hydroxybenzaldehyde) and isovanillin (3-hydroxy-4-methoxybenzaldehyde). The molecular structure, vibrational wavenumbers, infrared intensities, Raman scattering activities were calculated for both molecules using the B3LYP density functional theory (DFT) with the standard 6-311++G?? basis set. The computed values of frequencies are scaled using multiple scaling factors to yield good coherence with the observed values. The calculated harmonic vibrational frequencies are compared with experimental FT-IR and FT-Raman spectra. The geometrical parameters and total energies of vanillin and isovanillin were obtained for all the eight conformers (a-h) from DFT/B3LYP method with 6-311++G?? basis set. The computational results identified the most stable conformer of vanillin and isovanillin as in the "a" form. Non-linear properties such as electric dipole moment (?), polarizability (?), and hyperpolarizability (?) values of the investigated molecules have been computed using B3LYP quantum chemical calculation. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecules.

  18. A hybrid variational-perturbation calculation of the ro-vibrational spectrum of nitric acid

    E-print Network

    Pavlyuchko, A I; Tennyson, Jonathan

    2014-01-01

    Rotation-vibration spectra of the nitric acid molecule, HNO\\3, are calculated for wavenumbers up to 7000~\\cm. Calculations are performed using a Hamiltonian expressed in internal curvilinear vibrational coordinates solved using a hybrid variational-perturbation method. An initial potential energy surface (PES) and dipole moment function (DMF) are calculated {\\it ab initio} at the CCSD(T)/aug-cc-pVQZ level of theory. Parameters of the PES and DMF are varied to minimize differences between the calculated and experimental transition frequencies and intensities. The average, absolute deviation between calculated and experimental values is 0.2~\\cm\\ for frequencies in the fundamental bands and 0.4~\\cm\\ for those in the first overtone and lowest combination bands. For the intensities, the calculated and experimental values differ by 0.3\\% and 40\\% for the fundamentals and overtones, respectively. The optimized PES and DMF are used to calculate the room-temperature ro-vibrational spectrum. These calculation reproduce...

  19. Harmonic Vibrational Frequencies:  An Evaluation of Hartree?Fock, Møller?Plesset, Quadratic Configuration Interaction, Density Functional Theory, and Semiempirical Scale Factors

    Microsoft Academic Search

    Anthony P. Scott; Leo Radom

    1996-01-01

    Scaling factors for obtaining fundamental vibrational frequencies, low-frequency vibrations, zero-point vibrational energies (ZPVE), and thermal contributions to enthalpy and entropy from harmonic frequencies determined at 19 levels of theory have been derived through a least-squares approach. Semiempirical methods (AM1 and PM3), conventional uncorrelated and correlated ab initio molecular orbital procedures (Hartree- Fock (HF), Møller-Plesset (MP2), and quadratic configuration interaction including

  20. Microwave, structural, conformational, vibrational studies and ab initio calculations of fluoroacetyl chloride.

    PubMed

    Deodhar, Bhushan S; Brenner, Reid E; Klaassen, Joshua J; Tubergen, Michael J; Durig, James R

    2015-09-01

    The infrared and Raman spectra (3200-50cm(-1)) of the gas, liquid or solution, and solid of fluoroacetyl chloride, FCH2COCl have been recorded. FT-microwave studies have also been carried out and 22 transitions were recorded for the trans conformer. Variable temperature (-50 to -105°C) studies of the infrared and Raman spectra (3200-50cm(-1)) of xenon solutions have been carried out. From these data, the trans, cis and gauche conformers have been identified and their relative stabilities obtained. The enthalpy difference has been determined to be 159±11cm(-1) (1.90±0.14kJmol(-1)) with the trans conformer the more stable form than the cis. The energy difference between the cis and gauche form is 222±18cm(-1) (2.66±0.21kJ/mol) and the energy difference between the trans and gauche forms is 386±13cm(-1) (4.61±0.16kJ/mol). Vibrational assignments have been made for the observed bands for the three conformers with initial predictions by MP2(full)/6-31G(d) ab initio calculations to obtain harmonic force constants, wavenumbers, infrared intensities, and Raman activities for the three conformers. By utilizing the microwave rotational constants of two isotopomers for trans, combined with the structural parameters predicted from MP2(full)/6-311+G(d,p) calculations, adjusted r0 parameters have been obtained for the trans conformer. The results are discussed and compared to the corresponding properties of some related molecules. PMID:25909903

  1. Molecular structure, vibrational analysis (FT-IR, FT-Raman), NMR, UV, NBO and HOMO-LUMO analysis of N,N-Diphenyl Formamide based on DFT calculations

    NASA Astrophysics Data System (ADS)

    Mathammal, R.; Monisha, N. R.; Yasaswini, S.; Krishnakumar, V.

    2015-03-01

    In this work, the vibrational spectral analysis is carried out by using Raman and infrared spectroscopy in the range 4000-400 cm-1 and 4000-50 cm-1 respectively for N,N-Diphenyl Formamide (DPF) molecule. The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments, nuclear magnetic resonance (NMR) and ultraviolet-visible (UV-VIS) spectra of the title molecule are evaluated using density functional theory (DFT) with standard B3LYP/6-31G(d, p) basis set. The harmonic vibrational frequencies are calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. The stability of the molecule arising from hyper conjugative interactions and the charge delocalization has been analyzed using natural bond (NBO) analysis. The possible electronic transitions are determined by HOMO-LUMO orbital shapes and their energies. Thermodynamic properties (heat capacity, entropy and enthalpy) and the first hyperpolarizability of the title compound are calculated. The Mulliken charges and electric dipole moment of the molecule are computed using DFT calculations. The 1H and 13C nuclear magnetic resonance (NMR) chemical shift of the molecules are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.

  2. FT-IR and FT-Raman vibrational assignment of 2-bromobenzoic acid with the help of ab initio and DFT calculations

    NASA Astrophysics Data System (ADS)

    Swaminathan, J.; Ramalingam, M.; Saleem, H.; Sethuraman, V.; Ameen, M. T. Noorul

    2009-12-01

    The vibrational spectra of 2-bromobenzoic acid (2BBA) have been experimentally recorded (FT-IR and FT-Raman) and compared with the harmonic vibrational frequencies calculated at HF and B3LYP level of theories using 6-311+G(d,p) basis set with appropriate scaling factors. The XRD geometrical parameters show satisfactory agreement with the theoretical prediction at Hartree-Fock and B3LYP levels. The scaled vibrational frequencies at B3LYP/6-311+G(d,p) seem to coincide with the experimentally observed values with acceptable deviations. The theoretical spectrograms (IR and Raman) have been constructed and compared with the experimental FT-IR and FT-Raman spectra.

  3. Acoustic noise, vibration, harmonics, thermal of three phase linear switched reluctance machines

    Microsoft Academic Search

    N. C. Lenin; R. Arumugam

    2010-01-01

    Acoustic noise in the linear switched reluctance motor (LSRM) is caused primarily by the deformation of the stator lamination stack. Acoustic noise is most severe when the periodic excitation of the LSRM phases excites a natural vibration mode of the stack. Noise and vibration are usually high in LSRM because of doubly salient structures. The natural vibration modes and frequencies

  4. Quantum-chemical calculations of the structure and vibration spectrum of methyl nitrate

    NASA Astrophysics Data System (ADS)

    Shaikhullina, R. M.; Khrapkovskii, G. M.; Sarvarov, F. S.

    2014-12-01

    Methyl nitrate vibration spectra theoretical analysis data within the B3LYP density functional theory method in the 6 -31G (d) basis are represented. When optimizing the geometry of the molecule it was found out that methyl nitrate is characterized by one stable conformation: trans – form. Frequency, intensity and forms of normal vibrations are calculated, their comparative analysis with well-known from the literature experimental data is given.

  5. Calculation of vibrational spectra of an icosahedral quasicrystal AlCuFe

    SciTech Connect

    Rudenko, A. N., E-mail: ran@infoteck.ru; Mazurenko, V. G. [Ural State University (Russian Federation)

    2007-11-15

    Vibrational spectra of an icosahedral quasicrystal AlCuFe have been calculated on the basis of a crystalline 1/1 approximant by the recurrence method. To describe the interaction of atoms in a quasicrystal, the semiempirical EAM model was used. It is shown that the calculated spectra are in satisfactory agreement with the experimental neutron inelastic scattering data.

  6. Calculation of Rdx Molecular Crystal Geometry and Vibrational Frequencies Under Hydrostatic Pressure

    NASA Astrophysics Data System (ADS)

    Slough, W. J.; Perger, W. F.

    2007-12-01

    First-principles calculations of the effects of hydrostatic pressure on RDX are performed using the all-electron CRYSTAL06 program. The lattice constants and optimized internal coordinates are simultaneously obtained at ambient pressure and hydrostatic pressure up to 2.9 GPa. The vibrational frequencies as a function of pressure are also calculated and compared with experimental results from the literature.

  7. A hybrid variational-perturbation calculation of the ro-vibrational spectrum of nitric acid.

    PubMed

    Pavlyuchko, A I; Yurchenko, S N; Tennyson, Jonathan

    2015-03-01

    Rotation-vibration spectra of the nitric acid molecule, HNO3, are calculated for wavenumbers up to 7000 cm(-1). Calculations are performed using a Hamiltonian expressed in internal curvilinear vibrational coordinates employing a hybrid variational-perturbation method. An initial potential energy surface (PES) and dipole moment function (DMF) are calculated ab initio at the CCSD(T)/aug-cc-pVQZ level of theory. Parameters of the PES and DMF are varied to minimize differences between the calculated and experimental transition frequencies and intensities. The average, absolute deviation between calculated and experimental values is 0.2 cm(-1) for frequencies in the fundamental bands and 0.4 cm(-1) for those in the first overtone and lowest combination bands. For the intensities, the calculated and experimental values differ by 0.3% and 40% for the fundamentals and overtones, respectively. The optimized PES and DMF are used to calculate the room-temperature ro-vibrational spectrum. These calculation reproduce both the form of the absorption bands and fine details of the observed spectra, including the rotational structure of the vibrational bands and the numerous hot absorption band. Many of these hot bands are found to be missing from the compilation in HITRAN. A room temperature line list comprising 2 × 10(9) lines is computed. PMID:25747083

  8. Calculation of RDX molecular crystal geometry and vibrational frequencies under hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Perger, Warren; Slough, Wil

    2007-06-01

    First-principles calculations of the effects of hydrostatic pressure on RDX are performed using the all-electron CRYSTAL06 program. The lattice constants and optimized internal co-ordinates are simulanteously obtained at ambient pressure and hydrostatic pressure up to 4 GPa. A variety of density functionals and basis sets are used and presented for comparison. The vibrational frequencies as a function of pressure are also calculated and compared with previous gas-phase calculations.

  9. Lattice Monte Carlo calculations for unitary fermions in a harmonic trap

    SciTech Connect

    Endres, Michael G.; Kaplan, David B.; Lee, Jong-Wan; Nicholson, Amy N. [Physics Department, Columbia University, New York, New York 10027 (United States); Theoretical Research Division, RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550 (United States)

    2011-10-15

    We present a lattice Monte Carlo approach developed for studying large numbers of strongly interacting nonrelativistic fermions and apply it to a dilute gas of unitary fermions confined to a harmonic trap. In place of importance sampling, our approach makes use of high statistics, an improved action, and recently proposed statistical techniques. We show how improvement of the lattice action can remove discretization and finite volume errors systematically. For N=3 unitary fermions in a box, our errors in the energy scale as the inverse lattice volume, and we reproduce a previous high-precision benchmark calculation to within our 0.3% uncertainty; as additional benchmarks we reproduce precision calculations of N=3,...,6 unitary fermions in a harmonic trap to within our {approx}1% uncertainty. We then use this action to determine the ground-state energies of up to 70 unpolarized fermions trapped in a harmonic potential on a lattice as large as 64{sup 3}x72. In contrast to variational calculations, we find evidence for persistent deviations from the thermodynamic limit for the range of N considered.

  10. Monochromator harmonic content measurements and calculations at energies above 20 keV

    SciTech Connect

    Chapman, D.; Moulin, H.; Garrett, R.F.

    1991-01-01

    Measurements of the harmonic content from single and double crystal silicon monochromators have been made in the 20 to 100 keV at the X17 Superconducting Wiggler Beamline at the NSLS. These measurements are compared with calculations which estimate the monochromatic beam harmonic content and the detection system efficiency with good agreement. At high photon energies ( > 20keV), the scattering of x-rays from an amorphous scatterer is dominated by the inelastic Compton process. At large scattering angles this will completely overwhelm the more forward directed elastic scattering. The Compton x-ray energy shift is large enough to make the distinction between elastic and Compton scattering unambiguous when a spectrum is acquired with a solid state detector. This shift, which is energy dependent, allows the measurement of the relative harmonic intensity in a way that is not affected by pulse pileup in the detector and electronics. The present measurements were done to assess the level of harmonic contamination from two monochromator systems both used on the X17 beamline: the single crystal type monochromator for the Digital Subtraction Coronary Angiography project; and the double crystal monochromator being developed for the Multiple Energy Computed Tomography (MECT) project and the Materials Science program. 5 refs.

  11. Vibrational dynamics of DNA. III. Molecular dynamics simulations of DNA in water and theoretical calculations of the two-dimensional vibrational spectra

    Microsoft Academic Search

    Chewook Lee; Kwang-Hee Park; Jin-A. Kim; Seungsoo Hahn; Minhaeng Cho

    2006-01-01

    A theoretical description of the vibrational excitons in DNA is presented by using the vibrational basis mode theory developed in Papers I and II. The parameters obtained from the density functional theory calculations, such as vibrational coupling constants and basis mode frequencies, are used to numerically simulate two-dimensional (2D) IR spectra of dGn:dCn and dAn:dTn double helices with n varying

  12. Calculation of optical second-harmonic susceptibilities and optical activity for crystals

    SciTech Connect

    Levine, Z.H. [Ohio State Univ., Columbus, OH (United States)

    1994-12-31

    A new generation of nearly first-principles calculations predicts both the linear and second-harmonic susceptibilities for a variety of insulating crystals, including GaAs, GaP, AlAs, AlP, Se, {alpha}-quartz, and c-urea. The results are typically in agreement with experimental measurements. The calculations have been extended to optical activity, with somewhat less success to date. The theory, based on a simple self-energy correction to the local density approximation, and results are reviewed herein.

  13. Revised calculation of four-particle harmonic-oscillator transformation brackets matrix

    NASA Astrophysics Data System (ADS)

    Mickevi?ius, S.; Germanas, D.; Kalinauskas, R. K.

    2013-02-01

    In this article we present a new, considerably enhanced and more rapid method for calculation of the matrix of four-particle harmonic-oscillator transformation brackets (4HOB). The new method is an improved version of 4HOB matrix calculations which facilitates the matrix calculation by finding the eigenvectors of the 4HOB matrix explicitly. Using this idea the new Fortran code for fast and 4HOB matrix calculation is presented. The calculation time decreases more than a few hundred times for large matrices. As many problems of nuclear and hadron physics structure are modeled on the harmonic oscillator (HO) basis our presented method can be useful for large-scale nuclear structure and many-particle identical fermion systems calculations. Program summaryTitle of program: HOTB_M Catalogue identifier: AEFQ_v3_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFQ_v3_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 2149 No. of bytes in distributed program, including test data, etc.: 17576 Distribution format: tar.gz Programming language: Fortran 90. Computer: Any computer with Fortran 90 compiler. Operating system: Windows, Linux, FreeBSD, True64 Unix. RAM: Up to a few Gigabytes (see Tables 1 and 2 included in the distribution package) Classification: 17.16, 17.17. Catalogue identifier of previous version: AEFQ_v2_0 Journal reference of previous version: Comput. Phys. Comm. 182(2011)1377 Does the new version supersede the previous version?: Yes Nature of problem: Calculation of the matrix of the 4HOB in a more effective way, which allows us to calculate the matrix of the brackets up to a few hundred times more rapidly than in a previous version. Solution method: The method is based on compact expressions of 4HOB, presented in [1] and its simplifications presented in this paper. Reasons for new version: We facilitated the calculation of the 4HOB, based on the method presented in the section 'Theoretical aspects'. The new program version gives shorter calculation times for the 4HOB Summary of revisions: New subroutines for calculation of the matrix of the 4HOB. For theoretical issues of revision see the section 'Theoretical aspects'. Restrictions: The 4HOB matrices up to e=28. Running time: Depends on the dimension of the 4HOB matrix (see Tables 1 and 2 included in the distribution file). References: [1] D. Germanas, S. Mickevicius, R.K. Kalinauskas, Calculation of four-particle harmonic-oscillator transformation brackets, Computer Physics Communications 181, 420-425 (2010).

  14. Calculation of the vibrational spectra of betaine hydrochloride

    Microsoft Academic Search

    Miroslaw Szafran; Jacek Koput

    1997-01-01

    The molecular geometries of betaine hydrochloride, BET·HCl, and free protonated betaine, BET·H+, were calculated with the 6–31G(d,p) basis set at the SCF, MP2 and DFT levels of theory. At the SCF level, the minimum energy corresponds to the ionic pair, B+Htctdot;A?, however, the equilibrium Otctdot;Cl distance is 0.14 Å shorter than the X-ray value. Inclusion of the correlation effects, both

  15. Vibrational spectroscopy [FTIR and FTRaman] investigation, computed vibrational frequency analysis and IR intensity and Raman activity peak resemblance analysis on 4-chloro 2-methylaniline using HF and DFT [LSDA, B3LYP and B3PW91] calculations.

    PubMed

    Ramalingam, S; Periandy, S

    2011-03-01

    In the present study, the FT-IR and FT-Raman spectra of 4-chloro-2-methylaniline (4CH2MA) have been recorded in the range of 4000-100 cm(-1). The fundamental modes of vibrational frequencies of 4CH2MA are assigned. All the geometrical parameters have been calculated by HF and DFT (LSDA, B3LYP and B3PW91) methods with 6-31G (d, p) and 6-311G (d, p) basis sets. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values for aniline and some substituted aniline. The harmonic and anharmonic vibrational wavenumbers, IR intensities and Raman activities are calculated at the same theory levels used in geometry optimization. The calculated frequencies are scaled and compared with experimental values. The scaled vibrational frequencies at LSDA/B3LYP/6-311G (d, p) seem to coincide with the experimentally observed values with acceptable deviations. The impact of substitutions on the benzene structure is investigated. The molecular interactions between the substitutions (Cl, CH(3) and NH(2)) are also analyzed. PMID:21237700

  16. Elucidating low-frequency vibrational dynamics in calcite and water with time-resolved third-harmonic generation spectroscopy.

    PubMed

    Wang, Liang; Liu, Weimin; Fang, Chong

    2015-06-24

    Low-frequency vibrations are foundational for material properties including thermal conductivity and chemical reactivity. To resolve the intrinsic molecular conformational dynamics in condensed phase, we implement time-resolved third-harmonic generation (TRTHG) spectroscopy to unravel collective skeletal motions in calcite, water, and aqueous salt solution in situ. The lifetime of three Raman-active modes in polycrystalline calcite at 155, 282 and 703 cm(-1) is found to be ca. 1.6 ps, 1.3 ps and 250 fs, respectively. The lifetime difference is due to crystallographic defects and anharmonic effects. By incorporating a home-built wire-guided liquid jet, we apply TRTHG to investigate pure water and ZnCl2 aqueous solution, revealing ultrafast dynamics of water intermolecular stretching and librational bands below 500 cm(-1) and a characteristic 280 cm(-1) vibrational mode in the ZnCl4(H2O)2(2-) complex. TRTHG proves to be a compact and versatile technique that directly uses the 800 nm fundamental laser pulse output to capture ultrafast low-frequency vibrational motion snapshots in condensed-phase materials including the omnipresent water, which provides the important time dimension to spectral characterization of molecular structure-function relationships. PMID:26062639

  17. Lattice Monte Carlo calculations for unitary fermions in a harmonic trap

    E-print Network

    Michael G. Endres; David B. Kaplan; Jong-Wan Lee; Amy N. Nicholson

    2011-11-03

    We present a new lattice Monte Carlo approach developed for studying large numbers of strongly interacting nonrelativistic fermions, and apply it to a dilute gas of unitary fermions confined to a harmonic trap. Our lattice action is highly improved, with sources of discretization and finite volume errors systematically removed; we are able to demonstrate the expected volume scaling of energy levels of two and three untrapped fermions, and to reproduce the high precision calculations published previously for the ground state energies for N = 3 unitary fermions in a box (to within our 0.3% uncertainty), and for N = 3, . . ., 6 unitary fermions in a harmonic trap (to within our ~ 1% uncertainty). We use this action to determine the ground state energies of up to 70 unpolarized fermions trapped in a harmonic potential on a lattice as large as 64^3 x 72; our approach avoids the use of importance sampling or calculation of a fermion determinant and employs a novel statistical method for estimating observables, allowing us to generate ensembles as large as 10^8 while requiring only relatively modest computational resources.

  18. Floquet calculation of high harmonic generation from hydrogen molecular ions in monochromatic strong laser fields

    NASA Astrophysics Data System (ADS)

    Tsednee, Tsogbayar; Horbatsch, Marko

    2014-05-01

    We extended previous Floquet calculations to obtain high harmonic generation (HHG) for the lowest two electronic states of the H 2 + ion by strong continuous-wave laser fields. We solve the non-hermitean matrix problem to get accurate solutions to the time-dependent Schrödinger equation (TDSE) by applying a pseudospectral representation combined with a complex absorbing potential method. This represents an alternative approach to direct TDSE solutions to obtain the harmonic generation spectra for the ion. We compare our results for the HHG rate for the lower and upper states for the H 2 + ion, which correspond to gerade and ungerade states in the field-free case, with previously obtained results in the literature. We show that the enhancement of the ionization rates at critical internuclear separations Rc cause an enhancement of the HHG rates for the lower and upper states. Supported by NSERC, Canada.

  19. Calculations for shortening the bunch length in storage rings using a harmonic cavity

    NASA Astrophysics Data System (ADS)

    Fan, Hao; Wu, Cong-Feng; He, Duo-Hui

    2014-08-01

    Using the Hefei Light Source phase II project (HLS- II) as an example, a theoretical analysis of shortening the bunch lengths using a higher harmonic cavity (HHC) is given. The threshold voltage of an active HHC and the threshold tuning angle of a passive HHC are first analysed. The optimum tuning angle for the constant detuning scenario and the optimum harmonic voltage for the constant voltage scenario are presented. The calculated results show that the reduced bunch length is about half that of the nominal bunch. The bunch lengths vary from 11 mm at 0.1 A to 7 mm at 0.4 A for the constant detuning scenario, while the bunch lengths are around 7 mm over the beam current range for the constant voltage scenario. In addition, the synchrotron frequency spread is increased. It indicates that HHC may be used to reduce the bunch length and increase the Landau damping of synchrotron oscillations in a storage ring.

  20. Calculations of operating schemes for a passive harmonic cavity in HLS- II

    NASA Astrophysics Data System (ADS)

    Fan, Hao; Wu, Cong-Feng; Liu, Guang-Chao

    2012-09-01

    A passive higher harmonic cavity (HHC) will be used in the Hefei Light Source II Project (HLS- II) to lengthen the bunch and consequently increase the beam lifetime dominated by Touschek scattering. The effects of constant voltage and constant detuning have been calculated and compared over the operating current from 0.4 to 0.2 A on the bunch lengthening for the passive normal conducting harmonic cavity system in HLS- II. The results show that the bunch shape has less change and the lifetime improvement factors are not less than 2.7 over the beam currents for the constant voltage case. The constant voltage operating scheme may be applied to our machine.

  1. Ab initio calculation of harmonic generation spectra of helium using a time-dependent non-Hermitian formalism

    SciTech Connect

    Gilary, Ido; Moiseyev, Nimrod [Department of Chemistry and Minerva Center for Nonlinear Physics of Complex Systems, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Kapralova-Zd'anska, Petra R. [Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo 2, 166 10 Prague 6 (Czech Republic)

    2006-11-15

    The high harmonic spectra of helium atoms which are exposed to external monochromatic linearly polarized laser fields are calculated by solving the time-dependent non-Hermitian Schroedinger equation. The entire electronic correlation effects with and without the presence of the field are included in our calculations. The full high-harmonic generation spectra (HGS) were calculated (and not only the intensities of the integer harmonics frequencies as calculated before by non-Hermitian quantum mechanics). The HGS were calculated when the helium atoms are initially in their ground state, or in the 1s2p excited state or in a superposition of the two field free states. In the first two cases only odd-order harmonics are obtained. However, in the latter, in addition to the odd-order harmonics also pronounced even-order harmonics are obtained. The even order peaks are much broader than the peaks of the odd-order high harmonics. The association of the widths of the peaks in the HGS with the lifetime of the photoinduced resonances which control the dynamics is discussed.

  2. Calculation and interpretation of the vibrational spectrum of 2,2,6,6-tetramethyl-1-oxylpiperidine

    Microsoft Academic Search

    L. A. Kotorlenko; V. S. Aleksandrova; S. A. Samoilenko

    1979-01-01

    It might be expected that the replacement of the CH 3 groups by point masses would result in a certain discrepancy between the calculated and observed frequencies for the skeletal modes of the ring, and also possibly in the C-H frequencies. This discrepancy occurs for the C-CH 3 vibrations of radical H (Table 1) and agrees with the difference we

  3. Method for calculating the induced voltage in a vibrating sample magnetometer detection coil system

    Microsoft Academic Search

    Xiaonong Xu; Aimin Sun; Xin Jin; Hongchang Fan; Xixian Yao

    1996-01-01

    A numerical method for obtaining the vibrating sample magnetometer (VSM) sensitivity functions due to a uniformly magnetized sample in the shape of ellipsoid, cuboid or cylinder, and then calculating the induced voltage in a VSM detection coil systems is presented. The induced voltage, which depends on the equilibrium position and amplitude of the sample in three-dimensional space, and depends on

  4. The Calculation of Electrical Parameters of Film Bulk Acoustic Wave Resonators from Vibrations of Layered

    E-print Network

    Wang, Ji

    in the design and modeling of piezoelectric acoustic wave resonators of layered plates, especiallyThe Calculation of Electrical Parameters of Film Bulk Acoustic Wave Resonators from Vibrations-mail: {wangji, dujianke, huangdejin}@nbu.edu.cn, jiansongliu@163.com Abstract--Film bulk acoustic wave

  5. Calculation of the vibrational spectra of ?-rdx using the grimme DFT potential

    NASA Astrophysics Data System (ADS)

    Perger, Warren; Slough, William J.; Valenzano, Loredana; Flurchick, K. M.

    2012-03-01

    The density-functional theory (DFT) potential by Grimme has been proposed for describing longrange dispersion corrections. This potential has been implemented into the CRYSTAL09 program and used to calculate the vibrational spectra in ?-RDX at equilibrium. The frequencies and intensities are reported and compared with prior theory and experiment where possible.

  6. The effect of a simulated volumetric expansion: Calculated vibrational properties and elastic constants of pentaerythritol

    NASA Astrophysics Data System (ADS)

    Criswell, Jackson; Perger, Warren; Flurchick, K. M.; Valenzano, Loredana; Slough, William J.

    2012-03-01

    Current ab-initio calculations do not include the van der Waals interactions. These long range forces are important in the binding of many molecular crystals. Using current theory one may include empirical van der Waals forces to describe the binding of a molecular solid. The results of ab-initio calculations are at 0K. But, experiments measuring material properties are often at ambient conditions. The exclusion of thermal effects produces an inherent disparity between measurements and first-principles calculations of physical properties. In this work, the vibrational spectra and second-order elastic constants (SOECs) of pentaerythritol (PE) are found using density functional theory (DFT) with the B3LYP-D* functional. B3LYP-D* is the B3LYP functional with an empirical description of the van derWaals dispersion force. PE is chosen because it has a small, highly symmetric, unit cell and exhibits anisotropic binding. Also, recent experimental and theoretical vibrational studies show an interesting behavior of the OH-stretch mode for PE. Using DFT, the SOECs and vibrational spectra of PE are calculated at 0K. The volumetric expansion to ambient temperature is simulated by fixing the unit cell to an experimental volume, optimizing the structure, and recalculating properties. Results of elastic and vibrational properties for 0K, simulated ambient temperature, and experiment are compared.

  7. The effect of a simulated volumetric expansion: Calculated vibrational properties and elastic constants of pentaerythritol

    NASA Astrophysics Data System (ADS)

    Criswell, J.; Perger, W.; Slough, W.; Valenzano, L.

    2011-06-01

    Current ab-initio calculations do not include the van der Waal's interactions. These long range forces are important in the binding of many molecular crystals. Using current theory one may include empirical van der Waal's forces to describe the binding of a molecular solid. The results of ab-initio calculations are at 0K. But, experiments measuring material properties are often at ambient conditions. The exclusion of thermal effects produces an inherent disparity between measurements and first-principles calculations of physical properties. In this work, the vibrational spectra and second-order elastic constants (SOECs) of pentaerythritol (PE) are found using density functional theory (DFT) with the B3LYP-D* functional. B3LYP-D* is the B3LYP functional with an empirical description of the van der Waal's dispersion force. PE is chosen because it has a small, highly symmetric, unit cell and exhibits anisotropic binding. Also, recent experimental and theoretical vibrational studies show an interesting behavior of the OH-stretch mode for PE. Using DFT, the SOECs and vibrational spectra of PE are calculated at 0K. The volumetric expansion to ambient temperature is simulated by fixing the unit cell to an experimental volume, optimizing the structure, and recalculating properties. Results of elastic and vibrational properties for 0K, simulated ambient temperature, and experiment are compared. Supported by: ONR-MURI grant N00014-06-1-0459.

  8. Calculations of lattice vibrational mode lifetimes using Jazz: a Python wrapper for LAMMPS

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Wang, H.; Daw, M. S.

    2015-06-01

    Jazz is a new python wrapper for LAMMPS [1], implemented to calculate the lifetimes of vibrational normal modes based on forces as calculated for any interatomic potential available in that package. The anharmonic character of the normal modes is analyzed via the Monte Carlo-based moments approximation as is described in Gao and Daw [2]. It is distributed as open-source software and can be downloaded from the website http://jazz.sourceforge.net/.

  9. Anharmonic vibrational calculations modeling the raman spectra of intermediates in the photoactive yellow protein (PYP) photocycle.

    PubMed

    Adesokan, Adeyemi A; Pan, Duohai; Fredj, Erick; Mathies, Richard A; Gerber, R Benny

    2007-04-18

    The role of anharmonic effects in the vibrational spectroscopy of the dark state and two major chromophore intermediates of the photoactive yellow protein (PYP) photocycle is examined via ab initio vibrational self-consistent field (VSCF) calculations and time-resolved resonance Raman spectroscopy. For the first time, anharmonicity is considered explicitly in calculating the vibrational spectra of an ensemble consisting of the PYP chromophore surrounded by model compounds used as mimics of the important active-site residues. Predictions of vibrational frequencies on an ab initio corrected semiempirical potential energy surface show remarkable agreement with experimental frequencies for all three states, thus shedding light on the potential along the reaction path. For example, calculated frequencies for vibrational modes of the red-shifted intermediate, PYPL, exhibit an overall average error of 0.82% from experiment. Upon analysis of anharmonicity patterns in the PYP modes we observe a decrease in anharmonicity in the C8-C9 stretching mode nu29 (trans-cis isomerization marker mode) with the onset of the cis configuration in PYPL. This can be attributed to the loss of the hydrogen-bonding character of the adjacent C9-O2 to the methylamine (Cys69 backbone). For several of the modes, the anharmonicity is mostly due to mode-mode coupling, while for others it is mostly intrinsic. This study shows the importance of the inclusion of anharmonicity in theoretical spectroscopic calculations, and the sensitivity of experiments to anharmonicity. The characterization of protein active-site residues by small molecular mimics provides an acceptable chemical structural representation for biomolecular spectroscopy calculations. PMID:17378558

  10. Molecular structure and vibrational spectra of dithionite ion by ab initio calculations

    NASA Astrophysics Data System (ADS)

    Leszczynski, Jerzy; Zerner, Michael C.

    1989-07-01

    The structure of the dithionite ion, S 2O 42-, is examined using quantum chemical calculations. These studies strongly suggest that only the C 2h (trans) isomer is stable in solution. The C 2v (cis) form reported in Na 2S 2O 4·2H 2O is stabilized by crystal forces. The calculated vibrational spectrum of the C 2h form is in excellent agreement with that observed in aqueous solution. Taking into account the negative frequency calculated for the C 2v structure yields a calculated spectrum in good agreement with that observed for the crystal.

  11. Theoretical calculation and vibrational spectral analysis of L-arginine trifluoroacetate

    NASA Astrophysics Data System (ADS)

    Sun, Z. H.; Zhang, L.; Xu, D.; Wang, X. Q.; Liu, X. J.; Zhang, G. H.

    2008-11-01

    Fourier transform infrared and Raman spectra of the nonlinear optical crystal, L-arginine trifluoroacetate ( L-arginine·CF 3COOH, abbreviated as LATF) have been calculated by the first-principles calculation and investigated in experiment. The calculated results are slightly different from those experimental values because of the distinction resulted from the intermolecular hydrogen bonds. The role of this type of intermolecular interaction on the crystal vibrational spectra and nonlinear optical properties has been discussed. The absorption-edge on the IR side has been estimated by the theoretical approach on basis of the calculated infrared spectrum, which will be meaningful for further research on NLO crystal.

  12. Vibrational spectra, normal coordinate calculations, and molecular mechanics calculations for 3-methyl-1-hexyne and 5-methyl-1-hexyne

    NASA Astrophysics Data System (ADS)

    Crowder, G. A.; Edwards, Mary

    1994-05-01

    IR and Raman spectra were obtained for 3-methyl-1-hexyne and 5-methyl-1-hexyne. The spectra were interpreted with the aid of normal coordinate calculations. Molecular mechanics calculations were made for all possible conformers of each compound. 3-Methyl-1-hexyne existed mainly in one stable conformation (C7?C3?C4?C5?C6 coplanar), but smaller amounts of several other conformers were present. 5-Methyl-1-hexyne existed mainly as two conformers, but smaller amounts of three others were probably present. Vibrational assignments, force constants, and MM2 structural parameters are given.

  13. Quantum scattering calculations for ro-vibrational de-excitation of CO by hydrogen atoms.

    PubMed

    Song, Lei; Balakrishnan, N; van der Avoird, Ad; Karman, Tijs; Groenenboom, Gerrit C

    2015-05-28

    We present quantum-mechanical scattering calculations for ro-vibrational relaxation of carbon monoxide (CO) in collision with hydrogen atoms. Collisional cross sections of CO ro-vibrational transitions from v = 1, j = 0 - 30 to v' = 0, j' are calculated using the close coupling method for collision energies between 0.1 and 15?000 cm(-1) based on the three-dimensional potential energy surface of Song et al. [J. Phys. Chem. A 117, 7571 (2013)]. Cross sections of transitions from v = 1, j ? 3 to v' = 0, j' are reported for the first time at this level of theory. Also calculations by the more approximate coupled states and infinite order sudden (IOS) methods are performed in order to test the applicability of these methods to H-CO ro-vibrational inelastic scattering. Vibrational de-excitation rate coefficients of CO (v = 1) are presented for the temperature range from 100 K to 3000 K and are compared with the available experimental and theoretical data. All of these results and additional rate coefficients reported in a forthcoming paper are important for including the effects of H-CO collisions in astrophysical models. PMID:26026443

  14. Quantum scattering calculations for ro-vibrational de-excitation of CO by hydrogen atoms

    NASA Astrophysics Data System (ADS)

    Song, Lei; Balakrishnan, N.; van der Avoird, Ad; Karman, Tijs; Groenenboom, Gerrit C.

    2015-05-01

    We present quantum-mechanical scattering calculations for ro-vibrational relaxation of carbon monoxide (CO) in collision with hydrogen atoms. Collisional cross sections of CO ro-vibrational transitions from v = 1, j = 0 - 30 to v' = 0, j' are calculated using the close coupling method for collision energies between 0.1 and 15 000 cm-1 based on the three-dimensional potential energy surface of Song et al. [J. Phys. Chem. A 117, 7571 (2013)]. Cross sections of transitions from v = 1, j ? 3 to v' = 0, j' are reported for the first time at this level of theory. Also calculations by the more approximate coupled states and infinite order sudden (IOS) methods are performed in order to test the applicability of these methods to H-CO ro-vibrational inelastic scattering. Vibrational de-excitation rate coefficients of CO (v = 1) are presented for the temperature range from 100 K to 3000 K and are compared with the available experimental and theoretical data. All of these results and additional rate coefficients reported in a forthcoming paper are important for including the effects of H-CO collisions in astrophysical models.

  15. Floquet calculation of harmonic generation from hydrogen molecular ions in strong monochromatic laser fields

    NASA Astrophysics Data System (ADS)

    Tsogbayar, Ts; Horbatsch, M.

    2014-06-01

    We present Floquet calculations of high harmonic generation (HHG) for the lowest two electronic states of the {H}_2^+ ion by strong continuous-wave laser fields. We solve the non-Hermitian matrix problem to get accurate solutions to the periodic time-dependent Schrödinger equation (TDSE) by applying a pseudospectral representation combined with a complex absorbing potential method. This represents an alternative approach to direct TDSE solutions to obtain the harmonic spectra for the ion. We compare our HHG rates for the lower and upper states of {H}^{+}_{2}, which correspond to the gerade and ungerade ground states in the field-free case, with previously obtained results in the literature. We show that the enhancement of the ionization rates at the critical internuclear separation Rc ? 8?au plays some role in the appearance of very strong harmonic orders n = 5-11 at ? = 1064?nm and n = 5-9 at ? = 800?nm and intensity I = 1014?W?cm-2.

  16. Synthesis, crystal structure, vibrational spectra and theoretical calculation of 1-carboxymethyl-3-methylimidazolium chloride.

    PubMed

    Xuan, Xiaopeng; Wang, Na; Xue, Zaikun

    2012-10-01

    In this paper, the structure of 1-carboxymethyl-3-methylimidazolium chloride was studied by X-ray diffraction, density functional theory, and FT-IR and Raman spectroscopic techniques for the first time. Title compound crystallizes in the orthorhombic space group Pca2(1) with the cell dimensions a=13.445 (6) Å, b=6.382 (3) Å, c=9.727 (5) Å and V=834.6 (7) Å(3). All the geometrical parameters have been calculated using by B3LYP with 6-311G++(d,p) basis set. Optimized geometries have been compared with the experimental data, and the hydrogen bond and short contact interactions were discussed. The vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were calculated at the same level. The observed bands were assigned based on the theoretical calculations. The scaled vibrational frequencies seem to coincide with the experimental data with acceptable deviations. PMID:22728234

  17. Theory of high harmonic generation for probing time-resolved large-amplitude molecular vibrations with ultrashort intense lasers.

    PubMed

    Le, Anh-Thu; Morishita, T; Lucchese, R R; Lin, C D

    2012-11-16

    We present a theory that incorporates the vibrational degrees of freedom in a high-order harmonic generation (HHG) process with ultrashort intense laser pulses. In this model, laser-induced time-dependent transition dipoles for each fixed molecular geometry are added coherently, weighted by the laser-driven time-dependent nuclear wave packet distribution. We show that the nuclear distribution can be strongly modified by the HHG driving laser. The validity of this model is first checked against results from the numerical solution of the time-dependent Schrödinger equation for a simple model system. We show that in combination with the established quantitative rescattering theory this model is able to reproduce the time-resolved pump-probe HHG spectra of N(2)O(4) reported by Li et al. [Science 322, 1207 (2008)]. PMID:23215483

  18. Dynamic (hyper)polarizabilities of the sulphur dioxide molecule: coupled cluster calculations including vibrational corrections.

    PubMed

    Naves, Emílio S; Castro, Marcos A; Fonseca, Tertius L

    2012-01-01

    In this work we report results for dynamical (hyper)polarizabilities of the sulphur dioxide molecule with inclusion of vibrational corrections. The electronic contributions were computed analytically at the single and double coupled cluster level through response theories for the frequencies 0, 0.0239, 0.0428, 0.0656, 0.0720, and 0.0886 hartree. Contributions of the connected triple excitations to the dynamic electronic properties were also estimated through the multiplicative correction scheme. Vibrational corrections were calculated by means of the perturbation theoretical method. The results obtained show that the zero point vibrational correction is very small for all properties studied while the pure vibrational correction is relevant for the dc-Pockels effect, intensity dependent refractive index, and dc-Kerr effect. For these nonlinear optical processes, the pure vibrational corrections represent approximately 75%, 13%, and 6% of the corresponding electronic contributions for the higher frequencies quoted. The results presented for the polarizability are in good agreement with experimental values available in the literature. For the hyperpolarizabilities we have not obtained experimental results with precision sufficient for comparison. PMID:22239777

  19. Acoustic method for calibration of audiometric bone vibrators. II. Harmonic distortion

    E-print Network

    Allen, Jont

    measurement of inner-ear hearing sen- sitivity. Since bone vibrators are placed on the mastoid or forehead the Bruel & Kjaer type 4930 arti- ficial mastoid. The artificial mastoid converts the mechanical signal meter, oscilloscope, or sound level meter. The B&K type 4930 artificial mastoid is the only commercially

  20. Testing a simple control law to reduce broadband frequency harmonic vibrations using semi-active tuned mass dampers

    NASA Astrophysics Data System (ADS)

    Moutinho, Carlos

    2015-05-01

    This paper is focused on the control problems related to semi-active tuned mass dampers (TMDs) used to reduce harmonic vibrations, specially involving civil structures. A simplified version of the phase control law is derived and its effectiveness is investigated and evaluated. The objective is to improve the functioning of control systems of this type by simplifying the measurement process and reducing the number of variables involved, making the control system more feasible and reliable. Because the control law is of ON/OFF type, combined with appropriate trigger conditions, the activity of the actuation system may be significantly reduced, which may be of few seconds a day in many practical cases, increasing the durability of the device and reducing its maintenance. Moreover, due to the ability of the control system to command the motion of the inertial mass, the semi-active TMD is relatively insensitive to its initial tuning, resulting in the capability of self-tuning and in the possibility of controlling several vibration modes of a structure over a significant broadband frequency.

  1. Motion of a condensate in a shaken and vibrating harmonic trap

    E-print Network

    Y. Japha; Y. B. Band

    2002-04-14

    The dynamics of a Bose-Einstein condensate (BEC) in a time-dependent harmonic trapping potential is determined for arbitrary variations of the position of the center of the trap and its frequencies. The dynamics of the BEC wavepacket is soliton-like. The motion of the center of the wavepacket, and the spatially and temporally dependent phase (which affects the coherence properties of the BEC) multiplying the soliton-like part of the wavepacket, are analytically determined.

  2. Efficient calculation of inelastic vibration signals in electron transport: Beyond the wide-band approximation

    NASA Astrophysics Data System (ADS)

    Lü, Jing-Tao; Christensen, Rasmus B.; Foti, Giuseppe; Frederiksen, Thomas; Gunst, Tue; Brandbyge, Mads

    2014-02-01

    We extend the simple and efficient lowest order expansion (LOE) for inelastic electron tunneling spectroscopy (IETS) to include variations in the electronic structure on the scale of the vibration energies. This enables first-principles calculations of IETS line shapes for molecular junctions close to resonances and band edges. We demonstrate how this is relevant for the interpretation of experimental IETS using both a simple model and first-principles simulations.

  3. Optimal configuration for vibration frequencies in a ring of harmonic oscillators: The nonidentical mass effect

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Zhang, Guo-Yong; He, Zhiwei; Zhan, Meng

    2015-06-01

    The parameter diversity effect in coupled nonidentical elements has attracted persistent interest in nonlinear dynamics. Of fundamental importance is the so-called optimal configuration problem for how the spatial position of elements with different parameters precisely determines the dynamics of the whole system. In this work, we study the optimal configuration problem for the vibration spectra in the classical mass-spring model with a ring configuration, paying particular attention to how the configuration of different masses affects the second smallest vibration frequency ( ? 2) and the largest one ( ? N ). For the extreme values of ? 2 and ? N , namely, ( ? 2)min, ( ? 2)max, ( ? N )min, and ( ? N )max, we find some explicit organization rules for the optimal configurations and some approximation rules when the explicit organization rules are not available. The different distributions of ? 2 and ? N are compared. These findings are interesting and valuable for uncovering the underlying mechanism of the parameter diversity effect in more general cases.

  4. Mapping quadrupole collectivity in the Cd isotopes: The breakdown of harmonic vibrational motion

    Microsoft Academic Search

    P. E. Garrett; K. L. Green; J. Bangay; A. Diaz Varela; C. S. Sumithrarachchi; R. A. E. Austin; G. C. Ball; D. S. Bandyopadhyay; L. Bianco; S. Colosimo; D. S. Cross; G. A. Demand; P. Finlay; A. B. Garnsworthy; G. F. Grinyer; G. Hackman; W. D. Kulp; K. G. Leach; A. C. Morton; J. N. Orce; C. J. Pearson; A. A. Phillips; M. A. Schumaker; C. E. Svensson; S. Triambak; J. Wong; J. L. Wood; S. W. Yates

    2011-01-01

    The stable Cd isotopes have long been used as paradigms for spherical vibrational motion. Extensive investigations with in-beam ? spectroscopy have resulted in very-well-established level schemes, including many lifetimes or lifetime limits. A programme has been initiated to complement these studies with very-high-statistics ? decay using the 8? spectrometer at the TRIUMF radioactive beam facility. The decays of 112In and

  5. Accurate quantum dynamics calculations of vibrational spectrum of dideuteromethane CH2D2

    NASA Astrophysics Data System (ADS)

    Yu, Hua-Gen

    2015-05-01

    We report a rigorous variational study of the infrared (IR) vibrational spectra of both CH2D2 and 13CH2D2 isotopomers using an exact molecular Hamiltonian. Calculations are carried out using a recently developed multi-layer Lanczos algorithm based on the accurate refined Wang and Carrington potential energy surface of methane and the low-order truncated ab initio dipole moment surface of Yurchenko et al. [J. Mol. Spectrosc. 291, 69 (2013)]. All well converged 357 vibrational energy levels up to 6100 cm-1 of CH2D2 are obtained, together with a comparison to previous calculations and 91 experimental bands available. The calculated frequencies are in excellent agreement with the experimental results and give a root-mean-square error of 0.67 cm-1. In particular, we also compute the transition intensities from the vibrational ground state for both isotopomers. Based on the theoretical results, 20 experimental bands are suggested to be re-assigned. Surprisingly, an anomalous C isotopic effect is discovered in the n?5 modes of CH2D2. The predicted IR spectra provide useful information for understanding those unknown bands.

  6. Accurate quantum dynamics calculations of vibrational spectrum of dideuteromethane CH2D2.

    PubMed

    Yu, Hua-Gen

    2015-05-21

    We report a rigorous variational study of the infrared (IR) vibrational spectra of both CH2D2 and (13)CH2D2 isotopomers using an exact molecular Hamiltonian. Calculations are carried out using a recently developed multi-layer Lanczos algorithm based on the accurate refined Wang and Carrington potential energy surface of methane and the low-order truncated ab initio dipole moment surface of Yurchenko et al. [J. Mol. Spectrosc. 291, 69 (2013)]. All well converged 357 vibrational energy levels up to 6100 cm(-1) of CH2D2 are obtained, together with a comparison to previous calculations and 91 experimental bands available. The calculated frequencies are in excellent agreement with the experimental results and give a root-mean-square error of 0.67?cm(-1). In particular, we also compute the transition intensities from the vibrational ground state for both isotopomers. Based on the theoretical results, 20 experimental bands are suggested to be re-assigned. Surprisingly, an anomalous C isotopic effect is discovered in the n?5 modes of CH2D2. The predicted IR spectra provide useful information for understanding those unknown bands. PMID:26001461

  7. Molecular structure, vibrational, electronic and thermal properties of 4-vinylcyclohexene by quantum chemical calculations.

    PubMed

    Nagabalasubramanian, P B; Periandy, S; Karabacak, Mehmet; Govindarajan, M

    2015-06-15

    The solid phase FT-IR and FT-Raman spectra of 4-vinylcyclohexene (abbreviated as 4-VCH) have been recorded in the region 4000-100cm(-1). The optimized molecular geometry and vibrational frequencies of the fundamental modes of 4-VCH have been precisely assigned and analyzed with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method at 6-311++G(d,p) level basis set. The theoretical frequencies were properly scaled and compared with experimentally obtained FT-IR and FT-Raman spectra. Also, the effect due the substitution of vinyl group on the ring vibrational frequencies was analyzed and a detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated total energy distribution (TED). The time dependent DFT (TD-DFT) method was employed to predict its electronic properties, such as electronic transitions by UV-Visible analysis, HOMO and LUMO energies, molecular electrostatic potential (MEP) and various global reactivity and selectivity descriptors (chemical hardness, chemical potential, softness, electrophilicity index). Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Atomic charges obtained by Mulliken population analysis and NBO analysis are compared. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures are also calculated. PMID:25795608

  8. Molecular structure, vibrational, electronic and thermal properties of 4-vinylcyclohexene by quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Nagabalasubramanian, P. B.; Periandy, S.; Karabacak, Mehmet; Govindarajan, M.

    2015-06-01

    The solid phase FT-IR and FT-Raman spectra of 4-vinylcyclohexene (abbreviated as 4-VCH) have been recorded in the region 4000-100 cm-1. The optimized molecular geometry and vibrational frequencies of the fundamental modes of 4-VCH have been precisely assigned and analyzed with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method at 6-311++G(d,p) level basis set. The theoretical frequencies were properly scaled and compared with experimentally obtained FT-IR and FT-Raman spectra. Also, the effect due the substitution of vinyl group on the ring vibrational frequencies was analyzed and a detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated total energy distribution (TED). The time dependent DFT (TD-DFT) method was employed to predict its electronic properties, such as electronic transitions by UV-Visible analysis, HOMO and LUMO energies, molecular electrostatic potential (MEP) and various global reactivity and selectivity descriptors (chemical hardness, chemical potential, softness, electrophilicity index). Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Atomic charges obtained by Mulliken population analysis and NBO analysis are compared. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures are also calculated.

  9. Full dimensional Franck-Condon factors for the acetylene tilde{{A}} 1Au—{tilde{X}} {^1? _g^+} transition. I. Method for calculating polyatomic linear—bent vibrational intensity factors and evaluation of calculated intensities for the gerade vibrational modes in acetylene

    NASA Astrophysics Data System (ADS)

    Park, G. Barratt

    2014-10-01

    Franck-Condon vibrational overlap integrals for the tilde{A} {^1A_u}—{tilde{X}} {^1? _g^+} transition in acetylene have been calculated in full dimension in the harmonic normal mode basis. The calculation uses the method of generating functions first developed for polyatomic Franck-Condon factors by Sharp and Rosenstock [J. Chem. Phys. 41(11), 3453-3463 (1964)], and previously applied to acetylene by Watson [J. Mol. Spectrosc. 207(2), 276-284 (2001)] in a reduced-dimension calculation. Because the transition involves a large change in the equilibrium geometry of the electronic states, two different types of corrections to the coordinate transformation are considered to first order: corrections for axis-switching between the Cartesian molecular frames and corrections for the curvilinear nature of the normal modes at large amplitude. The angular factor in the wavefunction for the out-of-plane component of the trans bending mode, ? _4^' ' }, is treated as a rotation, which results in an Eckart constraint on the polar coordinates of the bending modes. To simplify the calculation, the other degenerate bending mode, ? _5^' ' }, is integrated in the Cartesian basis and later transformed to the constrained polar coordinate basis, restoring the conventional v and l quantum numbers. An updated tilde{A}-state harmonic force field obtained recently in the R. W. Field research group is evaluated. The results for transitions involving the gerade vibrational modes are in qualitative agreement with experiment. Calculated results for transitions involving ungerade modes are presented in Paper II of this series [G. B. Park, J. H. Baraban, and R. W. Field, "Full dimensional Franck-Condon factors for the acetylene tilde{A} {^1A_u}—{tilde{X}} {^1? _g^+} transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes," J. Chem. Phys. 141, 134305 (2014)].

  10. Full dimensional Franck-Condon factors for the acetylene A? (1)A(u)-X? (1)?(g)(+) transition. I. Method for calculating polyatomic linear-bent vibrational intensity factors and evaluation of calculated intensities for the gerade vibrational modes in acetylene.

    PubMed

    Park, G Barratt

    2014-10-01

    Franck-Condon vibrational overlap integrals for the A? Au1-X? 1?g+ transition in acetylene have been calculated in full dimension in the harmonic normal mode basis. The calculation uses the method of generating functions first developed for polyatomic Franck-Condon factors by Sharp and Rosenstock [J. Chem. Phys. 41(11), 3453-3463 (1964)], and previously applied to acetylene by Watson [J. Mol. Spectrosc. 207(2), 276-284 (2001)] in a reduced-dimension calculation. Because the transition involves a large change in the equilibrium geometry of the electronic states, two different types of corrections to the coordinate transformation are considered to first order: corrections for axis-switching between the Cartesian molecular frames and corrections for the curvilinear nature of the normal modes at large amplitude. The angular factor in the wavefunction for the out-of-plane component of the trans bending mode, ?4(?), is treated as a rotation, which results in an Eckart constraint on the polar coordinates of the bending modes. To simplify the calculation, the other degenerate bending mode, ?5(?), is integrated in the Cartesian basis and later transformed to the constrained polar coordinate basis, restoring the conventional v and l quantum numbers. An updated A?-state harmonic force field obtained recently in the R. W. Field research group is evaluated. The results for transitions involving the gerade vibrational modes are in qualitative agreement with experiment. Calculated results for transitions involving ungerade modes are presented in Paper II of this series [G. B. Park, J. H. Baraban, and R. W. Field, "Full dimensional Franck-Condon factors for the acetylene A? Au1-X? 1?g+ transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes," J. Chem. Phys. 141, 134305 (2014)]. PMID:25296803

  11. Vibrational calculations and potential determination for ArOH* ( v=0, 1) and ArOD* ( v=0, 1)

    NASA Astrophysics Data System (ADS)

    Schnupf, Udo; Bowman, Joel M.; Heaven, Michael C.

    1992-02-01

    We present calculated vibrational energy intervals for ArOH(D) ( 2? +, v=0 and 1) based on exact vibrational calculations for total angular momentum exclusive of electron spin, N=0 and a centrifugal sudden approximation for N=1. A modification of a previous potential surface for the v=0 complex (J.M. Bowman, B. Gazdy, P. Schafer and M.C. Heaven) is made to include explicit OH(D) vibrational dependence. By a trial-and-error procedure the potential parameters are optimized to give good agreement with experiment for the vibrational energy intervals. Rotation constants are also calculated and are in good agreement with experiment. Vibrational wavefunctions are presented which serve to explain an interesting inverse isotope effect in the van der Waals stretching intervals.

  12. Comparative vibrational spectroscopic studies, HOMO-LUMO, NBO analyses and thermodynamic functions of p-cresol and 2-methyl-p-cresol based on DFT calculations.

    PubMed

    Balachandran, V; Murugan, M; Nataraj, A; Karnan, M; Ilango, G

    2014-11-11

    In the present study structural properties of p-cresol, and 2-methoxy-p-cresol have been studied by using B3LYP/cc-pvdz and B3PW91/cc-pvdz of Density Functional Theory (DFT) utilizing Becke three exchange functional and Lee Yang Paar correlation functional. The Fourier transform infrared and Fourier transform Raman spectra of title molecules were recorded (solid phase). Optimized geometry, harmonic vibrational frequencies and various thermodynamic parameters of the title compounds were calculated with B3LYP/cc-pvdz, and B3PW91/cc-pvdz basis sets. Non-linear optical (NLO) behavior of the p-cresol and 2-methoxy-p-cresol were investigated by determining of electric dipole moment, polarizability ?, and hyperpolarizability ? using the above mentioned basis sets. The molecular properties such as ionization potential, electronegativity, chemical potential, electrophilicity have been deduced from HOMO-LUMO analysis employing the same basis sets. A detailed interpretation of the infrared and Raman spectra of title molecules were reported. UV spectrum was measured in different solvent. The energy and oscillator strength are calculated by Time Dependant Density Functional Theory (TD-DFT) results. The calculated HOMO and LUMO energies also confirm that charge transfer occurs within the molecule. The complete assignments were performed on the basis of the potential energy distribution (PED) of vibrational modes, calculated with scaled quantum mechanics (SQM) method. Finally the theoretical FT-IR, FT-Raman, and UV spectra of the title molecules have also been constructed. PMID:24892532

  13. Conformational stability, vibrational spectra, molecular structure, NBO and HOMO-LUMO analysis of 5-nitro-2-furaldehyde oxime based on DFT calculations

    NASA Astrophysics Data System (ADS)

    Arivazhagan, M.; Jeyavijayan, S.; Geethapriya, J.

    2013-03-01

    The FTIR and FT-Raman spectra of 5-nitro-2-furaldehyde oxime (NFAO) have been recorded in the regions 4000-400 cm-1 and 3500-50 cm-1, respectively. The total energies of different conformations have been obtained from DFT (B3LYP) with 6-311++G(d,p) basis set calculations. The computational results identify the most stable conformer of NFAO as the C1 form. Utilizing the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by density functional theory (DFT/B3LYP) method with 6-31+G(d,p) and 6-311++G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of NFAO is also reported based on total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. Besides, molecular electrostatic potential (MEP), HOMO and LUMO analysis, and several thermodynamic properties were performed by the DFT method. Mulliken's net charges have been calculated and compared with the natural atomic charges. Ultraviolet-visible spectrum of the title molecule has also been calculated using TD-DFT method.

  14. A refined quartic potential energy surface and large scale vibrational calculations for S0 thiophosgene.

    PubMed

    Rashev, Svetoslav; Moule, David C

    2015-04-01

    In this work we present a full 6D quartic potential energy surface (PES) for S0 thiophosgene in curvilinear symmetrized bond-angle coordinates. The PES was refined starting from an ab initio field derived from acc-pVTZ basis set with CCSD(T) corrections for electron correlation. In the present calculations we used our variational method that was recently tested on formaldehyde and some of its isotopomers, along with additional improvements. The lower experimentally known vibrational levels for 35Cl2CS were reproduced quite well in the calculations, which can be regarded as a test for the feasibility of the obtained quartic PES. PMID:25615683

  15. A refined quartic potential energy surface and large scale vibrational calculations for S0 thiophosgene

    NASA Astrophysics Data System (ADS)

    Rashev, Svetoslav; Moule, David C.

    2015-04-01

    In this work we present a full 6D quartic potential energy surface (PES) for S0 thiophosgene in curvilinear symmetrized bond-angle coordinates. The PES was refined starting from an ab initio field derived from acc-pVTZ basis set with CCSD(T) corrections for electron correlation. In the present calculations we used our variational method that was recently tested on formaldehyde and some of its isotopomers, along with additional improvements. The lower experimentally known vibrational levels for 35Cl2CS were reproduced quite well in the calculations, which can be regarded as a test for the feasibility of the obtained quartic PES.

  16. Development and applications of algorithms for calculating the transonic flow about harmonically oscillating wings

    NASA Technical Reports Server (NTRS)

    Ehlers, F. E.; Weatherill, W. H.; Yip, E. L.

    1984-01-01

    A finite difference method to solve the unsteady transonic flow about harmonically oscillating wings was investigated. The procedure is based on separating the velocity potential into steady and unsteady parts and linearizing the resulting unsteady differential equation for small disturbances. The differential equation for the unsteady velocity potential is linear with spatially varying coefficients and with the time variable eliminated by assuming harmonic motion. An alternating direction implicit procedure was investigated, and a pilot program was developed for both two and three dimensional wings. This program provides a relatively efficient relaxation solution without previously encountered solution instability problems. Pressure distributions for two rectangular wings are calculated. Conjugate gradient techniques were developed for the asymmetric, indefinite problem. The conjugate gradient procedure is evaluated for applications to the unsteady transonic problem. Different equations for the alternating direction procedure are derived using a coordinate transformation for swept and tapered wing planforms. Pressure distributions for swept, untaped wings of vanishing thickness are correlated with linear results for sweep angles up to 45 degrees.

  17. Active vibration control of a ring-stiffened cylindrical shell in contact with unbounded external fluid and subjected to harmonic disturbance by piezoelectric sensor and actuator

    NASA Astrophysics Data System (ADS)

    Kwak, Moon K.; Yang, Dong-Ho

    2013-09-01

    This paper is concerned with the suppression of vibrations and radiated sound of a ring-stiffened circular cylindrical shell in contact with unbounded external fluid by means of piezoelectric sensors and actuators. The dynamic model of a circular cylindrical shell based on the Sanders shell theory was considered together with a ring stiffener model. The mass and stiffness matrices for a ring stiffener were newly derived in this study and added to the mass and stiffness matrices of the cylindrical shell, respectively. The fluid-added mass matrix, which was derived by using the baffled shell theory, was also added to the mass matrix. Finally, the equations representing the piezoelectric sensor measurement and piezoelectric actuation complete the theoretical model for the addressed problem. The natural vibration characteristics of the ring-stiffened cylindrical shell both in air and in water were investigated both theoretically and experimentally. The theoretical predictions were in good agreement with the experimental results. An active vibration controller which can cope with a harmonic disturbance was designed by considering the modified higher harmonic control, which is, in fact, a band rejection filter. An active vibration control experiment on the submerged cylindrical shell was carried out in a water tank and the digital control system was used. The experimental results showed that both vibrations and radiation sound of the submerged cylindrical shell were suppressed by a pair of piezoelectric sensor and actuator.

  18. Finite Element Analysis of Forced Vibration for a Pipe Conveying Harmonically Pulsating Fluid

    NASA Astrophysics Data System (ADS)

    Seo, Young Soo; Jeong, Weui Bong; Jeong, Seok Hyeon; Oh, Jun Suk; Yoo, Wan Suk

    It is well known that the natural frequencies of a pipe become lower as uniform internal fluid velocity increases. The pipe becomes unstable if the fluid is faster than the critical velocity. But in the case of a pipe conveying harmonically pulsating fluid, resonances will occur even though the mean velocity of the fluid is below the critical velocity. Therefore, for improved analysis, the effects of pulsating fluid in the pipe should also be taken into consideration. In this study, a finite element formulation for the pipe was carried out while taking into consideration the effects of the fluid pulsating harmonically in the pipe. The damping and stiffness matrices in the finite element equation vary with time. A stability analysis based on the Bolotin method was carried out. And, a method to directly estimate the forced response of the pipe that does not need to solve a time data from time-variant system is presented. Several numerical examples are given in this paper that validate of this method.

  19. Vibrational spectra, structural conformations, scaled quantum chemical calculations and NBO analysis of 3-acetyl-7-methoxycoumarin

    NASA Astrophysics Data System (ADS)

    Joseph, Lynnette; Sajan, D.; Reshmy, R.; Arun Sasi, B. S.; Erdogdu, Y.; Thomas, K. Kurien

    2012-12-01

    The powder form NIR-FT Raman and FT-IR spectra of 3-acetyl-7-methoxycoumarin (3A7MC) have been recorded in the regions 4000-400 and 3500-100 cm-1, respectively. The equilibrium geometry, vibrational frequencies, band intensities, NMR spectra, NBO analysis and UV-Vis spectral studies of the most stable conformer have been calculated by density functional B3LYP method with the 6-311G(d,p) basis set. A complete vibrational analysis has been attempted on the basis of experimental infrared and Raman spectra, the calculated wavenumber and intensity of the vibrational bands and the potential energy distribution over the internal coordinates. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping the electron density isosurface with electrostatic potential surfaces (ESP). Natural bond orbital analysis has been carried out to understand the nature of different interactions responsible for the electron delocalization and the intramolecular charge transfer between the orbitals (n ? ??, n ? ??, ? ? ??).

  20. Calculations of the infrared and vibrational circular dichroism spectra of ethanol and its deuterated isotopomers

    SciTech Connect

    Dothe, H.; Lowe, M.A. (Boston Univ., MA (USA)); Alper, J.S. (Univ. of Massachusetts, Boston (USA))

    1989-09-07

    The scaled quantum mechanical force field method together with the Stephens formalism for the evaluation of rotational strengths has been used to calculate infrared and vibrational circular dichroism (VCD) spectra of ethanol and its deuterated isotopomers. For the IR spectra, agreement between the calculated and experimental spectra is extremely good; the root-mean-square deviation between the calculated and experimental frequencies for all 12 isotopomers is 15 cm{sup {minus}1}. The calculated VCD spectra are also in good agreement with the experimental ones when the evaluation of the rotational strengths is carried out using the distributed origin gauge. Both the IR and VCD results confirm the earlier conjecture that the gauche conformer predominates over the trans, even though the trans has a slightly lower SCF energy.

  1. Ab initio calculations of anharmonic vibrational spectroscopy for hydrogen fluoride (HF)n (n = 3, 4) and mixed hydrogen fluoride/water (HF)n(H2O)n (n = 1, 2, 4) clusters

    NASA Technical Reports Server (NTRS)

    Chaban, Galina M.; Gerber, R. Benny

    2002-01-01

    Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n, with n = 3, 4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n = 1, 2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the Moller-Plesset (MP2) potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments.

  2. Ab Initio Calculations of Anharmonic Vibrational Spectroscopy for Hydrogen Fluoride (HF)n (n=3,4) and Mixed Hydrogen Fluoride/Water (HF)n(H20)n (n=1,2,4) Clusters

    NASA Technical Reports Server (NTRS)

    Chaban, Galina M.; Gerber, R. Benny; Kwak, Dochan (Technical Monitor)

    2001-01-01

    Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n with n=3,4 and mixed clusters of hydrogen fluoride with water (HF)n(H2O)n where n=1,2. For the (HF)4(H2O)4 complex, the vibrational spectra are calculated at the harmonic level, and anharmonic effects are estimated. Potential energy surfaces for these systems are obtained at the MP2/TZP level of electronic structure theory. Vibrational states are calculated from the potential surface points using the correlation-corrected vibrational self-consistent field (CC-VSCF) method. The method accounts for the anharmonicities and couplings between all vibrational modes and provides fairly accurate anharmonic vibrational spectra that can be directly compared with experimental results without a need for empirical scaling. For (HF)n, good agreement is found with experimental data. This agreement shows that the MP2 potential surfaces for these systems are reasonably reliable. The accuracy is best for the stiff intramolecular modes, which indicates the validity of MP2 in describing coupling between intramolecular and intermolecular degrees of freedom. For (HF)n(H2O)n experimental results are unavailable. The computed intramolecular frequencies show a strong dependence on cluster size. Intensity features are predicted for future experiments.

  3. Comparison of DFT methods for molecular structure and vibration spectra of ofloxacin calculations

    NASA Astrophysics Data System (ADS)

    Yang, Yue; Gao, Hongwei

    2012-01-01

    Comparison of the performance of different density functional theory (DFT) methods at various basis sets in predicting molecular and vibration spectra of ofloxacin was reported. The methods employed in this study comprise six functionals, namely, mPW1PW91, HCTH, LSDA, PBEPBE, B3PW91 and B3LYP. Different basis sets including LANL2DZ, SDD, LANL2MB, 6-31g, 6-311g and 3-21g were also examined. Comparison between the calculated and experimental data indicates that the mPW1PW91/6-311g level afford the best quality to predict the structure of ofloxacin. The results also indicate that B3LYP/LANL2DZ level show better performance in the vibration spectra prediction of ofloxacin than other DFT methods.

  4. Molecular structure, vibrational spectral studies of pyrazole and 3,5-dimethyl pyrazole based on density functional calculations

    NASA Astrophysics Data System (ADS)

    Krishnakumar, V.; Jayamani, N.; Mathammal, R.

    2011-09-01

    In this work, the experimental and theoretical vibrational spectra of pyrazole (PZ) and 3,5-dimethyl pyrazole (DMP) have been studied. FTIR and FT-Raman spectra of the title compounds in the solid phase are recorded in the region 4000-400 cm -1 and 4000-50 cm -1, respectively. The structural and spectroscopic data of the molecules in the ground state are calculated using density functional methods (B3LYP) with 6-311+G** basis set. The vibrational frequencies are calculated and scaled values are compared with experimental FTIR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete vibrational assignments are performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanical (SM) method. 13C and 1H NMR chemical shifts results are compared with the experimental values.

  5. RESEARCH NOTE: On the efficient calculation of ordinary and generalized spherical harmonics

    NASA Astrophysics Data System (ADS)

    Masters, Guy; Richards-Dinger, Keith

    1998-10-01

    Algorithms for the stable computation of generalized and ordinary spherical harmonics are presented. The algorithms are fast and have the useful property that they can compute harmonics for isolated harmonic degrees. fortran and C programs implementing these algorithms are available from the authors.

  6. Infrared and ultraviolet cutoffs in variational calculations with a harmonic oscillator basis

    E-print Network

    Sidney A Coon

    2013-03-26

    I abstract from a recent publication [1] the motivations for, analysis in and conclusions of a study of the ultraviolet and infrared momentum regulators induced by the necessary truncation of the model spaces formed by a variational trial wave function. This trial function is built systematically from a complete set of many-body basis states based upon three-dimensional harmonic oscillator (HO) functions. Each model space is defined by a truncation of the expansion characterized by a counting number (N) and by the intrinsic scale ($\\hbar\\omega$) of the HO basis. Extending both the uv cutoff to infinity and the ir cutoff to zero is prescribed for a converged calculation. In [1] we established practical procedures which utilize these regulators to obtain the extrapolated result from sequences of calculations with model spaces. Finally, I update this subject by mentioning recent work on our extrapolation prescriptions which have appeared since the submission of [1]. The numerical example chosen for this contribution consists of calculations of the ground state energy of the triton with the "bare" and "soft" Idaho N3LO nucleon-nucleon (NN) interaction.

  7. An exact variational method to calculate vibrational energies of five atom molecules beyond the normal mode approach

    Microsoft Academic Search

    Hua-Gen Yu

    2002-01-01

    A full dimensional variational algorithm to calculate vibrational energies of penta-atomic molecules is presented. The quantum mechanical Hamiltonian of the system for J=0 is derived in a set of orthogonal polyspherical coordinates in the body-fixed frame without any dynamical approximation. The vibrational Hamiltonian has been obtained in an explicitly Hermitian form. Variational calculations are performed in a direct product discrete

  8. A novel boundary element approach to time-harmonic dynamics of incremental nonlinear elasticity: The role of pre-stress on structural vibrations and dynamic shear banding

    Microsoft Academic Search

    D. Bigoni; D. Capuani; P. Bonetti; S. Colli

    2007-01-01

    A new boundary element technique is developed to analyze two-dimensional, time-harmonic, small-amplitude vibrations, superimposed upon a homogeneously pre-stressed, orthotropic and incompressible elastic solid. New expressions for the Green’s functions for incremental applied tractions are obtained, in which ‘static’ and ‘dynamic’ contributions are uncoupled. The dynamic contributions are regular, whereas the static terms are strongly singular and are solved in closed-form

  9. A comparison of force fields and calculation methods for vibration intervals of isotopic H3(+) molecules

    NASA Astrophysics Data System (ADS)

    Carney, G. D.; Adler-Golden, S. M.; Lesseski, D. C.

    1986-04-01

    This paper reports (1) improved values for low-lying vibration intervals of H3(+), H2D(+), D2H(+), and D3(+) calculated using the variational method and Simons-Parr-Finlan (1973) representations of the Carney-Porter (1976) and Dykstra-Swope (1979) ab initio H3(+) potential energy surfaces, (2) quartic normal coordinate force fields for isotopic H3(+) molecules, (3) comparisons of variational and second-order perturbation theory, and (4) convergence properties of the Lai-Hagstrom internal coordinate vibrational Hamiltonian. Standard deviations between experimental and ab initio fundamental vibration intervals of H3(+), H2D(+), D2H(+), and D3(+) for these potential surfaces are 6.9 (Carney-Porter) and 1.2/cm (Dykstra-Swope). The standard deviations between perturbation theory and exact variational fundamentals are 5 and 10/cm for the respective surfaces. The internal coordinate Hamiltonian is found to be less efficient than the previously employed 't' coordinate Hamiltonian for these molecules, except in the case of H2D(+).

  10. Accurate variational calculations and analysis of the HOCl vibrational energy spectrum

    SciTech Connect

    Skokov, S.; Qi, J.; Bowman, J.M. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Altanta, Georgia 30322 (United States)] [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Altanta, Georgia 30322 (United States); Yang, C.; Gray, S.K. [Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Peterson, K.A. [Department of Chemistry, Washington State University, Richland, Washington 99352 (United States)] [Department of Chemistry, Washington State University, Richland, Washington 99352 (United States); [the Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Mandelshtam, V.A. [Department of Chemistry, University of California at Irvine, Irvine, California 92697 (United States)] [Department of Chemistry, University of California at Irvine, Irvine, California 92697 (United States)

    1998-12-01

    Large scale variational calculations for the vibrational states of HOCl are performed using a recently developed, accurate {ital ab initio} potential energy surface. Three different approaches for obtaining vibrational states are employed and contrasted; a truncation/recoupling scheme with direct diagonalization, the Lanczos method, and Chebyshev iteration with filter diagonalization. The complete spectrum of bound states for nonrotating HOCl is computed and analyzed within a random matrix theory framework. This analysis indicates almost entirely regular dynamics with only a small degree of chaos. The nearly regular spectral structure allows us to make assignments for the most significant part of the spectrum, based on analysis of coordinate expectation values and eigenfunctions. Ground state dipole moments and dipole transition probabilities are also calculated using accurate {ital ab initio} data. Computed values are in good agreement with available experimental data. Some exact rovibrational calculations for J=1, including Coriolis coupling, are performed. The exact results are nearly identical with those obtained from the adiabatic rotation approximation and very close to those from the centrifugal sudden approximation, thus indicating a very small degree of asymmetry and Coriolis coupling for the HOCl molecule. {copyright} {ital 1998 American Institute of Physics.}

  11. Structural, electronic, thermodynamical and charge transfer properties of Chloramphenicol Palmitate using vibrational spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Mishra, Rashmi; Srivastava, Anubha; Sharma, Anamika; Tandon, Poonam; Baraldi, Cecilia; Gamberini, Maria Christina

    2013-01-01

    The global problem of advancing bacterial resistance to newer drugs has led to renewed interest in the use of Chloramphenicol Palmitate (C27H42Cl2N2O6) [Palmitic acid alpha ester with D-threo-(-),2-dichloro-N-(beta-hydroxy-alpha-(hydroxymethyl)-p-nitrophenethyl)acetamide also known as Detereopal]. The characterization of the three polymorphic forms of Chloramphenicol Palmitate (CPP) was done spectroscopically by employing FT-IR and FT-Raman techniques. The equilibrium geometry, various bonding features, and harmonic wavenumbers have been investigated for most stable form A with the help of DFT calculations and a good correlation was found between experimental data and theoretical values. Electronic properties have been analyzed employing TD-DFT for both gaseous and solvent phase. The theoretical calculation of thermodynamical properties along with NBO analysis has also been performed to have a deep insight into the molecule for further applications.

  12. Quantum Mechanical Calculations to Interpret Vibrational and NMR Spectra of Organic Compounds Adsorbed onto Mineral Surfaces

    NASA Astrophysics Data System (ADS)

    Kubicki, J. D.

    2008-12-01

    Vibrational (e.g., ATR FTIR and Raman) and nuclear magnetic resonance (NMR) spectroscopies provide excellent information on the bonding and atomic environment of adsorbed organic compounds. However, interpretation of observed spectra collected for organic compounds adsorbed onto mineral surfaces can be complicated by the lack of comparable analogs of known structure and uncertainties about the mineral surface structure. Quantum mechanical calculations provide a method for testing interpretations of observed spectra because models can be built to mimic predicted structures, and the results are independent of experimental parameters (i.e., no fitting to data is necessary). In this talk, methodologies for modeling vibrational frequencies and NMR chemical shifts of adsorbed organic compounds are discussed. Examples included salicylic acid (as an analog for important binding functional groups in humic acids) adsorbed onto aluminum oxides, organic phosphoryl compounds that represent herbicides and bacterial extracellular polymeric substances (EPS), and ofloxacin (a common agricultural antibiotic). The combination of the ability of quantum mechanical calculations to predict structures, spectroscopic parameters and energetics of adsorption with experimental data on these same properties allows for more definitive construction of surface complex models.

  13. Structural, vibrational, NLO, MEP, NBO analysis and DFT calculation of bis 2,5-dimethylanilinium sulfate

    NASA Astrophysics Data System (ADS)

    Guidara, Sameh; Feki, Habib; Abid, Younes

    2015-01-01

    A new organic-inorganic salt, bis 2,5-dimethylanilinium sulfate has been synthesized by slow evaporation method at room temperature and characterized by single X-ray diffraction, FT-IR and FT-Raman spectroscopies. The optimized molecular structure, vibrational wavenumbers, atomic charges, molecular electrostatic potential, NBO, NLO and electronic properties were calculated by the density functional theory (DFT) method using the B3LYP function with the 6-31G(d,p) basis set. The complete assignments of the vibrational spectra were carried out with the aid of potential energy distribution (PED). Simulation of infrared and Raman spectra led to excellent overall agreement with the observed spectral patterns. The stability and charge delocalization of the molecule were studied by natural bond orbital (NBO) analysis. In addition, a molecular electrostatic potential map (MEP) of the title compound has been analyzed for predicting the reactive sites. NLO properties and Mulliken charges were also calculated and interpreted. The lowering in the HOMO and LUMO energy gap explains the eventual charge transfer interactions that take place within the molecules.

  14. Vibrational spectra of light and heavy water with application to neutron cross section calculations.

    PubMed

    Marquez Damian, J I; Malaspina, D C; Granada, J R

    2013-07-14

    The design of nuclear reactors and neutron moderators require a good representation of the interaction of low energy (E < 1 eV) neutrons with hydrogen and deuterium containing materials. These models are based on the dynamics of the material, represented by its vibrational spectrum. In this paper, we show calculations of the frequency spectrum for light and heavy water at room temperature using two flexible point charge potentials: SPC-MPG and TIP4P/2005f. The results are compared with experimental measurements, with emphasis on inelastic neutron scattering data. Finally, the resulting spectra are applied to calculation of neutron scattering cross sections for these materials, which were found to be a significant improvement over library data. PMID:23862950

  15. Improved methods for Feynman path integral calculations of vibrational-rotational free energies and application to isotopic fractionation of hydrated chloride ions.

    PubMed

    Mielke, Steven L; Truhlar, Donald G

    2009-04-23

    We present two enhancements to our methods for calculating vibrational-rotational free energies by Feynman path integrals, namely, a sequential sectioning scheme for efficiently generating random free-particle paths and a stratified sampling scheme that uses the energy of the path centroids. These improved methods are used with three interaction potentials to calculate equilibrium constants for the fractionation behavior of Cl(-) hydration in the presence of a gas-phase mixture of H(2)O, D(2)O, and HDO. Ion cyclotron resonance experiments indicate that the equilibrium constant, K(eq), for the reaction Cl(H(2)O)(-) + D(2)O right harpoon over left harpoon Cl(D(2)O)(-) + H(2)O is 0.76, whereas the three theoretical predictions are 0.946, 0.979, and 1.20. Similarly, the experimental K(eq) for the Cl(H(2)O)(-) + HDO right harpoon over left harpoon Cl(HDO)(-) + H(2)O reaction is 0.64 as compared to theoretical values of 0.972, 0.998, and 1.10. Although Cl(H(2)O)(-) has a large degree of anharmonicity, K(eq) values calculated with the harmonic oscillator rigid rotator (HORR) approximation agree with the accurate treatment to within better than 2% in all cases. Results of a variety of electronic structure calculations, including coupled cluster and multireference configuration interaction calculations, with either the HORR approximation or with anharmonicity estimated via second-order vibrational perturbation theory, all agree well with the equilibrium constants obtained from the analytical surfaces. PMID:19290606

  16. Dispersion-corrected first-principles calculation of terahertz vibration, and evidence for weak hydrogen bond formation

    NASA Astrophysics Data System (ADS)

    Takahashi, Masae; Ishikawa, Yoichi; Ito, Hiromasa

    2013-03-01

    A weak hydrogen bond (WHB) such as CH-O is very important for the structure, function, and dynamics in a chemical and biological system WHB stretching vibration is in a terahertz (THz) frequency region Very recently, the reasonable performance of dispersion-corrected first-principles to WHB has been proven. In this lecture, we report dispersion-corrected first-principles calculation of the vibrational absorption of some organic crystals, and low-temperature THz spectral measurement, in order to clarify WHB stretching vibration. The THz frequency calculation of a WHB crystal has extremely improved by dispersion correction. Moreover, the discrepancy in frequency between an experiment and calculation and is 10 1/cm or less. Dispersion correction is especially effective for intermolecular mode. The very sharp peak appearing at 4 K is assigned to the intermolecular translational mode that corresponds to WHB stretching vibration. It is difficult to detect and control the WHB formation in a crystal because the binding energy is very small. With the help of the latest intense development of experimental and theoretical technique and its careful use, we reveal solid-state WHB stretching vibration as evidence for the WHB formation that differs in respective WHB networks A weak hydrogen bond (WHB) such as CH-O is very important for the structure, function, and dynamics in a chemical and biological system WHB stretching vibration is in a terahertz (THz) frequency region Very recently, the reasonable performance of dispersion-corrected first-principles to WHB has been proven. In this lecture, we report dispersion-corrected first-principles calculation of the vibrational absorption of some organic crystals, and low-temperature THz spectral measurement, in order to clarify WHB stretching vibration. The THz frequency calculation of a WHB crystal has extremely improved by dispersion correction. Moreover, the discrepancy in frequency between an experiment and calculation and is 10 1/cm or less. Dispersion correction is especially effective for intermolecular mode. The very sharp peak appearing at 4 K is assigned to the intermolecular translational mode that corresponds to WHB stretching vibration. It is difficult to detect and control the WHB formation in a crystal because the binding energy is very small. With the help of the latest intense development of experimental and theoretical technique and its careful use, we reveal solid-state WHB stretching vibration as evidence for the WHB formation that differs in respective WHB networks The research was supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan (Grant No. 22550003).

  17. Extraction of the vibrational dynamics from the spectra of highly excited molecules and periodic orbit quantization by harmonic inversion

    NASA Astrophysics Data System (ADS)

    Atilgan, Erdinc

    Part I. The effective spectroscopic Hamiltonian fitted to experiment by Troellsch and Temps {A. Troellsch, F. Temps Zeitschrift fuer Physikalische Chemie 215, 207, (2001)} and describing high vibrational excitation to bound and resonant states, is used in conjunction with methods of nonlinear classical dynamics and semiclassical mechanics to extract for all the observed highly excited resonance levels in Polyad 8, the molecular motions upon which they are quantized. Two types of interlaced dynamically distinct ladders of states are revealed. The rungs of these ladders intersperse making the spectra complex. The resonant 2:2:1 frequency ratio of the DC, CO stretches and the bend respectively is what causes the complexity and is what caused past attempts at interpretation to be at best incomplete. All states are assigned with physically meaningful quantum numbers corresponding to quasiconserved quantities. Most interestingly it is pointed out that much of the information and assignment can be done without any calculations at all, using only the qualitative ideas from nonlinear, semiclassical and quantum mechanics along with the information supplied by the experimentalist. Part II. In systems with few degrees of freedom modern quantum calculations are, in general, numerically more efficient than semiclassical methods. However, this situation can be reversed with increasing dimension of the problem. For a three-dimensional system, viz. the hyperbolic four-sphere scattering system, we demonstrate the superiority of semiclassical versus quantum calculations. Semiclassical resonances can easily be obtained even in energy regions which are unattainable with the currently available quantum techniques.

  18. Method for calculating the induced voltage in a vibrating sample magnetometer detection coil system

    NASA Astrophysics Data System (ADS)

    Xu, Xiaonong; Sun, Aimin; Jin, Xin; Fan, Hongchang; Yao, Xixian

    1996-11-01

    A numerical method for obtaining the vibrating sample magnetometer (VSM) sensitivity functions due to a uniformly magnetized sample in the shape of ellipsoid, cuboid or cylinder, and then calculating the induced voltage in a VSM detection coil systems is presented. The induced voltage, which depends on the equilibrium position and amplitude of the sample in three-dimensional space, and depends on the geometric parameters of both sample and detection coils, is calculated from the viewpoint of magnetic charges. This numerical method is more accurate than others, which use dipole moment approximation without taking into consideration the sample shape and size. By using this method, the induced voltage, for which the shape and size effects of the sample must be taken into account, can be calculated if there is knowledge of geometric parameters of the sample and coils. The formulas for calculating the correction coefficient are also given for samples whose shape errors should be considered. Our results provide rigorous theoretical guidance for the exhaustive study of the VSM working principle, for accurate measurement of the sample magnetic moment, and for optimum design of configuration, position, and orientation of VSM pickup coils.

  19. Ab initio calculations on the geometry and OH vibrational frequency shift of cyclic water trimer

    NASA Astrophysics Data System (ADS)

    van Duijneveldt-van de Rijdt, Jeanne G. C. M.; van Duijneveldt, Frans B.

    1993-09-01

    The equilibrium geometrical parameters ROO ? and ? of cyclic water trimer have been determined at the counterpoise corrected SCF+MP2 level in the ESPB basis within pseudo-C 3v symmetry. The final structure has short ( ROO=2.85 Å) and strongly bent (?=20°) hydrogen bonds. The non-bonded OH bonds are directed by ?=48° out of the OOO plane. The interaction energy (? E) is -14.7 kcal mol -1 and the corresponding D0=10.2 kcal mol -1. The likely error bars on these results are discussed. The second order polarization interactions in the trimer are markedly non-additive. The total non-additivity contributes -2.0 kcal mol -1 to the final ? E, and it is responsible for a shortening of ROO by 0.07 Å. Its largest effect (about -70 cm -1) is in the H-bonded OH vibrational frequency shift ?? OH, which at the equilibrium geometry is calculated to be -230 cm -1. The shift is markedly sensitive to the angle ?, and vibrational averaging along this coordinate is expected to reduce ??. The results therefore support Nelander's reassignment of the IR and Raman gas phase OH spectra, which implies ?? OH? -175 cm -1.

  20. Conformational stability, structural parameters, vibrational spectra, and ab initio calculations of isopropyl- and tertiary-butylisothiocyanate

    NASA Astrophysics Data System (ADS)

    Durig, James R.; Zhou, Xiaohua; El Defrawy, Ahmed M.; Guirgis, Gamil A.; Gounev, Todor K.; Zheng, Chao

    2007-08-01

    Variable temperature (-60 to -100 °C) studies of the infrared spectra (3200-400 cm -1) of isopropylisothiocyanate, (CH 3) 2CHNCS, dissolved in liquefied xenon, have been carried out. Additionally the infrared spectra of the gas and solid have been recorded for both isopropylisothiocyanate and tertiary-butylisothiocyanate, (CH 3) 3CNCS, from 3200 to 100 cm -1. The analyses of these spectral data for the isopropyl molecule and the Raman spectrum of the liquid indicated one stable conformer ( trans) in the annealed solid but in the fluid phases most of the molecules have energies above the barriers of the two predicted bound vibrational states i.e., trans and gauche forms. The MP2(full) ab initio calculations, employing a variety of basis sets with and without diffuse functions, have been used to predict the conformational stabilities with the trans conformer, the most stable form, for isopropylisothiocyanate and the second most stable form is predicted to be either the skew or gauche conformer depending in some cases on whether diffuse functions are used. However, even when the energy values indicate the skew form more stable than the gauche rotamer, one imaginary frequency indicates the skew form is a first-order saddle point. These results should be contrasted with the microwave data where the experimental B + C value was previously interpreted to indicate the skew conformer as the most stable form. For t-butylisothiocyanate the staggered conformer is the more stable form with the eclipsed conformer a transition state with a barrier of ˜50 cm -1 so there is nearly free internal rotation of the NCS moiety. For both molecules, the structural parameters, dipole moments, conformational stability, vibrational frequencies, infrared intensities and Raman activities have been predicted from ab initio calculations and complete vibrational assignments are proposed. The r0 structural parameters are estimated by combing the MP2(full)/6-311+G(d,p) predicted values for the CH parameters with some adjustments to the heavy atom distances. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules.

  1. Vibrational spectra, DFT calculations, and conformations of 5?-chloro-1-isopropyl-7-azaindirubin-3?-oxime

    NASA Astrophysics Data System (ADS)

    Robbins, Timothy J.; Wang, Yongmei; Yao, Qi-Zheng; Wang, Zhao-Hui; Cheng, Jingcai; Li, Ying-Sing

    2013-09-01

    For centuries Danggui Longhui Wan has been used to treat chronic ailments, such as myelocytic leukemia. In the 1960s, the active ingredient in Danggui Longhui Wan was isolated and identified as indirubin. Indirubin has shown potent inhibition of cyclin-dependent kinase through binding to the ATP-binding site. However, indirubin shows poor solubility and low absorption, hence many derivatives have been developed to enhance these properties. One such derivative is 5?-chloro-1-isopropyl-7-azaindirubin-3?-oxime (CIADO), investigated in the current work. Infrared and Raman spectra were collected and compared with predicted spectra using density functional theory. Based on theoretical calculations, the most stable form of CIADO isomer is found to be cis (Z) and trans (E) with respect to the ring system linkage and the 3?-oxime functional group respectively. Also observed were two distinct internal rotational minima for the 1-isoprooyl group separated by a large energy barrier. The presence of two distinct isopropyl conformations observed in our calculations was confirmed with temperature-dependent IR experiments. Assignment of experimental vibrational modes was carried out based on functional group displacement observed in the calculations.

  2. Second harmonic generation second hyperpolarizability of water calculated using the combined coupled cluster dielectric continuum or different molecular mechanics methods

    Microsoft Academic Search

    Jacob Kongsted; Anders Osted; Kurt V. Mikkelsen; Ove Christiansen

    2004-01-01

    In this article we report the first calculations of second harmonic generation second hyperpolarizability of liquid water using coupled cluster\\/molecular mechanics (CC\\/MM) methods or coupled cluster\\/dielectric continuum (CC\\/DC) methods. The latter approach treats the solvent as an isotropic homogeneous fluid while the former accounts for the discrete nature of the solvent molecules. The CC\\/MM approach may include or exclude polarization

  3. Variational calculations of rotational-vibrational energies of CH{sub 4} and isotopomers using an adjusted ab initio potential

    SciTech Connect

    Carter, S.; Bowman, J.M.

    2000-03-23

    The authors report variational calculations of vibrational energies of CH{sub 4}, CH{sub 3}D, CH{sub 2}D{sub 2}, CHD{sub 3}, and CD{sub 4} using the code Multimode and the ab initio force field of Lee and co-workers [Lee, T.J.; Martin, J.M.L.; Taylor, P.R.--J.Chem.Phys. 1995, 102, 254], re-expressed using Morse variables in the stretch displacements. Comparisons are made with experimental energies for CH{sub 4} with this potential, and then small adjustments are made to the potential to improve agreement with experiment for CH{sub 4}. Calculations for the isotopomers are done using the adjusted potential and compared with experiment. Additional vibrational energies and assignments not reported experimentally are also given for CH{sub 4} and the isotopomers. Exact rotational-vibrational energies of CH{sub 4} are also reported for J = 1.

  4. The combined use of SCF-MO calculations and frequency data in the evaluation of general harmonic force fields for molecules containing third row elements

    Microsoft Academic Search

    T. H. Arnold; B. I. Swanson; Y. Yamaguchi; D. J. Nelson

    1979-01-01

    The general harmonic force fields of several small molecules containing third row elements have been evaluated using a semiempirical method which combines SCF-MO calculations and limited frequency data. MOCIC (molecular orbital constraint using interaction coordinates) potential fields have been generated using the SCF-MO MNDO method which has recently been parameterized for third row elements. The general harmonic force field (GHFF)

  5. Calculation of the vibration frequencies of alpha-quartz: the effect of Hamiltonian and basis set.

    PubMed

    Zicovich-Wilson, C M; Pascale, F; Roetti, C; Saunders, V R; Orlando, R; Dovesi, R

    2004-11-30

    The central-zone vibrational spectrum of alpha-quartz (SiO2) is calculated by building the Hessian matrix numerically from the analytical gradients of the energy with respect to the atomic coordinates. The nonanalytical part is obtained with a finite field supercell approach for the high-frequency dielectric constant and a Wannier function scheme for the evaluation of Born charges. The results obtained with four different Hamiltonians, namely Hartree-Fock, DFT in its local (LDA) and nonlocal gradient corrected (PBE) approximation, and hybrid B3LYP, are discussed, showing that B3LYP performs far better than LDA and PBE, which in turn provide better results than HF, as the mean absolute difference from experimental frequencies is 6, 18, 21, and 44 cm(-1), respectively, when a split valence basis set containing two sets of polarization functions is used. For the LDA results, comparison is possible with previous calculations based on the Density Functional Perturbation Theory and usage of a plane-wave basis set. The effects associated with the use of basis sets of increasing size are also investigated. It turns out that a split valence plus a single set of d polarization functions provides frequencies that differ from the ones obtained with a double set of d functions and a set of f functions on all atoms by on average less than 5 cm(-1). PMID:15376250

  6. Vibrational spectroscopic studies, NLO, HOMO-LUMO and electronic structure calculations of ?,?,?-trichlorotoluene using HF and DFT

    NASA Astrophysics Data System (ADS)

    Govindarajan, M.; Karabacak, M.; Periandy, S.; Xavier, S.

    FT-IR and FT-Raman spectra of ?,?,?-trichlorotoluene have been recorded and analyzed. The geometry, fundamental vibrational frequencies are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) B3LYP/6-311++G(d,p) method and a comparative study between HF level and various basis sets combination. The fundamental vibrational wavenumbers as well as their intensities were calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. The complete vibrational assignments of wavenumbers are made on the basis of potential energy distribution (PED). The effects due to the substitutions of methyl group and halogen were investigated. The absorption energy and oscillator strength are calculated by time-dependent density functional theory (TD-DFT). The electric dipole moment, polarizability and the first hyperpolarizability values of the ?,?,?-trichlorotoluene have been calculated. 1H NMR chemical shifts were calculated by using the gauge independent atomic orbital (GIAO) method with HF and B3LYP methods with 6-311++G(d,p) basis set. Moreover, molecular electrostatic potential (MEP) and thermodynamic properties were performed. Mulliken and natural charges of the title molecule were also calculated and interpreted.

  7. The Classical Harmonic Vibrations of the Atomic Centers of Mass with Micro Amplitudes and Low Frequencies Monitored by the Entanglement between the Two Two-level Atoms in a Single mode Cavity

    E-print Network

    Yong-Yi Huang

    2013-12-08

    We study the entanglement dynamics of the two two-level atoms coupling with a single-mode polarized cavity field after incorporating the atomic centers of mass classical harmonic vibrations with micro amplitudes and low frequencies. We propose a quantitative vibrant factor to modify the concurrence of the two atoms states. When the vibrant frequencies are very low, we obtain that: (i) the factor depends on the relative vibrant displacements and the initial phases rather than the absolute amplitudes, and reduces the concurrence to three orders of magnitude; (ii) the concurrence increases with the increase of the initial phases; (iii) the frequency of the harmonic vibration can be obtained by measuring the maximal value of the concurrence during a small time. These results indicate that even the extremely weak classical harmonic vibrations can be monitored by the entanglement of quantum states.

  8. Second harmonic generation second hyperpolarizability of water calculated using the combined coupled cluster dielectric continuum or different molecular mechanics methods.

    PubMed

    Kongsted, Jacob; Osted, Anders; Mikkelsen, Kurt V; Christiansen, Ove

    2004-02-22

    In this article we report the first calculations of second harmonic generation second hyperpolarizability of liquid water using coupled cluster/molecular mechanics (CC/MM) methods or coupled cluster/dielectric continuum (CC/DC) methods. The latter approach treats the solvent as an isotropic homogeneous fluid while the former accounts for the discrete nature of the solvent molecules. The CC/MM approach may include or exclude polarization effects explicitly. Alternatively, polarization effects may be included using perturbation theory. The CC descriptions implemented are the coupled cluster second-order approximate singles and doubles (CC2) and coupled cluster singles and doubles models. The second harmonic generation second hyperpolarizabilities are, depending on the model, obtained using either an analytical implementation of the cubic response function or using an analytical implementation of the quadratic response function combined with the finite field technique. The CC/MM results for the second harmonic generation second hyperpolarizability compare excellently with experimental data while a significant overestimation is found when using the CC/DC model. Particular, the cavity radius in the CC/DC calculations have an enormous effects on this fourth-order property. PMID:15268543

  9. Calculation of the structures, stabilities, and vibrational spectra of arsenites, thioarsenites and thioarsenates in aqueous solution

    NASA Astrophysics Data System (ADS)

    Tossell, J. A.; Zimmermann, M. D.

    2008-11-01

    Structures, stabilities and vibrational spectra have been calculated using molecular quantum mechanical methods for As(OH) 3, AsO(OH) 3, As(SH) 3, AsS(SH) 3 and their conjugate bases and for several species with partial substitution of S for O. Properties for the neutral gas-phase molecules are calculated with state-of-the-art methods which yield As sbnd L distances within 0. 01 Å and As sbnd L stretching frequencies within 10 cm -1 of experiment. Similar accuracy is obtained for neutral molecules in solution using a polarizable continuum model (PCM). For monoanions such as AsO(OH)2- and AsS(SH)2-1 frequencies can be calculated to within 20 cm -1 of experiment using the polarizable continuum model. Multiply charged anions remain a challenge for accurate frequency calculations, but we have obtained results within the PCM model which at least semiquantitatively reproduce the available data. This allows us to assign the controversial features D, E and F in the Raman data of (Wood S. A., Tait C. D. and Janecky D. R. (2002) A Raman spectroscopic study of arsenite and thioarsenite species in aqueous solution at 25 °C. Geochem. Trans. 3, 31-39). To help in the assignment of the arsenic sulfide spectra we have also calculated energetics for the oxidation of As(III) to As(V) compounds by polysulfides, disproportionation of As(III) compounds and for the dissociation of the oxo- and thio-acids. We have determined that As(III) oxyacids can be transformed to thioacids which can in turn be oxidized to As(V) sulfides by polysulfides and that the p Ka1s of the acids involved can be ordered as follows: AsS(SH) 3 < As(SH) 3 < AsO(OH) 3 < As(OH) 3 in order of increasing p Ka1. We have also established from the calculated energies that the most stable form of the As(III) oxyacid in acidic aqueous solution is indeed As(OH) 3, consistent with previous assignments.

  10. Effects of broad-banded higher harmonics on fatigue damage of risers due to vortex-induced vibrations

    E-print Network

    Price, Rachel Elizabeth

    2011-01-01

    Recent works have discussed "chaotic" or "Type-II" riser motion and suggested that it is a general feature of VIV riser response. Chaotic riser response contains broad-banded harmonics and a combination of standing and ...

  11. Nonperturbative quantum and classical calculations of multiphoton vibrational excitation and dissociation of Morse molecules^1

    NASA Astrophysics Data System (ADS)

    Dimitriou, K. I.; Mercouris, Th.; Constantoudis, V.; Komninos, Y.; Nicolaides, C. A.

    2006-05-01

    The multiphoton vibrational excitation and dissociation of Morse molecules have been computed nonperturbatively using Hamilton's and Schr?dinger's time-dependent equations, for a range of laser pulse parameters. The time-dependent Schr?dinger equation is solved by the state-specific expansion approach [e.g.,1]. For its solution, emphasis has been given on the inclusion of the continuous spectrum, whose contribution to the multiphoton probabilities for resonance excitation to a number of excited discrete states as well as to dissociation has been examined as a function of laser intensity, frequency and pulse duration. An analysis of possible quantal-classical correspondences for this system is being carried out. We note that distinct features exist from previous classical calculations [2]. For example, the dependence on the laser frequency gives rise to an asymmetry around the red-shifted frequency corresponding to the maximum probability. [1] Th. Mercouris, I. D. Petsalakis and C. A. Nicolaides, J. Phys. B 27, L519 (1994). [2] V. Constantoudis and C. A. Nicolaides, Phys. Rev. E 64, 562112 (2001). ^1This work was supported by the program 'Pythagoras' which is co - funded by the European Social Fund (75%) and Natl. Resources (25%). ^2Physics Department, National Technical University, Athens, Greece.^3Theoretical and Physical Chemistry Institute, Hellenic Research Foundation, Athens, Greece.

  12. Calculation of exact vibrational spectra for P2O and CH2NH using a phase space wavelet basis

    NASA Astrophysics Data System (ADS)

    Halverson, Thomas; Poirier, Bill

    2014-05-01

    ``Exact" quantum dynamics calculations of vibrational spectra are performed for two molecular systems of widely varying dimensionality (P2O and CH2NH), using a momentum-symmetrized Gaussian basis. This basis has been previously shown to defeat exponential scaling of computational cost with system dimensionality. The calculations were performed using the new "SwitchBLADE" black-box code, which utilizes both dimensionally independent algorithms and massive parallelization to compute very large numbers of eigenstates for any fourth-order force field potential, in a single calculation. For both molecules considered here, many thousands of vibrationally excited states were computed, to at least an "intermediate" level of accuracy (tens of wavenumbers). Future modifications to increase the accuracy to "spectroscopic" levels, along with other potential future improvements of the new code, are also discussed.

  13. Calculation of exact vibrational spectra for P2O and CH2NH using a phase space wavelet basis.

    PubMed

    Halverson, Thomas; Poirier, Bill

    2014-05-28

    ''Exact" quantum dynamics calculations of vibrational spectra are performed for two molecular systems of widely varying dimensionality (P2O and CH2NH), using a momentum-symmetrized Gaussian basis. This basis has been previously shown to defeat exponential scaling of computational cost with system dimensionality. The calculations were performed using the new "SwitchBLADE" black-box code, which utilizes both dimensionally independent algorithms and massive parallelization to compute very large numbers of eigenstates for any fourth-order force field potential, in a single calculation. For both molecules considered here, many thousands of vibrationally excited states were computed, to at least an "intermediate" level of accuracy (tens of wavenumbers). Future modifications to increase the accuracy to "spectroscopic" levels, along with other potential future improvements of the new code, are also discussed. PMID:24880271

  14. Empirical maps for the calculation of amide I vibrational spectra of proteins from classical molecular dynamics simulations.

    PubMed

    Ma?olepsza, Edyta; Straub, John E

    2014-07-17

    New sets of parameters (maps) for calculating amide I vibrational spectra for proteins through a vibrational exciton model are proposed. The maps are calculated as a function of electric field and van der Waals forces on the atoms of peptide bonds, taking into account the full interaction between peptide bonds and the surrounding environment. The maps are designed to be employed using data obtained from standard all-atom molecular simulations without any additional constraints on the system. Six proteins representing a wide range of sizes and secondary structure complexity were chosen as a test set. Spectra calculated for these proteins reproduce experimental data both qualitatively and quantitatively. The proposed maps lead to spectra that capture the weak second peak observed in proteins containing ?-sheets, allowing for clear distinction between ?-helical and ?-sheet proteins. While the parametrization is specific to the CHARMM force field, the methodology presented can be readily applied to any empirical force field. PMID:24654732

  15. Time-dependent density-functional-theory calculation of high-order-harmonic generation of H2

    NASA Astrophysics Data System (ADS)

    Chu, Xi; Groenenboom, Gerrit C.

    2012-05-01

    The observation of the isotope effect in the high-order-harmonic generation (HHG) of H2 presents a challenge for time-dependent density-functional-theory (TDDFT) methods, since this effect is related to the dynamics of the ion created in the tunneling ionization step of HHG and it depends on the harmonic order. As an initial step toward describing this effect within current computational capacity, we benchmark a method in which the nuclear and electronic degrees of freedom are separated and both treated quantum mechanically. For the electrons two TDDFT formalisms are adopted. Although the ion-dynamics effect is not described in our method, it reproduces the measured D2-to-H2 HHG ratios up to the 25th harmonic when the 35th is the classical cutoff. Beyond the 25th harmonic, however, our results show substantial deviation and are sensitive to the laser intensity. A higher intensity reproduces the experimental results. Analysis reveals an R-dependent phase factor as the cause of the isotope effect in our calculation. We isolate this phase factor and propose a strong-field-approximation-phase model, which reproduces experimental data, including those for which the ion-dynamics model has to be further modified. We show that the model that we propose is intrinsically related to the ion-dynamics model. Our model provides a correction to the TDDFT approach when the ion-dynamics effect becomes significant. It also indicates that the isotope effect is not only a probe for the ion created by the external field but is ultimately a more useful probe for the ground-state nuclear wave function. For all molecules whose vertical ionization potential strongly depends on the nuclear geometry, HHG may serve as a sensitive ultrafast probe of nuclear dynamics.

  16. Communication: MULTIMODE calculations of low-lying vibrational states of NO3 using an adiabatic potential energy surface

    NASA Astrophysics Data System (ADS)

    Homayoon, Zahra; Bowman, Joel M.

    2014-10-01

    A semi-global, permutationally invariant potential energy surface for NO3 is constructed from a subset of roughly 5000 Multi-State CASPT2 calculations (MS-CAS(17e,13o)PT2/aug-cc-pVTZ) reported by Morokuma and co-workers [H. Xiao, S. Maeda, and K. Morokuma, J. Chem. Theory Comput. 8, 2600 (2012)]. The PES, with empirical adjustments to modify the energies of two fundamentals and a hot-band transition, is used in full-dimensional vibrational self-consistent field/virtual state configuration interaction calculations using the code MULTIMODE. Vibrational energies and assignments are given for the fundamentals and low-lying combination states, including two that have been the focus of some controversy. Energies of a number of overtone and combinations are shown to be in good agreement with experiment and previous calculations using a model vibronic Hamiltonian [C. S. Simmons, T. Ichino, and J. F. Stanton, J. Phys. Chem. Lett. 3, 1946 (2012)]. Notably, the fundamental v3 is calculated to be at 1099 cm-1 in accord with the prediction from the vibronic analysis, although roughly 30 cm-1 higher. The state at 1493 cm-1 is assigned as v3 + v4, which is also in agreement with the vibronic analysis and some experiments. Vibrational energies for 15NO3 are also presented and these are also in good agreement with experiment.

  17. Communication: Towards the binding energy and vibrational red shift of the simplest organic hydrogen bond: harmonic constraints for methanol dimer.

    PubMed

    Heger, Matthias; Suhm, Martin A; Mata, Ricardo A

    2014-09-14

    The discrepancy between experimental and harmonically predicted shifts of the OH stretching fundamental of methanol upon hydrogen bonding to a second methanol unit is too large to be blamed mostly on diagonal and off-diagonal anharmonicity corrections. It is shown that a decisive contribution comes from post-MP2 electron correlation effects, which appear not to be captured by any of the popular density functionals. We also identify that the major deficiency is in the description of the donor OH bond. Together with estimates for the electronic and harmonically zero-point corrected dimer binding energies, this work provides essential constraints for a quantitative description of this simple hydrogen bond. The spectroscopic dissociation energy is predicted to be larger than 18 kJ/mol and the harmonic OH-stretching fundamental shifts by about -121 cm(-1) upon dimerization, somewhat more than in the anharmonic experiment (-111 cm(-1)). PMID:25217897

  18. Communication: Towards the binding energy and vibrational red shift of the simplest organic hydrogen bond: Harmonic constraints for methanol dimer

    SciTech Connect

    Heger, Matthias; Suhm, Martin A.; Mata, Ricardo A., E-mail: rmata@gwdg.de [Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstr. 6, 37077 Göttingen (Germany)

    2014-09-14

    The discrepancy between experimental and harmonically predicted shifts of the OH stretching fundamental of methanol upon hydrogen bonding to a second methanol unit is too large to be blamed mostly on diagonal and off-diagonal anharmonicity corrections. It is shown that a decisive contribution comes from post-MP2 electron correlation effects, which appear not to be captured by any of the popular density functionals. We also identify that the major deficiency is in the description of the donor OH bond. Together with estimates for the electronic and harmonically zero-point corrected dimer binding energies, this work provides essential constraints for a quantitative description of this simple hydrogen bond. The spectroscopic dissociation energy is predicted to be larger than 18 kJ/mol and the harmonic OH-stretching fundamental shifts by about ?121 cm{sup ?1} upon dimerization, somewhat more than in the anharmonic experiment (?111 cm{sup ?1})

  19. Vibrational spectra, theoretical calculations, and two-dimensional potential energy surface for the ring-puckering vibrations of 2,4,7-trioxa[3.3.0]octane.

    PubMed

    Chun, Hye Jin; Meinander, Niklas; Villarreal, John R; Laane, Jaan

    2015-01-15

    2,4,7-Trioxa[3.3.0]octane (247TOO) is an unusual bicyclic molecule which can exist in four different conformational forms which are determined by the directions of the two ring- puckering motions. The vibrational assignments of 247TOO have been made based on its infrared and Raman spectra and theoretical density functional theory (DFT) calculations. The two ring-puckering motions (in-phase and out-of-phase) were observed in the Raman spectra of the liquid at 249 and 205 cm(-1) and these values correspond well to the DFT values of 247 and 198 cm(-1). Ab initio calculations were utilized to calculate the structures and conformational energies for the four energy minima and the barriers to interconversion and the data was utilized to generate a two-dimensional potential energy surface (PES) for the two ring-puckering motions. The resulting quantum state energies for this PES were then calculated in order to better understand the patterns that are produced when the PES has four energy minima at different energy values. The wave functions corresponding to the different quantum states were also calculated. The NMR spectrum of 247TOO showed the presence of the two lowest energy conformations, consistent with the results of the ab initio calculations. PMID:25514365

  20. Conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of 2-chloropropenoyl fluoride

    NASA Astrophysics Data System (ADS)

    Durig, J. R.; Wang, A. Y.; Little, T. S.; Brletic, P. A.

    1990-07-01

    The far-infrared spectrum of gaseous 2-chloropropenoyl fluoride, CH2 CClCFO, has been recorded at a resolution of 0.10 cm-1 in the region of 350-35 cm-1. The fundamental asymmetric torsional frequencies of the more stable s-trans (two double bonds oriented trans to one another) and the high energy s-cis conformations have been observed at 67.80 and 49.96 cm-1, respectively, each with several excited states falling to lower frequencies. From these data the asymmetric torsional potential function governing the internal rotation about the C-C bond has been determined. The potential coefficients are V1 =-125±1, V2 =1586±6, V3 =375±2, V4 =-36±2, and V5 =-65±1 cm-1. The s-trans to s-cis and s-cis to s-trans barriers have been determined to be 1755 and 1570 cm-1, respectively, with an energy difference between the conformations of 185±9 cm-1 (529±26 cal/mol). From studies of the Raman spectrum at variable temperatures, the conformational enthalpy difference has been determined to be 176±40 cm-1 (503±114 cal/mol) and 625±51 cm-1 (1787±146 cal/mol) for the gas and liquid, respectively. A complete assignment of the vibrational fundamentals observed from the infrared spectra (3500-50 cm-1) of the gas and solid and the Raman spectra (3200-10 cm-1) of all three physical states is proposed. All of these data are compared to the corresponding quantities obtained from ab initio Hartree-Fock gradient calculations employing both the 3-21G* and 6-31G* basis sets. Additionally, complete equilibrium geometries have been determined for both rotamers. The results are discussed and compared with the corresponding quantities obtained for some similar molecules.

  1. FT-IR and FT-Raman spectroscopic investigation, computed vibrational frequency analysis and IR intensity and Raman activity peak resemblance analysis on 2-nitroanisole using HF and DFT (B3LYP and B3PW91) calculations

    NASA Astrophysics Data System (ADS)

    Prabhu, T.; Periandy, S.; Ramalingam, S.

    2011-12-01

    Fourier-transform Raman and infrared spectra of 2-nitroanisole are recorded (4000-100 cm -1) and interpreted by comparison with respective theoretical spectra calculated using HF and DFT method. The geometrical parameters with CS symmetry, harmonic vibrational frequencies, infrared and Raman scattering intensities are determined using HF/6-311++G (d, p), B3LYP/6-311+G (d, p), B3LYP/6-311++G (d, p) and B3PW91/6-311++G (d, p) level of theories. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The SQM method, which implies multiple scaling of the DFT force fields has been shown superior to the uniform scaling approach. The vibrational frequencies and the infrared intensities of the C-H modes involved in back-donation and conjugation are also investigated.

  2. FT-IR and FT-Raman spectroscopic investigation, computed vibrational frequency analysis and IR intensity and Raman activity peak resemblance analysis on 2-nitroanisole using HF and DFT (B3LYP and B3PW91) calculations.

    PubMed

    Prabhu, T; Periandy, S; Ramalingam, S

    2011-12-01

    Fourier-transform Raman and infrared spectra of 2-nitroanisole are recorded (4000-100 cm(-1)) and interpreted by comparison with respective theoretical spectra calculated using HF and DFT method. The geometrical parameters with C(S) symmetry, harmonic vibrational frequencies, infrared and Raman scattering intensities are determined using HF/6-311++G (d, p), B3LYP/6-311+G (d, p), B3LYP/6-311++G (d, p) and B3PW91/6-311++G (d, p) level of theories. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The SQM method, which implies multiple scaling of the DFT force fields has been shown superior to the uniform scaling approach. The vibrational frequencies and the infrared intensities of the C-H modes involved in back-donation and conjugation are also investigated. PMID:21963192

  3. Calculation of the vibrational spectra of RDX as a function of pressure using the Grimme DFT potential

    NASA Astrophysics Data System (ADS)

    Perger, Warren; Flurchick, K. M.; Slough, Wil; Valenzano, Loredana

    2011-06-01

    The density-functional theory (DFT) potential by Grimme has been proposed for describing long-range dispersion corrections. This potential has been implemented into the CRYSTAL09 program and used to calculate the vibrational spectra in RDX at equilibrium and as a function of pressure. The intensities, Born charge tensor, and high-frequency dielectric constant are reported and compared with prior theory and experiment where possible. Supported by ONR-MURI grant N00014-06-1-0459.

  4. Structure and vibrational spectra of melaminium bis(trifluoroacetate) trihydrate: FT-IR, FT-Raman and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Sangeetha, V.; Govindarajan, M.; Kanagathara, N.; Marchewka, M. K.; Gunasekaran, S.; Anbalagan, G.

    Melaminium bis(trifluoroacetate) trihydrate (MTFA), an organic material has been synthesized and single crystals of MTFA have been grown by the slow solvent evaporation method at room temperature. X-ray powder diffraction analysis confirms that MTFA crystal belongs to the monoclinic system with space group P2/c. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on density functional theory (DFT) B3LYP method with 6-311G(d,p) and 6-311++G(d,p) basis sets. The X-ray diffraction data have been compared with the data of optimized molecular structure. The theoretical results show that the crystal structure can be reproduced by optimized geometry and the vibrational frequencies show good agreement with the experimental values. The nuclear magnetic resonance (NMR) chemical shift of the molecule has been calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. HOMO-LUMO, and other related molecular and electronic properties are calculated. The Mulliken and NBO charges have also been calculated and interpreted.

  5. Structure and vibrational spectra of melaminium bis(trifluoroacetate) trihydrate: FT-IR, FT-Raman and quantum chemical calculations.

    PubMed

    Sangeetha, V; Govindarajan, M; Kanagathara, N; Marchewka, M K; Gunasekaran, S; Anbalagan, G

    2014-05-01

    Melaminium bis(trifluoroacetate) trihydrate (MTFA), an organic material has been synthesized and single crystals of MTFA have been grown by the slow solvent evaporation method at room temperature. X-ray powder diffraction analysis confirms that MTFA crystal belongs to the monoclinic system with space group P2/c. The molecular geometry, vibrational frequencies and intensity of the vibrational bands have been interpreted with the aid of structure optimization based on density functional theory (DFT) B3LYP method with 6-311G(d,p) and 6-311++G(d,p) basis sets. The X-ray diffraction data have been compared with the data of optimized molecular structure. The theoretical results show that the crystal structure can be reproduced by optimized geometry and the vibrational frequencies show good agreement with the experimental values. The nuclear magnetic resonance (NMR) chemical shift of the molecule has been calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. HOMO-LUMO, and other related molecular and electronic properties are calculated. The Mulliken and NBO charges have also been calculated and interpreted. PMID:24556134

  6. Studies on vibrational, NMR spectra and quantum chemical calculations of N-Succinopyridine: An organic nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Kannan, V.; Thirupugalmani, K.; Brahadeeswaran, S.

    2013-10-01

    Single crystals of N-Succinopyridine (NSP) have been grown from water using solution growth method by isothermal solvent evaporation technique. The solid state Fourier Transform Infrared (FTIR) spectrum of the grown crystal shows a broad absorption extending from 3450 down to 400 cm-1, due to H-bond vibrations and other characteristic vibrations. Fourier Transform Raman (FT-Raman) spectrum of NSP single crystal shows Raman intensities ranging from 3100 to 100 cm-1 due the characteristics vibrations of functional groups present in NSP. The proton and carbon positions of NSP have been described by 1H and 13C NMR spectrum respectively. Ab initio quantum chemical calculations on NSP have been performed by density functional theory (DFT) calculations using B3LYP method with 6-311++G(d,p) basis set. The predicted first hyperpolarizability is found to be 1.29 times greater than that of urea and suggests that the title compound could be an attractive material for nonlinear optical applications. The calculated HOMO-LUMO energies show that charge transfers occur within the molecule and other related molecular properties. Molecular properties such as Mulliken population analysis, thermodynamic functions and perturbation theory energy analysis have also been reported. Electrostatic potential map (ESP) of NSP obtained by electron density isosurface provided the information about the size, shape, charge density distribution and site of chemical reactivity of the title molecule. The molecular stability and bond strength have been investigated through the Natural Bond Orbital (NBO) analysis.

  7. A complete assignment of the vibrational spectra of sucrose in aqueous medium based on the SQM methodology and SCRF calculations.

    PubMed

    Brizuela, Alicia Beatriz; Castillo, María Victoria; Raschi, Ana Beatriz; Davies, Lilian; Romano, Elida; Brandán, Silvia Antonia

    2014-03-31

    In the present study, a complete assignment of the vibrational spectra of sucrose in aqueous medium was performed combining Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology with self-consistent reaction field (SCRF) calculations. Aqueous saturated solutions of sucrose and solutions at different molar concentrations of sucrose in water were completely characterized by infrared, HATR, and Raman spectroscopies. In accordance with reported data of the literature for sucrose, the theoretical structures of sucrose penta and sucrose dihydrate were also optimized in gas and aqueous solution phases by using the density functional theory (DFT) calculations. The solvent effects for the three studied species were analyzed using the solvation PCM/SMD model and, then, their corresponding solvation energies were predicted. The presence of pure water, sucrose penta-hydrate, and sucrose dihydrate was confirmed by using theoretical calculations based on the hybrid B3LYP/6-31G(?) method and the experimental vibrational spectra. The existence of both sucrose hydrate complexes in aqueous solution is evidenced in the IR and HATR spectra by means of the characteristic bands at 3388, 3337, 3132, 1648, 1375, 1241, 1163, 1141, 1001, 870, 851, 732, and 668cm(-1) while in the Raman spectrum, the groups of bands in the regions 3159-3053cm(-1), 2980, 2954, and 1749-1496cm(-1) characterize the vibration modes of those complexes. The inter and intra-molecular H bond formations in aqueous solution were studied by Natural Bond Orbital (NBO) and Atoms in Molecules theory (AIM) investigation. PMID:24632216

  8. Structural, vibrational, and quasiparticle band structure of 1,1-diamino-2,2-dinitroethelene from ab initio calculations.

    PubMed

    Appalakondaiah, S; Vaitheeswaran, G; Lebègue, S

    2014-01-01

    The effects of pressure on the structural and vibrational properties of the layered molecular crystal 1,1-diamino-2,2-dinitroethelene (FOX-7) are explored by first principles calculations. We observe significant changes in the calculated structural properties with different corrections for treating van der Waals interactions to Density Functional Theory (DFT), as compared with standard DFT functionals. In particular, the calculated ground state lattice parameters, volume and bulk modulus obtained with Grimme's scheme, are found to agree well with experiments. The calculated vibrational frequencies demonstrate the dependence of the intra and inter-molecular interactions on FOX-7 under pressure. In addition, we also found a significant increment in the N-H...O hydrogen bond strength under compression. This is explained by the change in bond lengths between nitrogen, hydrogen, and oxygen atoms, as well as calculated IR spectra under pressure. Finally, the computed band gap is about 2.3 eV with generalized gradient approximation, and is enhanced to 5.1 eV with the GW approximation, which reveals the importance of performing quasiparticle calculations in high energy density materials. PMID:24410219

  9. Terahertz spectroscopy and solid-state density functional theory calculation of anthracene: Effect of dispersion force on the vibrational modes

    SciTech Connect

    Zhang, Feng; Tominaga, Keisuke, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-0013 (Japan)] [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-0013 (Japan); Hayashi, Michitoshi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp; Wang, Houng-Wei [Center for Condensed Matter Sciences, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China)] [Center for Condensed Matter Sciences, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China); Kambara, Ohki; Sasaki, Tetsuo [Research Institute of Electronics, Shizuoka University, 3-5-1 Jyohoku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan)] [Research Institute of Electronics, Shizuoka University, 3-5-1 Jyohoku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Nishizawa, Jun-ichi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Jun-ichi Nishizawa Memorial Research Center, Tohoku University, 519-1176 Aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)] [Jun-ichi Nishizawa Memorial Research Center, Tohoku University, 519-1176 Aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)

    2014-05-07

    The phonon modes of molecular crystals in the terahertz frequency region often feature delicately coupled inter- and intra-molecular vibrations. Recent advances in density functional theory such as DFT-D{sup *} have enabled accurate frequency calculation. However, the nature of normal modes has not been quantitatively discussed against experimental criteria such as isotope shift (IS) and correlation field splitting (CFS). Here, we report an analytical mode-decoupling method that allows for the decomposition of a normal mode of interest into intermolecular translation, libration, and intramolecular vibrational motions. We show an application of this method using the crystalline anthracene system as an example. The relationship between the experimentally obtained IS and the IS obtained by PBE-D{sup *} simulation indicates that two distinctive regions exist. Region I is associated with a pure intermolecular translation, whereas region II features coupled intramolecular vibrations that are further coupled by a weak intermolecular translation. We find that the PBE-D{sup *} data show excellent agreement with the experimental data in terms of IS and CFS in region II; however, PBE-D{sup *} produces significant deviations in IS in region I where strong coupling between inter- and intra-molecular vibrations contributes to normal modes. The result of this analysis is expected to facilitate future improvement of DFT-D{sup *}.

  10. Scaled Quantum Mechanical scale factors for vibrational calculations using alternate polarized and augmented basis sets with the B3LYP density functional calculation model

    NASA Astrophysics Data System (ADS)

    Legler, C. R.; Brown, N. R.; Dunbar, R. A.; Harness, M. D.; Nguyen, K.; Oyewole, O.; Collier, W. B.

    2015-06-01

    The Scaled Quantum Mechanical (SQM) method of scaling calculated force constants to predict theoretically calculated vibrational frequencies is expanded to include a broad array of polarized and augmented basis sets based on the split valence 6-31G and 6-311G basis sets with the B3LYP density functional. Pulay's original choice of a single polarized 6-31G(d) basis coupled with a B3LYP functional remains the most computationally economical choice for scaled frequency calculations. But it can be improved upon with additional polarization functions and added diffuse functions for complex molecular systems. The new scale factors for the B3LYP density functional and the 6-31G, 6-31G(d), 6-31G(d,p), 6-31G+(d,p), 6-31G++(d,p), 6-311G, 6-311G(d), 6-311G(d,p), 6-311G+(d,p), 6-311G++(d,p), 6-311G(2d,p), 6-311G++(2d,p), 6-311G++(df,p) basis sets are shown. The double d polarized models did not perform as well and the source of the decreased accuracy was investigated. An alternate system of generating internal coordinates that uses the out-of plane wagging coordinate whenever it is possible; makes vibrational assignments via potential energy distributions more meaningful. Automated software to produce SQM scaled vibrational calculations from different molecular orbital packages is presented.

  11. Vibrational investigation on FT-IR and FT-Raman spectra, IR intensity, Raman activity, peak resemblance, ideal estimation, standard deviation of computed frequencies analyses and electronic structure on 3-methyl-1,2-butadiene using HF and DFT (LSDA/B3LYP/B3PW91) calculations

    NASA Astrophysics Data System (ADS)

    Ramalingam, S.; Jayaprakash, A.; Mohan, S.; Karabacak, M.

    2011-11-01

    FT-IR and FT-Raman (4000-100 cm -1) spectral measurements of 3-methyl-1,2-butadiene (3M12B) have been attempted in the present work. Ab-initio HF and DFT (LSDA/B3LYP/B3PW91) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, IR intensities and Raman activities. Complete vibrational assignments on the observed spectra are made with vibrational frequencies obtained by HF and DFT (LSDA/B3LYP/B3PW91) at 6-31G(d,p) and 6-311G(d,p) basis sets. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The potential energy distribution (PED) corresponding to each of the observed frequencies are calculated which confirms the reliability and precision of the assignment and analysis of the vibrational fundamentals modes. The oscillation of vibrational frequencies of butadiene due to the couple of methyl group is also discussed. A study on the electronic properties such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties of the title compound at different temperatures reveal the correlations between standard heat capacities ( C) standard entropies ( S), and standard enthalpy changes ( H).

  12. Vibrational investigation on FT-IR and FT-Raman spectra, IR intensity, Raman activity, peak resemblance, ideal estimation, standard deviation of computed frequencies analyses and electronic structure on 3-methyl-1,2-butadiene using HF and DFT (LSDA/B3LYP/B3PW91) calculations.

    PubMed

    Ramalingam, S; Jayaprakash, A; Mohan, S; Karabacak, M

    2011-11-01

    FT-IR and FT-Raman (4000-100 cm(-1)) spectral measurements of 3-methyl-1,2-butadiene (3M12B) have been attempted in the present work. Ab-initio HF and DFT (LSDA/B3LYP/B3PW91) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, IR intensities and Raman activities. Complete vibrational assignments on the observed spectra are made with vibrational frequencies obtained by HF and DFT (LSDA/B3LYP/B3PW91) at 6-31G(d,p) and 6-311G(d,p) basis sets. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The potential energy distribution (PED) corresponding to each of the observed frequencies are calculated which confirms the reliability and precision of the assignment and analysis of the vibrational fundamentals modes. The oscillation of vibrational frequencies of butadiene due to the couple of methyl group is also discussed. A study on the electronic properties such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties of the title compound at different temperatures reveal the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H). PMID:21813316

  13. Calculation of the vibrationally resolved, circularly polarized luminescence of d-camphorquinone and (S,S)-trans-beta-hydrindanone.

    PubMed

    Pritchard, Benjamin; Autschbach, Jochen

    2010-08-01

    Circularly polarized luminescence (CPL), the differential emission of left- and right-handed circularly polarized light from a molecule, is modeled by using time-dependent density functional theory. Calculations of the CPL spectra for the first electronic excited states of d-camphorquinone and (S,S)-trans-beta-hydrindanone under the Franck-Condon approximation and using various functionals are presented, as well as calculations of absorption, emission, and circular dichroism spectra. The functionals B3LYP, BHLYP, and CAM-B3LYP are employed, along with the TZVP and aug-cc-pVDZ Gaussian-type basis sets. For the lowest-energy transitions, all functionals and basis sets perform comparably, with the long-range-corrected CAM-B3LYP better reproducing the excitation energy of camphorquinone but leading to a blue shift with respect to experiment for hydrindanone. The vibrationally resolved spectra of camphorquinone are very well reproduced in terms of peak location, widths, shapes, and intensities. The spectra of hydrindanone are well reproduced in terms of overall envelope shape and width, as well as the lack of prominent vibrational structure in the emission and CPL spectra. Overall the simulated spectra compare well with experiment, and reproduce the band shapes, emission red shifts, and presence or absence of visible vibrational fine structure. PMID:20632354

  14. Vibrational analysis of helical poly-L-alanine: Improvement of an empirical harmonic force field for peptides and proteins

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Ho

    1997-08-01

    Vibrational normal modes of regular helical polymers are characterized by A, E1, and E2 symmetry species where A and E1 modes are infrared active and A, E1, and E2 modes are Raman active. For uniaxially oriented ?-poly-L-alanine (?- PLA) samples and their N-deuterated analogues, polarized vibrational (Raman, infrared, and far-infrared) spectra corresponding to each of these optically active symmetry species were measured. Different from previous studies for ?-PLA, in addition to the usual ? I-helix conformation corresponding to the X-ray crystallographically determined structure, our excellent spectral data show another helical conformation occupying about 40% of the PLA sample. Meanwhile, recent advances in computational physics make it possible to compute the vibrational force field by ab initio quantum mechanical methods. In an effort to find a vibrational force field for polypeptides and proteins, based both on the ab initio force fields for small peptides like trans-N-methylacetamide and alanine dipeptides and on the new experimental data, a rigorous vibrational analysis has been done for the ? I-helix first. A compact vibrational formalism up to the cubic anharmonic terms for a regular helix was developed as well as analytic formulas for computation of higher order B-matrix elements. By using this, a more accurate Fermi- Dennison resonance analysis has been possible in the observed amide A band than was the case in previous studies. The direct nonbonded-interaction force constants, introduced to reproduce observed splittings among symmetry species for amide I and II modes, give a more accurate and simple transition-dipole coupling description than does the previous perturbation treatment. All the assigned bands are well reproduced within 5 cm-1 as a result of the least-squares refinement process on the initial force field taken from the ab initio peptide force fields, and the resulting refined force field for the ? I-helix also well explains the observed inelastic neutron scattering spectra for ?-PLA samples. In order to determine the unknown helical structure, the refined force field for the ? I-PLA structure has been applied to the candidate right-handed structures of ? II-, 310-B, and 310-P helices. The 310-helix is the most likely candidate for this additional structure.

  15. M-shaped asymmetric nonlinear oscillator for broadband vibration energy harvesting: Harmonic balance analysis and experimental validation

    NASA Astrophysics Data System (ADS)

    Leadenham, S.; Erturk, A.

    2014-11-01

    Over the past few years, nonlinear oscillators have been given growing attention due to their ability to enhance the performance of energy harvesting devices by increasing the frequency bandwidth. Duffing oscillators are a type of nonlinear oscillator characterized by a symmetric hardening or softening cubic restoring force. In order to realize the cubic nonlinearity in a cantilever at reasonable excitation levels, often an external magnetic field or mechanical load is imposed, since the inherent geometric nonlinearity would otherwise require impractically high excitation levels to be pronounced. As an alternative to magnetoelastic structures and other complex forms of symmetric Duffing oscillators, an M-shaped nonlinear bent beam with clamped end conditions is presented and investigated for bandwidth enhancement under base excitation. The proposed M-shaped oscillator made of spring steel is very easy to fabricate as it does not require extra discrete components to assemble, and furthermore, its asymmetric nonlinear behavior can be pronounced yielding broadband behavior under low excitation levels. For a prototype configuration, linear and nonlinear system parameters extracted from experiments are used to develop a lumped-parameter mathematical model. Quadratic damping is included in the model to account for nonlinear dissipative effects. A multi-term harmonic balance solution is obtained to study the effects of higher harmonics and a constant term. A single-term closed-form frequency response equation is also extracted and compared with the multi-term harmonic balance solution. It is observed that the single-term solution overestimates the frequency of upper saddle-node bifurcation point and underestimates the response magnitude in the large response branch. Multi-term solutions can be as accurate as time-domain solutions, with the advantage of significantly reduced computation time. Overall, substantial bandwidth enhancement with increasing base excitation is validated experimentally, analytically, and numerically. As compared to the 3 dB bandwidth of the corresponding linear system with the same linear damping ratio, the M-shaped oscillator offers 3200, 5600, and 8900 percent bandwidth enhancement at the root-mean-square base excitation levels of 0.03g, 0.05g, and 0.07g, respectively. The M-shaped configuration can easily be exploited in piezoelectric and electromagnetic energy harvesting as well as their hybrid combinations due to the existence of both large strain and kinetic energy regions. A demonstrative case study is given for electromagnetic energy harvesting, revealing the importance of higher harmonics and the need for multi-term harmonic balance analysis for predicting the electrical power output accurately.

  16. Vibrational Spectra of Water Solutions of Azoles from QM/MM Calculations: Effects of Solvation

    E-print Network

    Guidoni, Leonardo

    of two azoles in water solution: pyrazole and oxazole. The effects of the water-azole hydrogen bonding to investigate the solvation effect on the vibrational properties of a prototype of azole, pyrazole (see Figure 1 surround pyrazole through NH···O and N···HO hydrogen bonds inducing significant changes in the geometrical

  17. On the problem of the vibrational spectrum and structure of ice Ih: Lattice dynamical calculations

    Microsoft Academic Search

    Paola Bosi; Riccardo Tubino; Giuseppe Zerbi

    1973-01-01

    It is experimentally known that ice Ih is orientationally disordered. The vibrational spectrum has been previously interpreted by other authors in terms of a simplified point mass model. On the basis of this model long-range forces, spectral activation by the disorder, fluctuating ordered polar domains, etc., were proposed. We present in this paper the results of a lattice dynamical treatment

  18. Theoretical investigations on molecular structure, vibrational spectra, HOMO, LUMO, NBO analysis and hyperpolarizability calculations of thiophene-2-carbohydrazide.

    PubMed

    Balachandran, V; Janaki, A; Nataraj, A

    2014-01-24

    The Fourier-Transform infrared and Fourier-Transform Raman spectra of thiophene-2-carbohydrazide (TCH) was recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1). Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of TCH were carried out by DFT (B3LYP) method with 6-311++G(d,p) as basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. Stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV spectrum was measured in different solvent. The energy and oscillator strength are calculated by Time Dependant Density Functional Theory (TD-DFT) results. The calculated HOMO and LUMO energies also confirm that charge transfer occurs within the molecule. The complete assignments were performed on the basis of the potential energy distribution (PED) of vibrational modes, calculated with scaled quantum mechanics (SQM) method. Finally the theoretical FT-IR, FT-Raman, and UV spectra of the title molecule have also been constructed. PMID:24060478

  19. Vibration--rotation relaxation in bimolecular collisions with application to para-hydrogen. [Three-dimensional quantum mechanical calculations, effective-potential approximation, energy transfer, cross sections, rates

    Microsoft Academic Search

    R. Ramaswamy; H. Rabitz

    1977-01-01

    Three-dimensional quantum mechanical calculations in the effective potential approximation have been made on the para-hydrogen system. At low temperatures, vib--rotationally inelastic collisions were examined while breathing sphere calculations were used to probe the high-temperature regime. It was found that simultaneous vibrational and rotational processes contribute to the overall mechanism of vibrational relaxation. Collisionally induced intra- and intermolecular energy transfer is

  20. DVR3D: a program suite for the calculation of rotation-vibration spectra of triatomic molecules

    NASA Astrophysics Data System (ADS)

    Tennyson, Jonathan; Kostin, Maxim A.; Barletta, Paolo; Harris, Gregory J.; Polyansky, Oleg L.; Ramanlal, Jayesh; Zobov, Nikolai F.

    2004-11-01

    The DVR3D program suite calculates energy levels, wavefunctions, and where appropriate dipole transition moments, for rotating and vibrating triatomic molecules. Potential energy and, where necessary, dipole surfaces must be provided. Expectation values of geometrically defined functions can be calculated, a feature which is particularly useful for fitting potential energy surfaces. The programs use an exact (within the Born-Oppenheimer approximation) Hamiltonian and offer a choice of Jacobi or Radau internal coordinates and several body-fixed axes. Rotationally excited states are treated using an efficient two-step algorithm. The programs uses a Discrete Variable Representation (DVR) based on Gauss-Jacobi and Gauss-Laguerre quadrature for all 3 internal coordinates and thus yields a fully point-wise representation of the wavefunctions. The vibrational step uses successive diagonalisation and truncation which is implemented for a number of possible coordinate orderings. The rotational, expectation value and transition dipole programs exploit the savings offered by performing integrals on a DVR grid. The new version has been rewritten in FORTRAN 90 to exploit the dynamic array allocations and the algorithm for dipole and spectra calculations have been substantially improved. New modules allow the z-axis to be embedded perpendicular to the plane of the molecule and for the calculation of expectation values. Program summaryTitle of the program: DVR3D suite Catalogue number: ADTI Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTI Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Programming language: Fortran 90 No. of lines in distributed program, including test data, etc.: 61 574 No. of bytes in distributed program, including test data, etc.: 972 404 Distribution format: tar.gz New version summaryTitle of program: DVR3DRJZ Catalogue number: ADTB Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTB Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Reference in CPC to previous version: 86 (1995) 175 Catalogue identifier of previous version: ADAK Authors of previous version: J. Tennyson, J.R. Henderson and N.G. Fulton Does the new version supersede the original program?: DVR3DRJZ supersedes DVR3DRJ Computer: PC running Linux Installation: desktop Other machines on which program tested: Compaq running True64 Unix; SGI Origin 2000, Sunfire V750 and V880 systems running SunOS, IBM p690 Regatta running AIX Programming language used in the new version: Fortran 90 Memory required to execute: case dependent No. of lines in distributed program, including test data, etc.: 4203 No. of bytes in distributed program, including test data, etc.: 30 087 Has code been vectorised or parallelised?: The code has been extensively vectorised. A parallel version of the code, PDVR3D has been developed [1], contact the first author for details Additional keywords: perpendicular embedding Distribution format: gz Nature of physical problem: DVR3DRJZ calculates the bound vibrational or Coriolis decoupled rotational-vibrational states of a triatomic system in body-fixed Jacobi (scattering) or Radau coordinates [2] Method of solution: All coordinates are treated in a discrete variable representation (DVR). The angular coordinate uses a DVR based on (associated) Legendre polynomials and the radial coordinates utilise a DVR based on either Morse oscillator-like or spherical oscillator functions. Intermediate diagonalisation and truncation is performed on the hierarchical expression of the Hamiltonian operator to yield the final secular problem. DVR3DRJ provides the vibrational wavefunctions necessary for ROTLEV3, ROLEV3B or ROTLEV3Z to calculate rotationally excited states, DIPOLE3 to calculate rotational-vibrational transition strengths and XPECT3 to compute expectation values Restrictions on the complexity of the problem: (1) The size of the final Hamiltonian matrix that can practically be diagonalised. (2) The order of integration in the radial coordinates that can b

  1. Efficient and robust calculation of femtoscopic correlation functions in spherical harmonics directly from the raw pairs measured in heavy-ion collisions

    E-print Network

    Adam Kisiel; David A. Brown

    2009-12-07

    We present the formalism for calculating the femtoscopic correlation function directly in spherical harmonics. The numerator and denominator are stored as a set of one-dimensional histograms representing the spherical harmonic decompositions of each. We present the formalism to calculate the correlation function from them directly, without going to any three-dimensional histogram. We discuss the practical implementation of the method and we provide an example of its use. We also discuss the stability of the method in the presence of $\\theta$-$\\phi$ holes in the underlying data (e.g. from experimental acceptance).

  2. Conformational and Vibrational Studies of Triclosan

    NASA Astrophysics Data System (ADS)

    Özi?ik, Haci; Bayari, S. Haman; Sa?lam, Semran

    2010-01-01

    The conformational equilibrium of triclosan (5-chloro-2-(2, 4-dichlorophenoxy) phenol) have been calculated using density functional theory (DFTe/B3LYP/6-311++G(d, p)) method. Four different geometries were found to correspond to energy minimum conformations. The IR spectrum of triclosan was measured in the 4000-400 cm-1 region. We calculated the harmonic frequencies and intensities of the most stable conformers in order to assist in the assignment of the vibrational bands in the experimental spectrum. The fundamental vibrational modes were characterized depending on their total energy distribution (TED%) using scaled quantum mechanical (SQM) force field method.

  3. A Comparison of Calculations and Measurements of the Field Harmonics as a

    E-print Network

    Gupta, Ramesh

    and 50 mm aperture dipole magnets. The primary purpose of this paper is to examine the iron saturation to estimate the uncertainty in the computer calculations. It may be noted that in the present yoke design relocating and/or re-sizing the stainless steel key at the midplane which aligns the top and bottom yoke

  4. Robust optimization of an automobile rearview mirror for vibration reduction

    Microsoft Academic Search

    K.-H. Hwang; K.-W. Lee; G.-J. Park

    2001-01-01

    .   An automobile outside rearview mirror system has been analysed and designed to reduce vibration with a finite element model.\\u000a Modal analysis is conducted for the calculation of natural frequencies. Harmonic analysis is utilized to estimate the displacements\\u000a of the glass surface under dynamic loads. The model is verified with the vibration experiment for the parts and the assembled\\u000a body.

  5. Multi-layer Lanczos iteration approach to calculations of vibrational energies and dipole transition intensities for polyatomic molecules.

    PubMed

    Yu, Hua-Gen

    2015-01-28

    We report a rigorous full dimensional quantum dynamics algorithm, the multi-layer Lanczos method, for computing vibrational energies and dipole transition intensities of polyatomic molecules without any dynamics approximation. The multi-layer Lanczos method is developed by using a few advanced techniques including the guided spectral transform Lanczos method, multi-layer Lanczos iteration approach, recursive residue generation method, and dipole-wavefunction contraction. The quantum molecular Hamiltonian at the total angular momentum J = 0 is represented in a set of orthogonal polyspherical coordinates so that the large amplitude motions of vibrations are naturally described. In particular, the algorithm is general and problem-independent. An application is illustrated by calculating the infrared vibrational dipole transition spectrum of CH4 based on the ab initio T8 potential energy surface of Schwenke and Partridge [Spectrochimica Acta, Part A 57, 887 (2001)] and the low-order truncated ab initio dipole moment surfaces of Yurchenko et al. [J. Mol. Spectrosc. 291, 69 (2013)]. A comparison with experiments is made. The algorithm is also applicable for Raman polarizability active spectra. PMID:25637968

  6. Calculation of vibrational shifts of nitrile probes in the active site of ketosteroid isomerase upon ligand binding.

    PubMed

    Layfield, Joshua P; Hammes-Schiffer, Sharon

    2013-01-16

    The vibrational Stark effect provides insight into the roles of hydrogen bonding, electrostatics, and conformational motions in enzyme catalysis. In a recent application of this approach to the enzyme ketosteroid isomerase (KSI), thiocyanate probes were introduced in site-specific positions throughout the active site. This paper implements a quantum mechanical/molecular mechanical (QM/MM) approach for calculating the vibrational shifts of nitrile (CN) probes in proteins. This methodology is shown to reproduce the experimentally measured vibrational shifts upon binding of the intermediate analogue equilinen to KSI for two different nitrile probe positions. Analysis of the molecular dynamics simulations provides atomistic insight into the roles that key residues play in determining the electrostatic environment and hydrogen-bonding interactions experienced by the nitrile probe. For the M116C-CN probe, equilinen binding reorients an active-site water molecule that is directly hydrogen-bonded to the nitrile probe, resulting in a more linear C?N--H angle and increasing the CN frequency upon binding. For the F86C-CN probe, equilinen binding orients the Asp103 residue, decreasing the hydrogen-bonding distance between the Asp103 backbone and the nitrile probe and slightly increasing the CN frequency. This QM/MM methodology is applicable to a wide range of biological systems and has the potential to assist in the elucidation of the fundamental principles underlying enzyme catalysis. PMID:23210919

  7. Multi-layer Lanczos iteration approach to calculations of vibrational energies and dipole transition intensities for polyatomic molecules

    DOE PAGESBeta

    Yu, Hua-Gen

    2015-01-28

    We report a rigorous full dimensional quantum dynamics algorithm, the multi-layer Lanczos method, for computing vibrational energies and dipole transition intensities of polyatomic molecules without any dynamics approximation. The multi-layer Lanczos method is developed by using a few advanced techniques including the guided spectral transform Lanczos method, multi-layer Lanczos iteration approach, recursive residue generation method, and dipole-wavefunction contraction. The quantum molecular Hamiltonian at the total angular momentum J = 0 is represented in a set of orthogonal polyspherical coordinates so that the large amplitude motions of vibrations are naturally described. In particular, the algorithm is general and problem-independent. An applicationmore »is illustrated by calculating the infrared vibrational dipole transition spectrum of CH? based on the ab initio T8 potential energy surface of Schwenke and Partridge and the low-order truncated ab initio dipole moment surfaces of Yurchenko and co-workers. A comparison with experiments is made. The algorithm is also applicable for Raman polarizability active spectra.« less

  8. Multi-layer Lanczos iteration approach to calculations of vibrational energies and dipole transition intensities for polyatomic molecules

    DOE PAGESBeta

    Yu, Hua-Gen [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-01-28

    We report a rigorous full dimensional quantum dynamics algorithm, the multi-layer Lanczos method, for computing vibrational energies and dipole transition intensities of polyatomic molecules without any dynamics approximation. The multi-layer Lanczos method is developed by using a few advanced techniques including the guided spectral transform Lanczos method, multi-layer Lanczos iteration approach, recursive residue generation method, and dipole-wavefunction contraction. The quantum molecular Hamiltonian at the total angular momentum J = 0 is represented in a set of orthogonal polyspherical coordinates so that the large amplitude motions of vibrations are naturally described. In particular, the algorithm is general and problem-independent. An application is illustrated by calculating the infrared vibrational dipole transition spectrum of CH? based on the ab initio T8 potential energy surface of Schwenke and Partridge and the low-order truncated ab initio dipole moment surfaces of Yurchenko and co-workers. A comparison with experiments is made. The algorithm is also applicable for Raman polarizability active spectra.

  9. An accurate {ital ab initio} HOCl potential energy surface, vibrational and rotational calculations, and comparison with experiment

    SciTech Connect

    Skokov, S. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Altanta, Georgia 30322 (United States)] [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Altanta, Georgia 30322 (United States); Peterson, K.A. [Department of Chemistry, Washington State University and the Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)] [Department of Chemistry, Washington State University and the Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Bowman, J.M. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)] [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)

    1998-08-01

    Accurate {ital ab initio} multireference configuration interaction (CI) calculations with large correlation-consistent basis sets are performed for HOCl. After extrapolation to the complete basis set limit, the {ital ab initio} data are precisely fit to give a semiglobal three-dimensional potential energy surface to describe HOCl{r_arrow}Cl+OH from high overtone excitation of the OH-stretch. The average absolute deviation between the {ital ab initio} and fitted energies is 4.2thinspcm{sup {minus}1} for energies up to 60 kcal/mol relative to the HOCl minimum. Vibrational energies of HOCl including the six overtones of the OH-stretch are computed using a vibrational-Cl method on the fitted potential and also on a slightly adjusted potential. Near-spectroscopic accuracy is obtained using the adjusted potential; the average absolute deviation between theory and experiment for 19 experimentally reported states is 4.8thinspcm{sup {minus}1}. Very good agreement with experiment is also obtained for numerous rotational energies for the ground vibrational state, the ClO-stretch fundamental, and the fifth overtone of the OH-stretch. {copyright} {ital 1998 American Institute of Physics.}

  10. Crystal structure, vibrational studies, optical properties and DFT calculations of 2-amino-5-diethyl-aminopentanium tetrachlorocadmate (II)

    NASA Astrophysics Data System (ADS)

    Baklouti, Yosra; chaari, Najla; Feki, Habib; Chniba-Boudjada, Nassira; Zouari, Fatma

    2015-02-01

    Single crystals of a new organic-inorganic compound (C9H24N2) CdCl4 were grown by the slow evaporation technique and characterized by X-ray diffraction, infrared absorption Raman spectroscopy scattering, optical absorption, differential scanning calorimetry (DSC) analysis and dielectric measurements. The title compound belongs to the orthorhombic space group Pbca with the following unit cell parameters: a = 11.397(7), b = 13.843(4), c = 22.678(5) Å and Z = 8. In crystal structure, the tetrachlorocadmate anion is connected to organic cations through Nsbnd H⋯Cl hydrogen bonds. Theoretical calculations were performed using density functional theory (DFT) with the B3LYP/LanL2DZ level of theory for studying the molecular structure and vibrational spectra of the title compound. Good consistency is found between the calculated results and the experimental structure, IR, and Raman spectra. The detailed interpretation of the vibrational modes was carried out on the basis on our DFT calculations as primary source of assignment and by comparison with spectroscopic studies of similar compounds. The optical properties were investigated by optical absorption and show three bands at 300, 329 and 513 nm.

  11. Crystal structure, vibrational studies, optical properties and DFT calculations of 2-amino-5-diethyl-aminopentanium tetrachlorocadmate (II).

    PubMed

    Baklouti, Yosra; chaari, Najla; Feki, Habib; Chniba-Boudjada, Nassira; Zouari, Fatma

    2015-02-01

    Single crystals of a new organic-inorganic compound (C9H24N2) CdCl4 were grown by the slow evaporation technique and characterized by X-ray diffraction, infrared absorption Raman spectroscopy scattering, optical absorption, differential scanning calorimetry (DSC) analysis and dielectric measurements. The title compound belongs to the orthorhombic space group Pbca with the following unit cell parameters: a=11.397(7), b=13.843(4), c=22.678(5)Å and Z=8. In crystal structure, the tetrachlorocadmate anion is connected to organic cations through N-H?Cl hydrogen bonds. Theoretical calculations were performed using density functional theory (DFT) with the B3LYP/LanL2DZ level of theory for studying the molecular structure and vibrational spectra of the title compound. Good consistency is found between the calculated results and the experimental structure, IR, and Raman spectra. The detailed interpretation of the vibrational modes was carried out on the basis on our DFT calculations as primary source of assignment and by comparison with spectroscopic studies of similar compounds. The optical properties were investigated by optical absorption and show three bands at 300, 329 and 513 nm. PMID:25311521

  12. Calculation of rotational-vibrational preionization in H2 by multichannel quantum defect theory

    NASA Astrophysics Data System (ADS)

    Jungen, Ch.; Dill, Dan

    1980-10-01

    Multichannel quantum defect theory is adapted to treat simultaneous rotational and vibrational preionization in H2. The strongly preionized spectrum between the N+=0 and N+=2 rotational thresholds of photoionization of H2X1?g+(J?=0, v?=0) to produce H2+X2?g+(N+, v+=0) is computed as example and good agreement is obtained with the photoionization data of Dehmer and Chupka.

  13. Quantum-Chemical Calculation and Visualization of the Vibrational Modes of Graphene in Different Points of the Brillouin Zone.

    PubMed

    Lebedieva, Tetiana; Gubanov, Victor; Dovbeshko, Galyna; Pidhirnyi, Denys

    2015-12-01

    Different notations of graphene irreducible representations and optical modes could be found in the literature. The goals of this paper are to identify the correspondence between available notations, to calculate the optical modes of graphene in different points of the Brillouin zone, and to compare them with experimental data obtained by Raman and coherent anti-Stokes Raman scattering (CARS) spectroscopy. The mechanism of the resonance enhancement of vibration modes of the molecules adsorbed on graphene in CARS experiments is proposed. The possibility of appearance of the discrete breathing modes is discussed. PMID:26168865

  14. Influence of intramolecular vibrations in third-order, time-domain resonant spectroscopies. II. Numerical calculations

    NASA Astrophysics Data System (ADS)

    Ohta, Kaoru; Larsen, Delmar S.; Yang, Mino; Fleming, Graham R.

    2001-05-01

    We model recent experimental wavelength dependent Three Pulse Photon Echo Peak Shift (WD-3PEPS) and Transient Grating (WD-TG) signals considering both solvation dynamics and vibrational contributions. We present numerical simulations of WD-3PEPS and WD-TG signals of two probe molecules: Nile Blue and N,N-bisdimethylphenyl-2,4,6,8-perylenetetracarbonyl diamide to investigate the influence of intramolecular vibrations in the signals. By varying the excitation wavelength, we show that the different initial conditions for the vibrational wave packets significantly affect the signals, especially through the contributions associated with high frequency modes, often neglected in experimental analyses. We show that the temporal properties of both WD-TG and WD-3PEPS signals display sensitivities to both the excitation wavelength and the vibronic structure of the specific probe molecule used. Several mechanisms for generating vibronic modulations in the signals are discussed and their effects on the signals are described. Quantitative agreement between experiment and simulated signals requires accurate characterization of the laser pulses, specifically the magnitude and sign of chirp has a significant effect on the initial temporal properties of the signals. We provide a description of the experimental considerations required for accurate determination of molecular dynamics from 3PEPS and TG experiments and conclude with a brief discussion of the implications of our results for previous analyses of such experiments.

  15. A new treatment for predicting the self-excited vibrations of nonlinear systems with frictional interfaces: The Constrained Harmonic Balance Method, with application to disc brake squeal

    NASA Astrophysics Data System (ADS)

    Coudeyras, N.; Sinou, J.-J.; Nacivet, S.

    2009-01-01

    Brake squeal noise is still an issue since it generates high warranty costs for the automotive industry and irritation for customers. Key parameters must be known in order to reduce it. Stability analysis is a common method of studying nonlinear phenomena and has been widely used by the scientific and the engineering communities for solving disc brake squeal problems. This type of analysis provides areas of stability versus instability for driven parameters, thereby making it possible to define design criteria. Nevertheless, this technique does not permit obtaining the vibrating state of the brake system and nonlinear methods have to be employed. Temporal integration is a well-known method for computing the dynamic solution but as it is time consuming, nonlinear methods such as the Harmonic Balance Method (HBM) are preferred. This paper presents a novel nonlinear method called the Constrained Harmonic Balance Method (CHBM) that works for nonlinear systems subject to flutter instability. An additional constraint-based condition is proposed that omits the static equilibrium point (i.e. the trivial static solution of the nonlinear problem that would be obtained by applying the classical HBM) and therefore focuses on predicting both the Fourier coefficients and the fundamental frequency of the stationary nonlinear system. The effectiveness of the proposed nonlinear approach is illustrated by an analysis of disc brake squeal. The brake system under consideration is a reduced finite element model of a pad and a disc. Both stability and nonlinear analyses are performed and the results are compared with a classical variable order solver integration algorithm. Therefore, the objectives of the following paper are to present not only an extension of the HBM (CHBM) but also to demonstrate an application to the specific problem of disc brake squeal with extensively parametric studies that investigate the effects of the friction coefficient, piston pressure, nonlinear stiffness and structural damping.

  16. Structure and vibrational modes of AgI-doped AsSe glasses: Raman scattering and ab initio calculations

    SciTech Connect

    Kostadinova, O. [Foundation for Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes, P.O. Box 1414, Patras GR-26504 (Greece); Chrissanthopoulos, A. [Foundation for Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes, P.O. Box 1414, Patras GR-26504 (Greece); Department of Chemistry, University of Patras, Patras GR-26504 (Greece); Petkova, T. [Institute of Electrochemistry and Energy Systems (IEES), Bulgarian Academy of Sciences, Sofia (Bulgaria); Petkov, P. [Laboratory of Thin Film Technology, Department of Physics, University of Chemical Technology and Metallurgy, Sofia (Bulgaria); Yannopoulos, S.N., E-mail: sny@iceht.forth.g [Foundation for Research and Technology Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes, P.O. Box 1414, Patras GR-26504 (Greece)

    2011-02-15

    We report an investigation of the structure and vibrational modes of (AgI){sub x} (AsSe){sub 100-x}, bulk glasses using Raman spectroscopy and first principles calculations. The short- and medium-range structural order of the glasses was elucidated by analyzing the reduced Raman spectra, recorded at off-resonance conditions. Three distinct local environments were revealed for the AsSe glass including stoichiometric-like and As-rich network sub-structures, and cage-like molecules (As{sub 4}Se{sub n}, n=3, 4) decoupled from the network. To facilitate the interpretation of the Raman spectra ab initio calculations are employed to study the geometric and vibrational properties of As{sub 4}Se{sub n} molecular units that are parts of the glass structure. The incorporation of AgI causes appreciable structural changes into the glass structure. AgI is responsible for the population reduction of molecular units and for the degradation of the As-rich network-like sub-structure via the introduction of As-I terminal bonds. Ab initio calculations of mixed chalcohalide pyramids AsSe{sub m}I{sub 3-m} provided useful information augmenting the interpretation of the Raman spectra. -- Graphical abstract: Raman scattering and ab initio calculations are employed to study the structure of AgI-AsSe superionic glasses. The role of mixed chalcohalide pyramidal units as illustrated in the figure is elucidated. Display Omitted Research highlights: {yields} Doping binary As-Se glasses with AgI cause dramatic changes in glass structure. {yields} Raman scattering and ab initio calculations determine changes in short- and medium-range order. {yields} Three local environments exist in AsSe glass including a network sub-structure and cage-like molecules. {yields} Mixed chalcohalide pyramids AsSe{sub m}I{sub 3-m} dominate the AgI-doped glass structure.

  17. Integral transforms and the symmetry group of the harmonic oscillator, SU/sub 3/, as a tool for resonating group calculations

    SciTech Connect

    Zahn, W.

    1981-03-15

    Harmonic oscillator functions are widely used in modern low-energy physics, in general, and in refined resonating group calculations, in particular/sup 1/). Classification of the resonating group wave functions with respect to SU/sub 3/ has been proposed some years ago and implemented in great detail since then./sup 2/)/sup 3/)/sup 3/).

  18. Comparison of DFT with Traditional Methods for the Calculation of Vibrational Frequencies and Bond Energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

    1997-01-01

    The vibrational frequencies of MO2 are computed at many levels of theory, including HF, B3LYP, BP86, CASSCF, MP2, and CCSD(T). The computed results are compared with the available experimental results. Most of the methods fail for at least one state of the systems considered. The accuracy of the results and the origin of the observed failures are discussed. The B3LYP bond energies are compared with traditional methods for a variety of systems, ranging from FeCOn+ to SiCln and its positive ions. The cases where B3LYP differs from the traditional methods are discussed.

  19. Ab initio molecular dynamics with noisy and cheap quantum Monte Carlo forces: accurate calculation of vibrational frequencies

    NASA Astrophysics Data System (ADS)

    Luo, Ye; Sorella, Sandro

    2014-03-01

    We introduce a general and efficient method for the calculation of vibrational frequencies of electronic systems, ranging from molecules to solids. By performing damped molecular dynamics with ab initio forces, we show that quantum vibrational frequencies can be evaluated by diagonalizing the time averaged position-position or force-force correlation matrices, although the ionic motion is treated on the classical level within the Born-Oppenheimer approximation. The novelty of our approach is to evaluate atomic forces with QMC by means of a highly accurate and correlated variational wave function which is optimized simultaneously during the dynamics. QMC is an accurate and promising many-body technique for electronic structure calculation thanks to massively parallel computers. However, since infinite statistics is not feasible, property evaluation may be affected by large noise that is difficult to harness. Our approach controls the QMC stochastic bias systematically and gives very accurate results with moderate computational effort, namely even with noisy forces. We prove the accuracy and efficiency of our method on the water monomer[A. Zen et al., JCTC 9 (2013) 4332] and dimer. We are currently working on the challenging problem of simulating liquid water at ambient conditions.

  20. Molecular structure and vibrational analysis of Trifluoperazine by FT-IR, FT-Raman and UV-Vis spectroscopies combined with DFT calculations

    NASA Astrophysics Data System (ADS)

    Rajesh, P.; Gunasekaran, S.; Gnanasambandan, T.; Seshadri, S.

    2015-02-01

    The complete vibrational assignment and analysis of the fundamental vibrational modes of Trifluoperazine (TFZ) was carried out using the experimental FT-IR, FT-Raman and UV-Vis data and quantum chemical studies. The observed vibrational data were compared with the wavenumbers derived theoretically for the optimized geometry of the compound from the DFT-B3LYP gradient calculations employing 6-31G (d,p) basis set. Thermodynamic properties like entropy, heat capacity and enthalpy have been calculated for the molecule. The HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using natural bond orbital (NBO) and natural localized molecular orbital (NLMO) analysis. Important non-linear properties such as first hyperpolarizability of TFZ have been computed using B3LYP quantum chemical calculation.

  1. Image resolution limits resulting from mechanical vibrations. Part IV: real-time numerical calculation of optical transfer functions and experimental verification

    Microsoft Academic Search

    Ofer Hadar; Itai Dror; Norman S. Kopeika

    1994-01-01

    A method of calculating numerically the optical transfer function appropriate to any type of image motion and vibration, including random ones, has been developed. We compare the numerical calculation method to the experimental measurement; the close agreement justifies implementation in image restoration for blurring from any type of image motion. In addition, statistics regarding the limitation of resolution as a

  2. Infrared and Raman spectra, conformational stability, ab initio calculations of structure, and vibrational assignment of 2-hexyne

    NASA Astrophysics Data System (ADS)

    Bell, Stephen; Zhu, Xiaodong; Guirgis, Gamil A.; Durig, James R.

    2002-10-01

    The infrared spectra (3500-50 cm -1) of the gas and solid and the Raman spectra (3500-50 cm -1) of the liquid and solid have been recorded for 2-hexyne, CH 3-C?C-CH 2CH 2CH 3. Variable temperature studies of the infrared spectrum (3500-400 cm -1) of 2-hexyne dissolved in liquid krypton have also been recorded. Utilizing four anti/ gauche conformer pairs, the anti( trans) conformer is found to be the lower energy form with an enthalpy difference of 74±8 cm -1 (0.88±0.10 kJ/mol) determined from krypton solutions over the temperature range -105 to -150 °C. At room temperature it is estimated that there is 42% of the anti conformer present. Equilibrium geometries and energies of the two conformers have been determined by ab initio (HF and MP2) and hybrid DFT (B3LYP) methods using a number of basis sets. Only the HF and DFT methods predict the anti conformer as the more stable form as found experimentally. A vibrational assignment is proposed based on the force constants, relative intensities, depolarization ratios from the ab initio and DFT calculations and on rotational band contours obtained using the calculated equilibrium geometries. From calculated energies it is shown that the CH 3 group exhibits almost completely free rotation which is in agreement with the observation of sub-band structure for the degenerate methyl vibrations from which values of the Coriolis coupling constants, ?, have been determined. The results are compared to similar properties of some corresponding molecules.

  3. Ab initio calculation of vibrational frequencies of clusters in As x S1-x glass and Raman spectra

    NASA Astrophysics Data System (ADS)

    Shrivastava, Keshav; Radhika Devi, V.; Abu Kassim, Hasan; Jalil, Ithnin Abdul; Yusof, Norhasliza

    2007-03-01

    We have used the density functional theory (DFT) to calculate the vibrational frequencies from first principles by making clusters of atoms on a high speed computer. We have made the clusters, AsS4, As2S3, As3S2, As4S, AsS7, As2S6,As3S5,As4S4,As5S3,As6S2, As7S, L-As4S3, CS-As4S,CS-AsS4,ES-As2S6(L=linear zig-zag, CS=corner sharing, ES=edge sharing) and optimized the bond lengths and angles for the minimum energy. The number of computed values of the vibrational frequencies are consistent with 3N-3, where N is the number of atoms in a cluster. All of the computed values are tabulated and compared with those found in the Raman spectra of AsxS1-x (x=0.35-0.45) glasses. The experimentally found modes at 183, 221, 355, 371 cm-1 are consistent with those calculated for chain mode-As4S3, As3S2, As2S6, AsS7. In the net work glass the frequencies found are, 195, 206, 227, 351, 369, 371, 388 cm-1 which are consistent with those calculated for, As7S, As5S3, As7S, As6S2, As5S3, AsS7 and As4S. We have previously interpreted the Raman spectra of GeSI galass by this method ,V.R. Devi, et al, J. Non Cryst. Solids 351,489-494(2005).

  4. Analysis of methods for calculating the transition frequencies of the torsional vibration of acrolein isomers in the ground ( S 0) electronic state

    NASA Astrophysics Data System (ADS)

    Koroleva, L. A.; Tyulin, V. I.; Matveev, V. K.; Pentin, Yu. A.

    2013-05-01

    B3LYP, MP2, CCSD(T), and MP4/MP2 in the 6-311G( d, p), 6-311++G( d, p), cc-pVTZ, aug-cc-pVTZ bases used to calculate the transition frequencies of torsional vibration of trans- and cis-isomers of acrolein in the ground electronic state ( S 0) are analyzed. It is found that for trans-isomers, all methods of calculation except for B3LYP in the cc-pVTZ basis yield good agreement between the calculated and experimental values. It is noted that for the cis-isomer of acrolein, no method of calculation confirms the experimental value of the frequency of torsional vibration (138 cm-1). It is shown that the calculated and experimental values for obertones at 273.0 cm-1 and other transitions of torsional vibration are different for this isomer in particular. However, it is established that in some calculation methods (B3LYP, MP2), the frequency of the torsional vibration of the cis-isomer coincides with another experimental value of this frequency (166.5 cm-1). It is concluded that in analyzing the vibrational structure of the UV spectrum, the calculated and experimental values of its obertone (331.3 cm-1) coincide, along with its frequency. It is also noted that the frequency of torsional vibration for the cis-isomer (166.5 cm-1) can also be found in other experimental works if we change the allocation of torsional transition 18{1/1}.

  5. Strength, hardness, and lattice vibrations of Z-carbon and W-carbon: First-principles calculations

    NASA Astrophysics Data System (ADS)

    Li, Zhiping; Gao, Faming; Xu, Ziming

    2012-04-01

    The strength, hardness, and lattice vibrations of two superhard carbon allotropies, Z-carbon and W-carbon are investigated by first-principles calculations. Phonon dispersion calculations indicate that Z-carbon and W-carbon are dynamically stable at least up to 300 GPa. The strength calculations reveal that the failure mode in Z-carbon is dominated by the tensile type, and the [010] direction is the weakest one. In W-carbon, the failure mode is dominated by the shear type, and the (101)[111¯] direction is the weakest one. Although the ideal strength of diamond is distinctly greater than that of Z-carbon and W-carbon, the tensile strength and shear strength for Z-carbon and W-carbon show much lower anisotropies than that of diamond. The hardness calculations indicate that the average hardness of Z-carbon is less than that of diamond but greater than that of the W-carbon, M-carbon, and body-centered-tetragonal-C4 carbon. The simulated Raman spectra show that the Ag modes at 1094 cm-1 for Z-carbon and 1109.7 cm-1 for W-carbon are in agreement with that of 1082 cm-1 observed in the experiment of cold-compressed graphite at 9.8 GPa.

  6. Anharmonic Wave Functions of Proteins: Quantum Self-Consistent Field Calculations of BPTI

    NASA Astrophysics Data System (ADS)

    Roitberg, Adrian; Gerber, R. Benny; Elber, Ron; Ratner, Mark A.

    1995-06-01

    The harmonic approximation for the potential energy of proteins is known to be inadequate for the calculation of many protein properties. To study the effect of anharmonic terms on protein vibrations, the anharmonic wave functions for the ground state and low-lying excited states of the bovine pancreatic trypsin inhibitor (BPTI) were calculated. The results suggest that anharmonic treatments are essential for protein vibrational spectroscopy. The calculation uses the vibrational self-consistent field approximation, which includes anharmonicity and interaction among modes in a mean-field sense. Properties obtained include the quantum coordinate fluctuations, zero-point energies, and the vibrational absorption spectrum.

  7. A FEM-based method using harmonic overtones to determine the effective elastic, dielectric, and piezoelectric parameters of freely vibrating thick piezoelectric disks.

    PubMed

    Jonsson, Ulf G; Andersson, Britt M; Lindahl, Olof A

    2013-01-01

    To gain an understanding of the electroelastic properties of tactile piezoelectric sensors used in the characterization of soft tissue, the frequency-dependent electric impedance response of thick piezoelectric disks has been calculated using finite element modeling. To fit the calculated to the measured response, a new method was developed using harmonic overtones for tuning of the calculated effective elastic, piezoelectric, and dielectric parameters. To validate the results, the impedance responses of 10 piezoelectric disks with diameter-to-thickness ratios of 20, 6, and 2 have been measured from 10 kHz to 5 MHz. A two-dimensional, general purpose finite element partial differential equation solver with adaptive meshing capability run in the frequency-stepped mode, was used. The equations and boundary conditions used by the solver are presented. Calculated and measured impedance responses are presented, and resonance frequencies have been compared in detail. The comparison shows excellent agreement, with average relative differences in frequency of 0.27%, 0.19%, and 0.54% for the samples with diameter-to-thickness ratios of 20, 6, and 2, respectively. The method of tuning the effective elastic, piezoelectric, and dielectric parameters is an important step toward a finite element model that describes the properties of tactile sensors in detail. PMID:23287929

  8. Vibrational Spectroscopy of the G, , ,C Base Pair: Experiment, Harmonic and Anharmonic Calculations, and the Nature of the Anharmonic Couplings

    E-print Network

    de Vries, Mattanjah S.

    of amino acid2 and peptide conformations3 and the exploration of nucleic acid base tautomerization in spectroscopic identification of biological conformers and their properties. The structure of nucleic acid ba

  9. IOS and ECS line coupling calculation for the CO-He system - Influence on the vibration-rotation band shapes

    NASA Technical Reports Server (NTRS)

    Boissoles, J.; Boulet, C.; Robert, D.; Green, S.

    1987-01-01

    Line coupling coefficients resulting from rotational excitation of CO perturbed by He are computed within the infinite order sudden approximation (IOSA) and within the energy corrected sudden approximation (ECSA). The influence of this line coupling on the 1-0 CO-He vibration-rotation band shape is then computed for the case of weakly overlapping lines in the 292-78 K temperature range. The IOS and ECS results differ only at 78 K by a weak amount at high frequencies. Comparison with an additive superposition of Lorentzian lines shows strong modifications in the troughs between the lines. These calculated modifications are in excellent quantitative agreement with recent experimental data for all the temperatures considered. The applicability of previous approaches to CO-He system, based on either the strong collision model or exponential energy gap law, is also discussed.

  10. Vibrational spectroscopic studies (FT-IR, FT-Raman, SERS) and quantum chemical calculations on cyclobenzaprinium salicylate.

    PubMed

    Mary, Y Shyma; Jojo, P J; Van Alsenoy, Christian; Kaur, Manpreet; Siddegowda, M S; Yathirajan, H S; Nogueira, Helena I S; Cruz, Sandra M A

    2014-01-01

    FT-IR, FT-Raman and surface enhanced Raman scattering spectra of cyclobenzaprinium salicylate were recorded and analyzed. The vibrational wavenumbers were examined theoretically using the Gaussian09 set of quantum chemistry codes, and the normal modes were assigned by potential energy distribution calculations. The downshift of the OH stretching frequency is due to strong hydrogen bonded system present in the title compound as given by XRD results. The presence of CH3, CH2 and CO2 modes in the SERS spectrum indicates the nearness of the methyl group to the metal surface which affects the orientation and metal molecule interaction. The presence of phenyl ring modes in the SERS spectrum indicates a tilted orientation with respect to the metal surface. The geometrical parameters of the title compound are in agreement with XRD results. A computation of the first hyperpolarizability indicates that the compound may be a good candidate as a NLO material. PMID:24200648

  11. Ab Initio Calculation of Accurate Vibrational Frequencies for Molecules of Interest in Atmospheric Chemistry

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Langhoff, Stephen R. (Technical Monitor)

    1996-01-01

    Due to advances in quantum mechanical methods over the last few years, it is now possible to determine ab initio potential energy surfaces in which fundamental vibrational frequencies are accurate to within +/- 8 cm(sup -1) on average, and molecular bond distances are accurate to within +/- 0.001-0.003 A, depending on the nature of the bond. That is, the potential energy surfaces have not been scaled or empirically adjusted in any way, showing that theoretical methods have progressed to the point of being useful in analyzing spectra that are not from a tightly controlled laboratory environment, such as rovibrational spectra from the interstellar medium. Some recent examples demonstrating this accuracy win be presented and discussed. These include the HNO, CH4, C2H4, and ClCN molecules. The HNO molecule is interesting due to the very large H-N anharmonicity, while ClCN has a very large Fermi resonance. The ab initio studies for the CH4 and C2H4 molecules present the first accurate full quartic force fields of any kind (i.e., whether theoretical or empirical) for a five-atom and six-atom system, respectively.

  12. Infrared and Raman spectra, conformational stability, normal coordinate analysis, ab initio calculations, and vibrational assignment of 1 methylsilacyclobutane

    NASA Astrophysics Data System (ADS)

    Durig, James R.; Yanping, Jin; Pengqian, Zhen; Gounev, Todor K.; Guirgis, Gamil A.

    1999-03-01

    The infrared (3500-40 cm -1) spectra of gaseous and solid 1-methylsilacyclobutane, c-C 3H 6SiH(CH 3), have been recorded. In addition, the Raman spectrum (3500-30 cm -1) of the liquid has also been recorded and quantitative depolarization values obtained. Both the axial and equatorial conformers, with respect to methyl group, have been identified in the fluid phases. Variable temperature studies (-55 to -100°C) of the infrared spectra of the sample dissolved in liquid xenon have been carried out. From these data, the enthalpy difference has been determined to be 122±26 cm -1 (1.46±0.32 kJ/mol), with the equatorial conformer being the more stable structure. However, with repeated annealing of the amorphous solid, it was not possible to obtain a polycrystalline solid with a single conformer. A complete vibrational assignment is proposed for the equatorial conformer based on infrared band contours, relative intensities, depolarization values and group frequencies. Most of the fundamentals for the axial conformer have also been identified. Utilizing the frequency of the silicon-hydrogen (Si-H) stretching mode, the Si-H distance has been determined to be 1.490 Å for both conformers. The vibrational assignments are supported by normal coordinate calculations utilizing ab initio force constants. Complete equilibrium geometries have been determined for both rotamers by ab initio calculations, employing the 3-21G* and 6-31G* basis sets at the levels of restricted Hartree-Fock (RHF) and/or Moller-Plesset (MP) to second order. The results are discussed and compared with those obtained for some similar molecules.

  13. Calculation of Dynamic Loads Due to Random Vibration Environments in Rocket Engine Systems

    NASA Technical Reports Server (NTRS)

    Christensen, Eric R.; Brown, Andrew M.; Frady, Greg P.

    2007-01-01

    An important part of rocket engine design is the calculation of random dynamic loads resulting from internal engine "self-induced" sources. These loads are random in nature and can greatly influence the weight of many engine components. Several methodologies for calculating random loads are discussed and then compared to test results using a dynamic testbed consisting of a 60K thrust engine. The engine was tested in a free-free condition with known random force inputs from shakers attached to three locations near the main noise sources on the engine. Accelerations and strains were measured at several critical locations on the engines and then compared to the analytical results using two different random response methodologies.

  14. Dissociative recombination and vibrational excitation of CO+: model calculations and comparison with experiment

    NASA Astrophysics Data System (ADS)

    Mezei, J. Zs; Backodissa-Kiminou, R. D.; Tudorache, D. E.; Morel, V.; Chakrabarti, K.; Motapon, O.; Dulieu, O.; Robert, J.; Tchang-Brillet, W.-Ü. L.; Bultel, A.; Urbain, X.; Tennyson, J.; Hassouni, K.; Schneider, I. F.

    2015-06-01

    The latest molecular data—potential energy curves and Rydberg/valence interactions—characterizing the super-excited electronic states of CO are reviewed, in order to provide inputs for the study of their fragmentation dynamics. Starting from this input, the main paths and mechanisms for CO+ dissociative recombination are analyzed; its cross sections are computed using a method based on multichannel quantum defect theory. Convoluted cross sections, giving both isotropic and anisotropic Maxwellian rate coefficients, are compared with merged-beam and storage-ring experimental results. The calculated cross sections underestimate the measured ones by a factor of two, but display a very similar resonant shape. These facts confirm the quality of our approach for the dynamics, and call for more accurate and more extensive molecular structure calculations.

  15. Experimental study on the structure and vibrational, thermal and dielectric properties of bis(2-methylanilinium) selenate accomplished with DFT calculation

    NASA Astrophysics Data System (ADS)

    Ben hassen, C.; Boujelbene, M.; Bahri, M.; Zouari, N.; Mhiri, T.

    2014-09-01

    The present paper undertakes the study of a new hybrid compound [2-CH3C6H4NH3]2SeO4 characterized by the X-ray diffraction, IR, DFT calculation, TG-DTA, DSC and electrical conductivity. This new organic-inorganic hybrid compound crystallizes in the monoclinic system with P21/c space group and the following parameters a = 14.821 (5) Å; b = 16.245 (5) Å; c = 6.713 (5) Å; ß = 102.844 (5)°, Z = 4 and V = 1575.8 (14) Å3. The atomic arrangement can be described as isolated tetrahedral SeO42- connected with the organic groups by means of Nsbnd H⋯O hydrogen bonds to form infinite sinusoidal chains in the c-direction. BHHLYP/6-311g** method was used to determine the harmonic frequencies for two optimized cluster structures. The calculated modes were animated using the Molden graphical package to give tentative assignments of the observed IR spectra. Thermal analysis of the title compound does not indicate the occurrence of a phase transition in the temperature range of 300-650 K. Dielectric study of this compound has been measured, in order to determine the conductivity. The conductivity relaxation parameters associated with some H+ conduction have been determined from an analysis of the M?/M?max spectrum measured in a wide temperature range.

  16. Storage capacity and vibration frequencies of guest molecules in CH4 and CO2 hydrates by first-principles calculations.

    PubMed

    Cao, Xiaoxiao; Su, Yan; Liu, Yuan; Zhao, Jijun; Liu, Changling

    2014-01-01

    Using first-principle calculations at B97-D/6-311++G(2d,2p) level, we systematically explore the gas capacity of five standard water cavities (5(12), 4(3)5(6)6(3), 5(12)6(2), 5(12)6(4), and 5(12)6(8)) in clathrate hydrate and study the inclusion complexes to infer general trends in vibrational frequencies of guest molecules as a function of cage size and number of guest molecules. In addition, the Raman spectra of hydrates from CO2/CH4 gases are simulated. From our calculations, the maximum cage occupancy of the five considered cages (5(12), 4(3)5(6)6(3), 5(12)6(2), 5(12)6(4), and 5(12)6(8)) is one, one, two, three, and seven for both CH4 and CO2 guest molecules, respectively. Meanwhile, the optimum cage occupancy are one, one, one, two, and four for CO2 molecules and one, one, two, three, and five for CH4 molecules, respectively. Both the C-H stretching frequency of CH4 and the C-O stretching frequency of CO2 gradually decrease as size of the water cages increases. Meanwhile, the C-H stretching frequency gradually increases as the amount of CH4 molecules in the water cavity (e.g., 5(12)6(8)) increases. PMID:24320601

  17. Molecular vibrations and rotations Prof. dr. Ad van der Avoird

    E-print Network

    forces ("force field") associated with chemical bonds spectra of van der Waals molecules intermolecular (noncovalent) forces 0.3 Vibrations of polyatomic molecules (harmonic) 0.3.1 Harmonic oscillator in one . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 0.3 Vibrations of polyatomic molecules (harmonic) . . . . . . . . . 3 0.3.1 Harmonic oscillator

  18. MORSMATEL: a rapid and efficient code to calculate vibration-rotational matrix elements for r-dependent operators of two Morse oscillators

    NASA Astrophysics Data System (ADS)

    Lopez-Piñeiro, A.; Sanchez, M. L.; Moreno, B.

    1992-06-01

    The computer program MORSMATEL has been developed to calculate vibrational-rotational matrix elements of several r-dependent operators of two Morse oscillators. This code is based on a set of recurrence relations which are valid for any value of the power and of the quantum numbers v and J of each oscillator.

  19. Vibrational Spectra, Theoretical Calculations, and Structures of Cyclic Silanes, 2,4,7-Trioxa(3.3.0)Octane and Botryococcenes 

    E-print Network

    Chun, Hye Jin

    2014-12-08

    of the twist minima. The vibrational assignments of 2,4,7-trioxa(3.3.0)octane have been made based on its infrared and Raman spectra and theoretical DFT calculations. The two ring-puckering motions (in-phase and out-of-phase) were observed in the Raman spectrum...

  20. P1F-3 Numerically-Analytical Calculation Method for Vibration Amplitude Distributions of Inharmonic Modes of Double Rotated Cuts Thickness-Shear Resonators

    Microsoft Academic Search

    Aleksandr N. Lepetaev; Igor V. Khomenko; Anatoly V. Kosykh

    2007-01-01

    The article contains the information about numerically- analytical solution of model of SC-quartz resonator. The article presents formation of analytical model and shows results of the solution by means of numerical method. Pictures of vibration amplitude distribution are showed on figures. Results of calculations are being compared with the measured data. Example of application is showed in the article.

  1. Molecular conformational analysis, vibrational spectra and normal coordinate analysis of trans-1,2-bis(3,5-dimethoxy phenyl)-ethene based on density functional theory calculations

    NASA Astrophysics Data System (ADS)

    Joseph, Lynnette; Sajan, D.; Chaitanya, K.; Isac, Jayakumary

    2014-03-01

    The conformational behavior and structural stability of trans-1,2-bis(3,5-dimethoxy phenyl)-ethene (TDBE) were investigated by using density functional theory (DFT) method with the B3LYP/6-311++G(d,p) basis set combination. The vibrational wavenumbers of TDBE were computed at DFT level and complete vibrational assignments were made on the basis of normal coordinate analysis calculations (NCA). The DFT force field transformed to natural internal coordinates was corrected by a well-established set of scale factors that were found to be transferable to the title compound. The infrared and Raman spectra were also predicted from the calculated intensities. The observed Fourier transform infrared (FTIR) and Fourier transform (FT) Raman vibrational wavenumbers were analyzed and compared with the theoretically predicted vibrational spectra. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP).

  2. Time-resolved dynamics in N2O4 probed using high harmonic generation.

    PubMed

    Li, Wen; Zhou, Xibin; Lock, Robynne; Patchkovskii, Serguei; Stolow, Albert; Kapteyn, Henry C; Murnane, Margaret M

    2008-11-21

    The attosecond time-scale electron-recollision process that underlies high harmonic generation has uncovered extremely rapid electronic dynamics in atoms and diatomics. We showed that high harmonic generation can reveal coupled electronic and nuclear dynamics in polyatomic molecules. By exciting large amplitude vibrations in dinitrogen tetraoxide, we showed that tunnel ionization accesses the ground state of the ion at the outer turning point of the vibration but populates the first excited state at the inner turning point. This state-switching mechanism is manifested as bursts of high harmonic light that is emitted mostly at the outer turning point. Theoretical calculations attribute the large modulation to suppressed emission from the first excited state of the ion. More broadly, these results show that high harmonic generation and strong-field ionization in polyatomic molecules undergoing bonding or configurational changes involve the participation of multiple molecular orbitals. PMID:18974317

  3. Analysis of ?-PHASE Rdx Vibrational Lattice Modes Under Hydrostatic Pressur

    NASA Astrophysics Data System (ADS)

    Slough, W. J.; Perger, W. F.

    2009-12-01

    Calculations using the all-electron CRYSTAL06 program employing density functional theory are used to calculate the terahertz vibrational frequencies of ?-phase RDX. The lowest frequency infrared active lattice modes are investigated as a function of hydrostatic pressure from ambient conditions up to 3 GPa. A given mode may be composed of both external and internal vibration contributions, with the composition changing as a function of pressure. The anharmonic deviation of each mode from simple harmonic behavior as a function of pressure is also explored.

  4. Ion-orbital coupling in Car-Parrinello calculations of hydrogen-bond vibrational dynamics: Case study with the NH3-HCl dimer

    NASA Astrophysics Data System (ADS)

    Ong, S. W.; Lee, B. X. B.; Kang, H. C.

    2011-09-01

    We have performed Car-Parrinello molecular dynamics (CPMD) calculations of the hydrogen-bonded NH3-HCl dimer. Our main aim is to establish how ionic-orbital coupling in CPMD affects the vibrational dynamics in hydrogen-bonded systems by characterizing the dependence of the calculated vibrational frequencies upon the orbital mass in the adiabatic limit of Car-Parrinello calculations. We use the example of the NH3-HCl dimer because of interest in its vibrational spectrum, in particular the magnitude of the frequency shift of the H-Cl stretch due to the anharmonic interactions when the hydrogen bond is formed. We find that an orbital mass of about 100 a.u. or smaller is required in order for the ion-orbital coupling to be linear in orbital mass, and the results for which can be accurately extrapolated to the adiabatic limit of zero orbital mass. We argue that this is general for hydrogen-bonded systems, suggesting that typical orbital mass values used in CPMD are too high to accurately describe vibrational dynamics in hydrogen-bonded systems. Our results also show that the usual application of a scaling factor to the CPMD frequencies to correct for the effects of orbital mass is not valid. For the dynamics of the dimer, we find that the H-Cl stretch and the N-H-Cl bend are significantly coupled, suggesting that it is important to include the latter degree of freedom in quantum dynamical calculations. Results from our calculations with deuterium-substitution show that both these degrees of freedom have significant anharmonic interactions. Our calculated frequency for the H-Cl stretch using the Becke-exchange Lee-Yang-Parr correlation functional compares reasonably well with a previous second-order Møller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix.

  5. Ion-orbital coupling in Car-Parrinello calculations of hydrogen-bond vibrational dynamics: case study with the NH3-HCl dimer.

    PubMed

    Ong, S W; Lee, B X B; Kang, H C

    2011-09-14

    We have performed Car-Parrinello molecular dynamics (CPMD) calculations of the hydrogen-bonded NH(3)-HCl dimer. Our main aim is to establish how ionic-orbital coupling in CPMD affects the vibrational dynamics in hydrogen-bonded systems by characterizing the dependence of the calculated vibrational frequencies upon the orbital mass in the adiabatic limit of Car-Parrinello calculations. We use the example of the NH(3)-HCl dimer because of interest in its vibrational spectrum, in particular the magnitude of the frequency shift of the H-Cl stretch due to the anharmonic interactions when the hydrogen bond is formed. We find that an orbital mass of about 100 a.u. or smaller is required in order for the ion-orbital coupling to be linear in orbital mass, and the results for which can be accurately extrapolated to the adiabatic limit of zero orbital mass. We argue that this is general for hydrogen-bonded systems, suggesting that typical orbital mass values used in CPMD are too high to accurately describe vibrational dynamics in hydrogen-bonded systems. Our results also show that the usual application of a scaling factor to the CPMD frequencies to correct for the effects of orbital mass is not valid. For the dynamics of the dimer, we find that the H-Cl stretch and the N-H-Cl bend are significantly coupled, suggesting that it is important to include the latter degree of freedom in quantum dynamical calculations. Results from our calculations with deuterium-substitution show that both these degrees of freedom have significant anharmonic interactions. Our calculated frequency for the H-Cl stretch using the Becke-exchange Lee-Yang-Parr correlation functional compares reasonably well with a previous second-order Møller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix. PMID:21932876

  6. First-principle calculation and assignment for vibrational spectra of Ba(Mg1/3Nb2/3)O3 microwave dielectric ceramic

    NASA Astrophysics Data System (ADS)

    Diao, Chuan-Ling; Wang, Chun-Hai; Luo, Neng-Neng; Qi, Ze-Ming; Shao, Tao; Wang, Yu-Yin; Lu, Jing; Wang, Quan-Chao; Kuang, Xiao-Jun; Fang, Liang; Shi, Feng; Jing, Xi-Ping

    2014-03-01

    1:2 B-site cation ordered Ba(Mg1/3Nb2/3)O3 ceramic was synthesized using conventional solid-state reaction at 1600 °C for 12 h. The structure parameters were obtained through Rietveld refinement of X-ray diffraction data. The Raman peak frequencies were obtained by Lorenz fitting on Raman spectrum. Four-parameter semiquantum model was used to fit the infrared (IR) reflectivity spectrum, and the fitted parameters were used to calculate the dielectric permittivity ? and dielectric loss tan?. A total of 9 active Raman and 16 active IR modes were obtained using first-principle calculations based on density functional theory with local density approximation. All of the vibrational modes were assigned and represented by linear combinations of the symmetry coordinates deduced using group theory analysis. The Raman mode with the highest frequency A1g(4) (789 cm-1) can be described as the breathing vibration of NbO6. The IR modes Eu(1) (149 cm-1) and A2u(2) (212 cm-1), which can be described as the twisting vibrations of Ba-MgO6/Ba-NbO6 on the a-b plane and the stretching vibrations of Ba-MgO6/Ba-NbO6 along the c direction, respectively, are the dominant contributing modes to ? and tan?. The dielectric property parameters obtained using IR spectrum fittings, first-principal calculations, and microwave measurements were compared.

  7. Scaling factors for fundamental vibrational frequencies and zero-point energies obtained from HF, MP2, and DFT\\/DZP and TZP harmonic frequencies

    Microsoft Academic Search

    S. G. Andrade; Luísa C. S. Gonçalves; F. E. Jorge

    2008-01-01

    Recently, segmented contracted basis sets of double, triple, and quadruple zeta valence quality plus polarization functions (XZP, X=D, T, and Q) for the atoms from H to Ar were presented by Jorge et al. Scaling factors for the fundamental vibrational frequencies, low-frequency vibrations, and zero-point vibrational energies (ZPVEs) evaluated at 14 levels of theory are reported. The ab initio Hartree–Fock

  8. Quantum mechanical calculations of vibrational population inversion in chemical reactions - Numerically exact L-squared-amplitude-density study of the H2Br reactive system

    NASA Technical Reports Server (NTRS)

    Zhang, Y. C.; Zhang, J. Z. H.; Kouri, D. J.; Haug, K.; Schwenke, D. W.

    1988-01-01

    Numerically exact, fully three-dimensional quantum mechanicl reactive scattering calculations are reported for the H2Br system. Both the exchange (H + H-prime Br to H-prime + HBr) and abstraction (H + HBR to H2 + Br) reaction channels are included in the calculations. The present results are the first completely converged three-dimensional quantum calculations for a system involving a highly exoergic reaction channel (the abstraction process). It is found that the production of vibrationally hot H2 in the abstraction reaction, and hence the extent of population inversion in the products, is a sensitive function of initial HBr rotational state and collision energy.

  9. Harmonic Analysis

    Microsoft Academic Search

    Vladimir I Clue; William Kelleher; Anatoly Levin

    2005-01-01

    This paper describes a method of calculating the transforms, currently\\u000aobtained via Fourier and reverse Fourier transforms. The method allows\\u000acalculating efficiently the transforms of a signal having an arbitrary\\u000adimension of the digital representation by reducing the transform to a\\u000avector-to-circulant matrix multiplying. There is a connection between harmonic\\u000aequations in rectangular and polar coordinate systems. The connection\\u000aestablished

  10. Simple systematization of vibrational excitation cross-section calculations for resonant electron-molecule scattering in the boomerang and impulse models.

    PubMed

    Sarma, Manabendra; Adhikari, S; Mishra, Manoj K

    2007-01-28

    Vibrational excitation (nu(f)<--nu(i)) cross-sections sigma(nu(f)<--nu(i) )(E) in resonant e-N(2) and e-H(2) scattering are calculated from transition matrix elements T(nu(f),nu(i) )(E) obtained using Fourier transform of the cross correlation function , where psi(nu(i))(R,t) approximately =e(-iH(A(2))-(R)t/h phi(nu(i))(R) with time evolution under the influence of the resonance anionic Hamiltonian H(A(2) (-))(A(2) (-)=N(2)(-)/H(2) (-)) implemented using Lanczos and fast Fourier transforms. The target (A(2)) vibrational eigenfunctions phi(nu(i))(R) and phi(nu(f))(R) are calculated using Fourier grid Hamiltonian method applied to potential energy (PE) curves of the neutral target. Application of this simple systematization to calculate vibrational structure in e-N(2) and e-H(2) scattering cross-sections provides mechanistic insights into features underlying presence/absence of structure in e-N(2) and e-H(2) scattering cross-sections. The results obtained with approximate PE curves are in reasonable agreement with experimental/calculated cross-section profiles, and cross correlation functions provide a simple demarcation between the boomerang and impulse models. PMID:17286472

  11. Simple systematization of vibrational excitation cross-section calculations for resonant electron-molecule scattering in the boomerang and impulse models

    NASA Astrophysics Data System (ADS)

    Sarma, Manabendra; Adhikari, S.; Mishra, Manoj K.

    2007-01-01

    Vibrational excitation (?f??i) cross-sections ??f??i(E) in resonant e-N2 and e-H2 scattering are calculated from transition matrix elements T?f,?i(E ) obtained using Fourier transform of the cross correlation function ???f(R)???i(R,t)?, where ??i(R,t)?e-iHA2-(R)t/???i(R) with time evolution under the influence of the resonance anionic Hamiltonian HA2-(A2-=N2-/H2-) implemented using Lanczos and fast Fourier transforms. The target (A2) vibrational eigenfunctions ??i(R) and ??f(R) are calculated using Fourier grid Hamiltonian method applied to potential energy (PE) curves of the neutral target. Application of this simple systematization to calculate vibrational structure in e-N2 and e-H2 scattering cross-sections provides mechanistic insights into features underlying presence/absence of structure in e-N2 and e-H2 scattering cross-sections. The results obtained with approximate PE curves are in reasonable agreement with experimental/calculated cross-section profiles, and cross correlation functions provide a simple demarcation between the boomerang and impulse models.

  12. Anharmonic Vibrational Spectroscopy on Metal Transition Complexes

    NASA Astrophysics Data System (ADS)

    Latouche, Camille; Bloino, Julien; Barone, Vincenzo

    2014-06-01

    Advances in hardware performance and the availability of efficient and reliable computational models have made possible the application of computational spectroscopy to ever larger molecular systems. The systematic interpretation of experimental data and the full characterization of complex molecules can then be facilitated. Focusing on vibrational spectroscopy, several approaches have been proposed to simulate spectra beyond the double harmonic approximation, so that more details become available. However, a routine use of such tools requires the preliminary definition of a valid protocol with the most appropriate combination of electronic structure and nuclear calculation models. Several benchmark of anharmonic calculations frequency have been realized on organic molecules. Nevertheless, benchmarks of organometallics or inorganic metal complexes at this level are strongly lacking despite the interest of these systems due to their strong emission and vibrational properties. Herein we report the benchmark study realized with anharmonic calculations on simple metal complexes, along with some pilot applications on systems of direct technological or biological interest.

  13. Energy, contact, and density profiles of one-dimensional fermions in a harmonic trap via nonuniform-lattice Monte Carlo calculations

    NASA Astrophysics Data System (ADS)

    Berger, C. E.; Anderson, E. R.; Drut, J. E.

    2015-05-01

    We determine the ground-state energy and Tan's contact of attractively interacting few-fermion systems in a one-dimensional harmonic trap, for a range of couplings and particle numbers. Complementing those results, we show the corresponding density profiles. The calculations were performed with a lattice Monte Carlo approach based on a nonuniform discretization of space, defined via Gauss-Hermite quadrature points and weights. This particular coordinate basis is natural for systems in harmonic traps, and can be generalized to traps of other shapes. In all cases, it yields a position-dependent coupling and a corresponding nonuniform Hubbard-Stratonovich transformation. The resulting path integral is performed with hybrid Monte Carlo as a proof of principle for calculations at finite temperature and in higher dimensions. We present results for N =4 ,...,20 particles (although the method can be extended beyond that) to cover the range from few- to many-particle systems. This method is exact up to statistical and systematic uncertainties, which we account for—and thus also represents an ab initio calculation of this system, providing a benchmark for other methods and a prediction for ultracold-atom experiments.

  14. Faraday Discuss., 1994,99, 121-129 Basis Set Convergenceand Correlation Effects in Vibrational

    E-print Network

    Helgaker, Trygve

    . Introduction In the harmonic approximation, IR absorption intensities and vibrational circular dichroism (VCD, the atomic polar tensor (APT) and the atomic axial tensor (AAT).'*2 The AAT is needed only for VCD of basis set.6 Conse- quently, for the LAO method we should expect the calculated VCD spectra to converge

  15. Self-consistent multicomponent envelope function calculation of normal incidence second-harmonic generation in p-type doped symmetric quantum wells

    Microsoft Academic Search

    Ansheng Liu

    1997-01-01

    In a self-consistent multicomponent envelope function approach, we showed that ?xxx(2) component of the second-harmonic susceptibility tensor of a symmetric p-type quantum well (QW) exists, because of the valence-band mixing at nonzero values of the in-plane wave vector. For a highly doped narrow GaAs\\/Al0.3Ga0.7As QW, our calculation indicates that at low temperatures a large value (?10?7 m\\/V) of ?xxx(2) can

  16. Optimal geometries and harmonic vibrational frequencies of the global minima of water clusters (H2O)n, n=2-6, and several hexamer local minima at the CCSD(T) level of theory

    SciTech Connect

    Miliordos, Evangelos; Apra, Edoardo; Xantheas, Sotiris S.

    2013-09-21

    We report the first optimum geometries and harmonic vibrational frequencies for the ring pentamer and several water hexamer (prism, cage, cyclic and two book) at the CCSD(T)/aug-cc-pVDZ level of theory. All five hexamer isomer minima previously reported by MP2 are also minima on the CCSD(T) potential energy surface (PES). In addition, all CCSD(T) minimum energy structures for the n=2-6 cluster isomers are quite close to the ones previously obtained by MP2 on the respective PESs, as confirmed by a modified Procrustes analysis that quantifies the difference between any two cluster geometries. The CCSD(T) results confirm the cooperative effect of the homodromic ring networks (systematic contraction of the nearest-neighbor (nn) intermolecular separations with cluster size) previously reported by MP2, albeit with O-O distances shorter by ~0.02 Å, indicating that MP2 overcorrects this effect. The harmonic frequencies at the minimum geometries were obtained by the double differentiation of the CCSD(T) energy using an efficient scheme based on internal coordinates that reduces the number of required single point energy evaluations by ~15% when compared to the corresponding double differentiation using Cartesian coordinates. Negligible differences between MP2 and CCSD(T) are found for the librational modes, while uniform increases of ~15 and ~25 cm-1 are observed for the bending and “free” OH harmonic frequencies. The largest differences between MP2 and CCSD(T) are observed for the harmonic hydrogen bonded frequencies. The CCSD(T) red shifts from the monomer frequencies (??) are smaller than the MP2 ones, due to the fact that the former produces shorter elongations (?R) of the respective hydrogen bonded OH lengths from the monomer value with respect to the latter. Both the MP2 and CCSD(T) results for the hydrogen bonded frequencies were found to closely follow the relation - ?? = s ? ?R, with a rate of s = 20.3 cm-1 / 0.001 Å. The CCSD(T) harmonic frequencies, when corrected using the MP2 anharmonicities obtained from second order vibrational perturbation theory (VPT2), produce anharmonicCCSD(T) estimates that are within < 60 cm-1 from the measured infrared (IR) active bands of the n=2-6 clusters and furthermore trace the observed red shifts with respect to the monomer (??) quite accurately. The energetic order between the various hexamer isomers on the PES (prism has the lowest energy) previously reported at MP2 was found to be preserved at the CCSD(T) level, whereas the inclusion of anharmonic corrections further stabilizes the cage among the hexamer isomers.

  17. A formulation of rotor-airframe coupling for design analysis of vibrations of helicopter airframes

    NASA Technical Reports Server (NTRS)

    Kvaternik, R. G.; Walton, W. C., Jr.

    1982-01-01

    A linear formulation of rotor airframe coupling intended for vibration analysis in airframe structural design is presented. The airframe is represented by a finite element analysis model; the rotor is represented by a general set of linear differential equations with periodic coefficients; and the connections between the rotor and airframe are specified through general linear equations of constraint. Coupling equations are applied to the rotor and airframe equations to produce one set of linear differential equations governing vibrations of the combined rotor airframe system. These equations are solved by the harmonic balance method for the system steady state vibrations. A feature of the solution process is the representation of the airframe in terms of forced responses calculated at the rotor harmonics of interest. A method based on matrix partitioning is worked out for quick recalculations of vibrations in design studies when only relatively few airframe members are varied. All relations are presented in forms suitable for direct computer implementation.

  18. Vibrational spectroscopic and DFT calculation studies of 2-amino-7-bromo-5-oxo-[1]benzopyrano [2,3-b]pyridine-3 carbonitrile.

    PubMed

    Premkumar, S; Jawahar, A; Mathavan, T; Kumara Dhas, M; Milton Franklin Benial, A

    2015-03-01

    The vibrational spectra of 2-amino-7-bromo-5-oxo-[1]benzopyrano [2,3-b]pyridine-3 carbonitrile were recorded using fourier transform-infrared and fourier transform-Raman spectrometer. The optimized structural parameters, vibrational frequencies, Mulliken atomic charge distribution, frontier molecular orbitals, thermodynamic properties, temperature dependence of thermodynamic parameters, first order hyperpolarizability and natural bond orbital calculations of the molecule were performed using the Gaussian 09 program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program. The calculated first order hyperpolarizability of ABOBPC molecule was obtained as 6.908×10(-30) issue, which was 10.5 times greater than urea. The nonlinear optical activity of the molecule was also confirmed by the frontier molecular orbitals and natural bond orbital analysis. The frontier molecular orbitals analysis shows that the lower energy gap of the molecule, which leads to the higher value of first order hyperpolarizability. The natural bond orbital analysis indicates that the nonlinear optical activity of the molecule arises due to the ???(?) transitions. The Mulliken atomic charge distribution confirms the presence of intramolecular charge transfer within the molecule. The reactive site of the molecule was predicted from the molecular electrostatic potential contour map. The values of thermo dynamic parameters were increasing with increasing temperature. PMID:25498822

  19. Vibrational spectroscopic and DFT calculation studies of 2-amino-7-bromo-5-oxo-[1]benzopyrano [2,3-b]pyridine-3 carbonitrile

    NASA Astrophysics Data System (ADS)

    Premkumar, S.; Jawahar, A.; Mathavan, T.; Kumara Dhas, M.; Milton Franklin Benial, A.

    2015-03-01

    The vibrational spectra of 2-amino-7-bromo-5-oxo-[1]benzopyrano [2,3-b]pyridine-3 carbonitrile were recorded using fourier transform-infrared and fourier transform-Raman spectrometer. The optimized structural parameters, vibrational frequencies, Mulliken atomic charge distribution, frontier molecular orbitals, thermodynamic properties, temperature dependence of thermodynamic parameters, first order hyperpolarizability and natural bond orbital calculations of the molecule were performed using the Gaussian 09 program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program. The calculated first order hyperpolarizability of ABOBPC molecule was obtained as 6.908 × 10-30 issue, which was 10.5 times greater than urea. The nonlinear optical activity of the molecule was also confirmed by the frontier molecular orbitals and natural bond orbital analysis. The frontier molecular orbitals analysis shows that the lower energy gap of the molecule, which leads to the higher value of first order hyperpolarizability. The natural bond orbital analysis indicates that the nonlinear optical activity of the molecule arises due to the ? ? ?? transitions. The Mulliken atomic charge distribution confirms the presence of intramolecular charge transfer within the molecule. The reactive site of the molecule was predicted from the molecular electrostatic potential contour map. The values of thermo dynamic parameters were increasing with increasing temperature.

  20. Molecular structure, vibrational spectra, HOMO, LUMO and NMR studies of 2,3,4,5,6-penta bromo toluene and bromo durene based on density functional calculations.

    PubMed

    Krishna Kumar, V; Suganya, S; Mathammal, R

    2014-05-01

    This work deals with the vibrational spectra of 2,3,4,5,6-Penta Bromo Toluene (PBT) and Bromo Durene (BD) by quantum chemical calculations. The solid phase FTIR and FT-Raman spectra of the title compounds were recorded in the regions 4000-400 cm(-1) and 4000-50 cm(-1), respectively. The spectra were interpreted with the aid of normal coordinate analysis based on density functional theory (DFT) using B3LYP/6-31G* level and basis set combinations and was scaled using various scale factors yielding a good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. The HOMO and LUMO energies were calculated within the molecule. (13)C and (1)H NMR chemical shifts results were also calculated and compared with the experimental values. Thermodynamical properties like entropy heat capacity, zero point energy have been calculated for the title molecules. PMID:24556128

  1. Molecular structure, vibrational spectra, HOMO, LUMO and NMR studies of 2,3,4,5,6-Penta Bromo Toluene and Bromo Durene based on density functional calculations

    NASA Astrophysics Data System (ADS)

    Krishna Kumar, V.; Suganya, S.; Mathammal, R.

    This work deals with the vibrational spectra of 2,3,4,5,6-Penta Bromo Toluene (PBT) and Bromo Durene (BD) by quantum chemical calculations. The solid phase FTIR and FT-Raman spectra of the title compounds were recorded in the regions 4000-400 cm-1 and 4000-50 cm-1, respectively. The spectra were interpreted with the aid of normal coordinate analysis based on density functional theory (DFT) using B3LYP/6-31G? level and basis set combinations and was scaled using various scale factors yielding a good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. The HOMO and LUMO energies were calculated within the molecule. 13C and 1H NMR chemical shifts results were also calculated and compared with the experimental values. Thermodynamical properties like entropy heat capacity, zero point energy have been calculated for the title molecules.

  2. Vibrational frequency analysis, FT-IR, FT-Raman, ab initio, HF and DFT studies, NBO, HOMO-LUMO and electronic structure calculations on pycolinaldehyde oxime

    NASA Astrophysics Data System (ADS)

    Suvitha, A.; Periandy, S.; Boomadevi, S.; Govindarajan, M.

    2014-01-01

    In this work, the vibrational spectral analysis is carried out by using Raman and infrared spectroscopy in the range 100-4000 cm-1and 50-4000 cm-1, respectively, for pycolinaldehyde oxime (PAO) (C6H6N2O) molecule. The vibrational frequencies have been calculated and scaled values are compared with experimental FT-IR and FT-Raman spectra. The structure optimizations and normal coordinate force field calculations are based on HF and B3LYP methods with 6-311++G(d,p) basis set. The results of the calculation shows excellent agreement between experimental and calculated frequencies in B3LYP/6-311++G(d,p) basis set. The optimized geometric parameters are compared with experimental values of PAO. The non linear optical properties, NBO analysis, thermodynamics properties and mulliken charges of the title molecule are also calculated and interpreted. A study on the electronic properties, such as HOMO and LUMO energies, are performed by time-dependent DFT (TD-DFT) approach. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) are performed. The effects due to the substitutions of CHdbnd NOH ring are investigated. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results.

  3. Vibrational frequency analysis, FT-IR, FT-Raman, ab initio, HF and DFT studies, NBO, HOMO-LUMO and electronic structure calculations on pycolinaldehyde oxime.

    PubMed

    Suvitha, A; Periandy, S; Boomadevi, S; Govindarajan, M

    2014-01-01

    In this work, the vibrational spectral analysis is carried out by using Raman and infrared spectroscopy in the range 100-4000 cm(-1)and 50-4000 cm(-1), respectively, for pycolinaldehyde oxime (PAO) (C6H6N2O) molecule. The vibrational frequencies have been calculated and scaled values are compared with experimental FT-IR and FT-Raman spectra. The structure optimizations and normal coordinate force field calculations are based on HF and B3LYP methods with 6-311++G(d,p) basis set. The results of the calculation shows excellent agreement between experimental and calculated frequencies in B3LYP/6-311++G(d,p) basis set. The optimized geometric parameters are compared with experimental values of PAO. The non linear optical properties, NBO analysis, thermodynamics properties and mulliken charges of the title molecule are also calculated and interpreted. A study on the electronic properties, such as HOMO and LUMO energies, are performed by time-dependent DFT (TD-DFT) approach. Besides, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) are performed. The effects due to the substitutions of CH=NOH ring are investigated. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. PMID:23994677

  4. Molecular structure, vibrational spectroscopic, NBO and HOMO–LUMO studies of 2-amino 6-bromo 3-formylchromone

    Microsoft Academic Search

    Archana Gupta; Saba Bee; Neetu Choudhary; Soni Mishra; Poonam Tandon

    2012-01-01

    A systematic quantum mechanical study of the possible conformations and vibrational spectra of 2-amino 6-bromo 3-formylchromone has been reported. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by Hartree–Fock and density functional theory employing Becke's three-parameter (local, non-local and HF) hybrid exchange functionals with Lee–Yang–Parr co-relational (B3LYP) functionals using 6-311++G(d,p) basis set with

  5. MULTIMODE quantum calculations of vibrational energies and IR spectrum of the NO{sup +}(H{sub 2}O) cluster using accurate potential energy and dipole moment surfaces

    SciTech Connect

    Homayoon, Zahra, E-mail: zhomayo@emory.edu [Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322 (United States)

    2014-09-28

    A new, full (nine)-dimensional potential energy surface and dipole moment surface to describe the NO{sup +}(H{sub 2}O) cluster is reported. The PES is based on fitting of roughly 32?000 CCSD(T)-F12/aug-cc-pVTZ electronic energies. The surface is a linear least-squares fit using a permutationally invariant basis with Morse-type variables. The PES is used in a Diffusion Monte Carlo study of the zero-point energy and wavefunction of the NO{sup +}(H{sub 2}O) and NO{sup +}(D{sub 2}O) complexes. Using the calculated ZPE the dissociation energies of the clusters are reported. Vibrational configuration interaction calculations of NO{sup +}(H{sub 2}O) and NO{sup +}(D{sub 2}O) using the MULTIMODE program are performed. The fundamental, a number of overtone, and combination states of the clusters are reported. The IR spectrum of the NO{sup +}(H{sub 2}O) cluster is calculated using 4, 5, 7, and 8 modes VSCF/CI calculations. The anharmonic, coupled vibrational calculations, and IR spectrum show very good agreement with experiment. Mode coupling of the water “antisymmetric” stretching mode with the low-frequency intermolecular modes results in intensity borrowing.

  6. MULTIMODE quantum calculations of vibrational energies and IR spectrum of the NO?(H?O) cluster using accurate potential energy and dipole moment surfaces.

    PubMed

    Homayoon, Zahra

    2014-09-28

    A new, full (nine)-dimensional potential energy surface and dipole moment surface to describe the NO(+)(H2O) cluster is reported. The PES is based on fitting of roughly 32,000 CCSD(T)-F12/aug-cc-pVTZ electronic energies. The surface is a linear least-squares fit using a permutationally invariant basis with Morse-type variables. The PES is used in a Diffusion Monte Carlo study of the zero-point energy and wavefunction of the NO(+)(H2O) and NO(+)(D2O) complexes. Using the calculated ZPE the dissociation energies of the clusters are reported. Vibrational configuration interaction calculations of NO(+)(H2O) and NO(+)(D2O) using the MULTIMODE program are performed. The fundamental, a number of overtone, and combination states of the clusters are reported. The IR spectrum of the NO(+)(H2O) cluster is calculated using 4, 5, 7, and 8 modes VSCF/CI calculations. The anharmonic, coupled vibrational calculations, and IR spectrum show very good agreement with experiment. Mode coupling of the water "antisymmetric" stretching mode with the low-frequency intermolecular modes results in intensity borrowing. PMID:25273441

  7. Nonlinear Analysis and Experiments on Torsional Vibration of a Rotor with a Centrifugal Pendulum Vibration Absorber

    NASA Astrophysics Data System (ADS)

    Ishida, Yukio; Inoue, Tsuyoshi; Kagawa, Taishi; Ueda, Motohiko

    In the rotating machinery, such as automobile engines, the driving torque changes periodically and torsional vibrations occur. In this study, the dynamic characteristics of centrifugal pendulum vibration absorbers which are used to suppress torsional vibrations are investigated both theoretically and experimentally. In the theoretical analysis, the nonlinear characteristics are taken into consideration under the assumption that the pendulums vibrate with large amplitude. It is clarified that, although the centrifugal pendulum has remarkable effects on suppressing harmonic vibration, it induces large amplitude harmonic vibrations, the second and third order superharmonic resonances, and unstable vibrations of harmonic type under some condition,. Moreover, this paper proposes various methods to suppress these secondarily induced vibrations, and show that it is possible to suppress torsional vibrations to the substantially zero amplitude-level in the whole rotational speed range.

  8. Structural and vibrational study of maprotiline

    NASA Astrophysics Data System (ADS)

    Yavuz, A. E.; Haman Bayar?, S.; Kazanc?, N.

    2009-04-01

    Maprotiline ( N-methyl-9,10-ethanoanthracene-9(10H)-propanamine) is a tetra cyclic antidepressant. It is a highly selective inhibitor of norepinephrine reuptake. The solid and solution in CCl 4 and methanol infrared spectra of maprotiline were recorded. The fully optimized equilibrium structure of maprotiline was obtained from DFT calculations by using the B3LYP functional in combination with 6-31G and 6-311G(d,p) basis sets. The results of harmonic and anharmonic frequency calculations on maprotiline were presented. The vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical (SQM) force field. Vibrational assignment of all the fundamentals was made using the total energy distribution (TED). The possible interaction between maprotiline and neurotransmitter serotonin (5-HT) were investigated.

  9. Updated references for the structural, electronic, and vibrational properties of TiO2(B) bulk using first-principles density functional theory calculations.

    PubMed

    Ben Yahia, Mouna; Lemoigno, Frédéric; Beuvier, Thomas; Filhol, Jean-Sébastien; Richard-Plouet, Mireille; Brohan, Luc; Doublet, Marie-Liesse

    2009-05-28

    To get updated references on the structural, electronic, and vibration properties of the metastable TiO(2)(B) compound, infrared and Raman spectra of TiO(2)(B) are computed within the density functional theory framework and all active modes are assigned. Phonons and their possible coupling with the macroscopic electric fields resulting from the long-range interactions of instantaneous local dipoles (due to nuclear vibrations) in polar solids are taken into account through supercell calculations and longitudinal optical-transversal optical splitting corrections. Full structural relaxations using conventional density functional theory and hybrid functionals with localized Gaussian-type orbitals or plane-wave basis sets reveal a similar deviation of the local Ti environment compared to the TiO(2)(B) structural refinements reported so far. Such deviations are shown to be significant from those computed for anatase using the same method, thus yielding distinguishable spectroscopic responses for the two polymorphs. PMID:19485451

  10. Ab initio calculation of a global potential, vibrational energies, and wave functions for HCN/HNC, and a simulation of the (A-tilde)-(X-tilde) emission spectrum

    NASA Technical Reports Server (NTRS)

    Bowman, Joel M.; Gazdy, Bela; Bentley, Joseph A.; Lee, Timothy J.; Dateo, Christopher E.

    1993-01-01

    A potential energy surface for the HCN/HNC system which is a fit to extensive, high-quality ab initio, coupled-cluster calculations is presented. All HCN and HNC states with energies below the energy of the first delocalized state are reported and characterized. Vibrational transition energies are compared with all available experimental data on HCN and HNC, including high CH-overtone states up to 23,063/cm. A simulation of the (A-tilde)-(X-tilde) stimulated emission pumping (SEP) spectrum is also reported, and the results are compared to experiment. Franck-Condon factors are reported for odd bending states of HCN, with one quantum of vibrational angular momentum, in order to compare with the recent assignment by Jonas et al. (1992), on the basis of axis-switching arguments of a number of previously unassigned states in the SEP spectrum.

  11. Static and dynamic coupled perturbed Hartree-Fock vibrational (hyper)polarizabilities of polyacetylene calculated by the finite field nuclear relaxation method

    NASA Astrophysics Data System (ADS)

    Lacivita, Valentina; Rérat, Michel; Kirtman, Bernard; Orlando, Roberto; Ferrabone, Matteo; Dovesi, Roberto

    2012-07-01

    The vibrational contribution to static and dynamic (hyper)polarizability tensors of polyacetylene are theoretically investigated. Calculations were carried out by the finite field nuclear relaxation (FF-NR) method for periodic systems, newly implemented in the CRYSTAL code, using the coupled perturbed Hartree-Fock scheme for the required electronic properties. The effect of the basis set is also explored, being particularly important for the non-periodic direction perpendicular to the polymer plane. Components requiring a finite (static) field in the longitudinal direction for evaluation by the FF-NR method were not evaluated. The extension to that case is currently being pursued. Whereas the effect on polarizabilities is relatively small, in most cases the vibrational hyperpolarizability tensor component is comparable to, or larger than the corresponding static electronic contribution.

  12. Calculation of vibrational energy levels of triatomic molecules with the C 2v and C s symmetries by summing divergent series of the Rayleigh-Schrödinger perturbation theory

    NASA Astrophysics Data System (ADS)

    Bykov, A. D.; Kalinin, K. V.

    2012-03-01

    The Rayleigh-Schrödinger perturbation theory is applied to calculation of vibrational energy levels of triatomic molecules with the C 2v and C s symmetries: SO2, H2S, F2O, HOF, HOCl, and DOCl. Particular attention is given to the states coupled by anharmonic resonances; for such states, the perturbation theory series diverge. To sum these series, the known methods of Padé, Padé-Borel, and Padé-Hermite and the method of power moments are used. For low-lying levels, all the summation methods give satisfactory results, while the method of quadratic Padé-Hermite approximants appears to be more efficient for high-excited states. Using these approximants, the structure of singularities of the vibrational energy, as a function in the complex plane, is studied.

  13. PHYSICAL REVIEW B 85, 224303 (2012) Mixed-space approach for calculation of vibration-induced dipole-dipole interactions

    E-print Network

    Chen, Long-Qing

    2012-01-01

    . INTRODUCTION The phonon approach1,2 is currently the most efficient method for predicting thermodynamic properties of a solid at finite temperatures. It has been implemented under the frame- work of first. Lyddane et al.8 first accurately formulated the polar vibrations of cubic alkali halides in the long wave

  14. Calculation of Rotation-Vibration Energy Levels of the Water Molecule with Near-Experimental Accuracy Based on an ab Initio Potential Energy Surface

    NASA Astrophysics Data System (ADS)

    Polyansky, Oleg L.; Ovsyannikov, Roman I.; Kyuberis, Aleksandra A.; Lodi, Lorenzo; Tennyson, Jonathan; Zobov, Nikolai F.

    2013-10-01

    A recently computed, high-accuracy ab initio Born-Oppenheimer (BO) potential energy surface (PES) for the water molecule is combined with relativistic, adiabatic, quantum electrodynamics, and, crucially, nonadiabatic corrections. Calculations of ro-vibrational levels are presented for several water isotopologues and shown to have unprecedented accuracy. A purely ab initio calculation reproduces some 200 known band origins associated with seven isotopologues of water with a standard deviation (?) of about 0.35 cm-1. Introducing three semiempirical scaling parameters, two affecting the BO PES and one controlling nonadiabatic effects, reduces ? below 0.1 cm-1. Introducing one further rotational nonadiabatic parameter gives ? better than 0.1 cm-1 for all observed ro-vibrational energy levels up to J = 25. We conjecture that the energy levels of closed-shell molecules with roughly the same number of electrons as water, such as NH3, CH4, and H3O+, could be calculated to this accuracy using an analogous procedure. This means that near-ab initio calculations are capable of predicting transition frequencies with an accuracy only about a factor of 5 worse than high resolution experiments.

  15. Ab initio and DFT studies of the vibrational spectra of benzofuran and some of its derivatives

    NASA Astrophysics Data System (ADS)

    Singh, V. B.

    2006-12-01

    The vibrational spectra of benzofuran and some of its derivatives have been systematically investigated by ab initio and density functional B3LYP methods. The harmonic vibrational wavenumbers and intensity of vibrational bands were calculated at ab initio and DFT levels invoking different basis sets up to 6-311++g**. Vibrational assignments have been made and it has been found that the calculated DFT frequencies agree well in most cases with the observed frequencies for each molecule. Conformational studies have also been carried out and it is evident from ab initio calculations that 2(3H) benzofuranone is more stable than 3(2H) benzofuranone in support to our earlier semiempirical results.

  16. Optimal geometries and harmonic vibrational frequencies of the global minima of water clusters (H2O)n, n = 2-6, and several hexamer local minima at the CCSD(T) level of theory.

    PubMed

    Miliordos, Evangelos; Aprà, Edoardo; Xantheas, Sotiris S

    2013-09-21

    We report the first optimum geometries and harmonic vibrational frequencies for the ring pentamer and several water hexamer (prism, cage, cyclic and two book) at the coupled-cluster including single, double, and full perturbative triple excitations (CCSD(T))/aug-cc-pVDZ level of theory. All five examined hexamer isomer minima previously reported by Møller-Plesset perturbation theory (MP2) are also minima on the CCSD(T) potential energy surface (PES). In addition, all CCSD(T) minimum energy structures for the n = 2-6 cluster isomers are quite close to the ones previously obtained by MP2 on the respective PESs, as confirmed by a modified Procrustes analysis that quantifies the difference between any two cluster geometries. The CCSD(T) results confirm the cooperative effect of the homodromic ring networks (systematic contraction of the nearest-neighbor (nn) intermolecular separations with cluster size) previously reported by MP2, albeit with O-O distances shorter by ~0.02 Å, indicating that MP2 overcorrects this effect. The harmonic frequencies at the minimum geometries were obtained by the double differentiation of the CCSD(T) energy using an efficient scheme based on internal coordinates that reduces the number of required single point energy evaluations by ~15% when compared to the corresponding double differentiation using Cartesian coordinates. Negligible differences between MP2 and CCSD(T) frequencies are found for the librational modes, while uniform increases of ~15 and ~25 cm(-1) are observed for the bending and "free" OH harmonic frequencies. The largest differences between CCSD(T) and MP2 are observed for the harmonic hydrogen bonded frequencies, for which the former produces larger absolute values than the latter. Their CCSD(T) redshifts from the monomer values (??) are smaller than the MP2 ones, due to the fact that CCSD(T) produces shorter elongations (?R) of the respective hydrogen bonded OH lengths from the monomer value with respect to MP2. Both the MP2 and CCSD(T) results for the hydrogen bonded frequencies were found to closely follow the relation -?? = s · ?R, with a rate of s = 20.2 cm(-1)/0.001 Å for hydrogen bonded frequencies with IR intensities >400 km/mol. The CCSD(T) harmonic frequencies, when corrected using the MP2 anharmonicities obtained from second order vibrational perturbation theory, produce anharmonic CCSD(T) estimates that are within <60 cm(-1) from the measured infrared (IR) active bands of the n = 2-6 clusters. Furthermore, the CCSD(T) harmonic redshifts (with respect to the monomer) trace the measured ones quite accurately. The energetic order between the various hexamer isomers on the PES (prism has the lowest energy) previously reported at MP2 was found to be preserved at the CCSD(T) level, whereas the inclusion of anharmonic corrections further stabilizes the cage among the hexamer isomers. PMID:24070285

  17. Optimal geometries and harmonic vibrational frequencies of the global minima of water clusters (H2O)n, n = 2-6, and several hexamer local minima at the CCSD(T) level of theory

    NASA Astrophysics Data System (ADS)

    Miliordos, Evangelos; Aprà, Edoardo; Xantheas, Sotiris S.

    2013-09-01

    We report the first optimum geometries and harmonic vibrational frequencies for the ring pentamer and several water hexamer (prism, cage, cyclic and two book) at the coupled-cluster including single, double, and full perturbative triple excitations (CCSD(T))/aug-cc-pVDZ level of theory. All five examined hexamer isomer minima previously reported by Møller-Plesset perturbation theory (MP2) are also minima on the CCSD(T) potential energy surface (PES). In addition, all CCSD(T) minimum energy structures for the n = 2-6 cluster isomers are quite close to the ones previously obtained by MP2 on the respective PESs, as confirmed by a modified Procrustes analysis that quantifies the difference between any two cluster geometries. The CCSD(T) results confirm the cooperative effect of the homodromic ring networks (systematic contraction of the nearest-neighbor (nn) intermolecular separations with cluster size) previously reported by MP2, albeit with O-O distances shorter by ˜0.02 Å, indicating that MP2 overcorrects this effect. The harmonic frequencies at the minimum geometries were obtained by the double differentiation of the CCSD(T) energy using an efficient scheme based on internal coordinates that reduces the number of required single point energy evaluations by ˜15% when compared to the corresponding double differentiation using Cartesian coordinates. Negligible differences between MP2 and CCSD(T) frequencies are found for the librational modes, while uniform increases of ˜15 and ˜25 cm-1 are observed for the bending and "free" OH harmonic frequencies. The largest differences between CCSD(T) and MP2 are observed for the harmonic hydrogen bonded frequencies, for which the former produces larger absolute values than the latter. Their CCSD(T) redshifts from the monomer values (??) are smaller than the MP2 ones, due to the fact that CCSD(T) produces shorter elongations (?R) of the respective hydrogen bonded OH lengths from the monomer value with respect to MP2. Both the MP2 and CCSD(T) results for the hydrogen bonded frequencies were found to closely follow the relation -?? = s . ?R, with a rate of s = 20.2 cm-1/0.001 Å for hydrogen bonded frequencies with IR intensities >400 km/mol. The CCSD(T) harmonic frequencies, when corrected using the MP2 anharmonicities obtained from second order vibrational perturbation theory, produce anharmonic CCSD(T) estimates that are within <60 cm-1 from the measured infrared (IR) active bands of the n = 2-6 clusters. Furthermore, the CCSD(T) harmonic redshifts (with respect to the monomer) trace the measured ones quite accurately. The energetic order between the various hexamer isomers on the PES (prism has the lowest energy) previously reported at MP2 was found to be preserved at the CCSD(T) level, whereas the inclusion of anharmonic corrections further stabilizes the cage among the hexamer isomers.

  18. Vibrational spectrum of brucite, Mg(OH) 2: a periodic ab initio quantum mechanical calculation including OH anharmonicity

    Microsoft Academic Search

    Fabien Pascale; Sergio Tosoni; Claudio Zicovich-Wilson; Piero Ugliengo; Roberto Orlando; Roberto Dovesi

    2004-01-01

    The harmonic frequency spectrum of bulk Mg(OH)2, brucite, has been computed with the CRYSTAL periodic code, using four different hamiltonians, namely Hartree–Fock (HF), local density (LDA), gradient corrected PW91 and hybrid B3LYP. The anharmonicity of the OH stretching frequency has also been evaluated, as well as the transverse\\/longitudinal optical (TO\\/LO) splitting. Comparison with the frequencies of the single layer shows

  19. Gas-phase vibrational spectroscopy and ab initio study of organophosphorus compounds: discrimination between species and conformers.

    PubMed

    Cuisset, A; Mouret, G; Pirali, O; Roy, P; Cazier, F; Nouali, H; Demaison, J

    2008-10-01

    Gas phase vibrational spectra of dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), and triethyl phosphate (TEP) have been measured using FTIR spectroscopy. For DMMP, TMP, and TEP, most of the infrared active vibrational modes have been observed in the 50-5000 cm (-1) spectral range, allowing an unambiguous discrimination between the three molecules. The vibrational analysis of the spectra was performed by comparing with MP2 and B3LYP harmonic and anharmonic force field ab initio calculations. The extension to anharmonic calculations provides the best agreement for the mid-infrared and the near-infrared spectra, but they do not improve the harmonic frequency predictions in the far-infrared domain. This part of the vibrational spectra associated with collective and nonlocalized vibrational modes presents the largest frequency differences between the two lowest energy conformers of DMMP and TMP. These two conformers were taken into account in the vibrational assignment of the spectra. Their experimental evidence was obtained by deconvoluting vibrational bands in the mid-infrared and in the far-infrared regions, respectively. For TEP, the conformational landscape appears very complicated at ambient temperature, and a further analysis at low temperature is required to explain the vibrational features of each conformer. PMID:18781711

  20. Intramolecular Dynamics Probed using High Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Hooper, Robynne; Zhou, Xibin; Li, Wen; Wagner, Nick; Kapteyn, Henry; Murnane, Margaret

    2007-06-01

    We observed intramolecular dynamics as a modulation in high harmonic emission. We excite coherent vibrations in CF3Cl using impulsive Raman scattering with a short laser pulse. A second laser pulse generates high harmonics. The harmonic yield is observed to oscillate at frequencies corresponding to three vibrational modes of CF3Cl. In a second experiment, we used UV light to excite and dissociate CF3I, and follow the dynamic evolution by monitoring the harmonic yield. We observe a large modulation of the harmonic yield, likely due to resonance excitation and subsequent dissociation of the molecule. We speculate that the less-than full baseline recovery after the UV pulse is due to ionization, and that the harmonic yield is sensitive to the bond length during dissociation. By these two experiments, we confirm that high harmonic generation is a sensitive probe of intramolecular dynamics and may yield more information simultaneously than conventional ultrafast spectroscopic techniques.

  1. Synthesis, structural and vibrational investigation on 2-phenyl-N-(pyrazin-2-yl)acetamide combining XRD diffraction, FT-IR and NMR spectroscopies with DFT calculations

    NASA Astrophysics Data System (ADS)

    Lukose, Jilu; Yohannan Panicker, C.; Nayak, Prakash S.; Narayana, B.; Sarojini, B. K.; Van Alsenoy, C.; Al-Saadi, Abdulaziz A.

    2015-01-01

    The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2-phenyl-N-(pyrazin-2-yl)acetamide have been investigated experimentally and theoretically using Gaussian09 software package. The title compound was optimized by using the HF/6-31G(6D,7F) and B3LYP/6-31G(6D,7F) calculations. The geometrical parameters are in agreement with the XRD data. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. Gauge-including atomic orbital 1H-NMR chemical shifts calculations were carried out and compared with experimental data. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. Molecular electrostatic potential was performed by the DFT method. First hyperpolarizability is calculated in order to find its role in non linear optics. From the XRD data, in the crystal, molecules are held together by strong Csbnd H⋯O and Nsbnd H⋯O intermolecular interactions.

  2. Synthesis, structural and vibrational investigation on 2-phenyl-N-(pyrazin-2-yl)acetamide combining XRD diffraction, FT-IR and NMR spectroscopies with DFT calculations.

    PubMed

    Lukose, Jilu; Yohannan Panicker, C; Nayak, Prakash S; Narayana, B; Sarojini, B K; Van Alsenoy, C; Al-Saadi, Abdulaziz A

    2015-01-25

    The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2-phenyl-N-(pyrazin-2-yl)acetamide have been investigated experimentally and theoretically using Gaussian09 software package. The title compound was optimized by using the HF/6-31G(6D,7F) and B3LYP/6-31G(6D,7F) calculations. The geometrical parameters are in agreement with the XRD data. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. Gauge-including atomic orbital (1)H-NMR chemical shifts calculations were carried out and compared with experimental data. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. Molecular electrostatic potential was performed by the DFT method. First hyperpolarizability is calculated in order to find its role in non linear optics. From the XRD data, in the crystal, molecules are held together by strong C-H?O and N-H?O intermolecular interactions. PMID:25124846

  3. A DFT study of the geometries and vibrational spectra of indene and some of its heterocyclic analogues, benzofuran, benzoxazole, bensothiophene, benzothiazole, indole and indazole

    NASA Astrophysics Data System (ADS)

    El-Azhary, A. A.

    1999-10-01

    Ab-initio optimized geometries and harmonic force fields were calculated for indene, 1; benzofuran, 2; benzoxazole, 3; benzothiophene, 4; benzothiazole, 5; indole, 6; and indazole, 7, at the HF and B3LYP levels of theory using the 6-31G** basis set. A planar Cs symmetry was assumed in all calculations. The force fields of 1- 6 were scaled with respect to the experimental frequencies available in literature. The calculated frequencies confirmed the experimental assignment of these molecules, 1- 6. The calculated scale factors were used to calculate vibrational frequencies of 7 and showed possible misassignments in the experimental vibrational frequencies of 7.

  4. Hybrid BEM\\/FEM Calculation of Thermal Rise in the Human Eye Exposed to Time Harmonic EM Waves

    Microsoft Academic Search

    Hrvoje Dodig

    2005-01-01

    Human eye being unprotected by the layer of skin and bones is one of the most sensitive organs to EM radiation. The absorption of EM radiation is quantified in terms of SAR and to calculate the SAR the knowledge of complete electric field distribution inside the eye is necessary. In this paper the problem of distribution of near EM field

  5. Theoretical and experimental study of vibrational spectra of two polymorphic 4-hydroxy-1-methylpiperidine betaine hydrochlorides

    NASA Astrophysics Data System (ADS)

    Szafran, M.; Koput, J.; Dega-Szafran, Z.

    2008-09-01

    The molecular geometries, harmonic frequencies and intensities of the vibrational bands of ? and ? polymorphs of 4-hydroxy-1-methylpiperidine betaine hydrochloride (?-HO-MPBH·Cl, ?-HO-MPBH·Cl) and their deuterated derivatives have been calculated with the B3LYP/6-31G(d,p) level of theory. The calculated frequencies are compared with the solid FTIR and Raman spectra. Unequivocal assignments of the experimental infrared bands are performed on the basis of the potential energy distribution (PED).

  6. Theoretical and experimental study of vibrational spectra of two polymorphic 4-hydroxy-1-methylpiperidine betaine hydrochlorides

    Microsoft Academic Search

    M. Szafran; J. Koput; Z. Dega-Szafran

    2008-01-01

    The molecular geometries, harmonic frequencies and intensities of the vibrational bands of ? and ? polymorphs of 4-hydroxy-1-methylpiperidine betaine hydrochloride (?-HO-MPBH·Cl, ?-HO-MPBH·Cl) and their deuterated derivatives have been calculated with the B3LYP\\/6-31G(d,p) level of theory. The calculated frequencies are compared with the solid FTIR and Raman spectra. Unequivocal assignments of the experimental infrared bands are performed on the basis of

  7. Emission spectroscopy, harmonic vibrational frequencies, and improved ground state structures of jet-cooled monochloro- and monobromosilylene (HSiCl and HSiBr)

    Microsoft Academic Search

    David A. Hostutler; Nicholas Ndiege; Dennis J. Clouthier; Steven W. Pauls

    2001-01-01

    The ground state harmonic frequencies of gas phase H\\/DSi35Cl and H\\/DSi79Br have been determined by exciting single vibronic bands of the A~ 1A''-X~ 1A' electronic transition and recording the dispersed fluorescence. The jet-cooled radicals were produced in a pulsed discharge jet using H\\/DSiX3 (X=Cl or Br) precursors. The emission data were fitted to an anharmonic model and a normal coordinate

  8. Emission spectroscopy, harmonic vibrational frequencies, and improved ground state structures of jet-cooled monochloro- and monobromosilylene (HSiCl and HSiBr)

    Microsoft Academic Search

    David A. Hostutler; Nicholas Ndiege; Dennis J. Clouthier; Steven W. Pauls

    2001-01-01

    The ground state harmonic frequencies of gas phase H\\/DSi35Cl and H\\/DSi79Br have been determined by exciting single vibronic bands of the à 1A?–X˜ 1A? electronic transition and recording the dispersed fluorescence. The jet-cooled radicals were produced in a pulsed discharge jet using H\\/DSiX3(X=Cl or Br) precursors. The emission data were fitted to an anharmonic model and a normal coordinate analysis

  9. A method for sensorless on-line vibration monitoring of induction machines

    Microsoft Academic Search

    Caryn M. Riley; Brian K. Lin; Thomas G. Habetler; Randy R. Schoen

    1997-01-01

    This paper proposes a method for sensorless on-line vibration monitoring of induction machines based on the relationship between the current harmonics in the machine and their related vibration harmonics. Initially, the vibration monitoring system records two baseline measurements of current and vibration with the machine operating under normal conditions. The baseline data is then evaluated to determine the critical frequencies

  10. A method for sensorless on-line vibration monitoring of induction machines

    Microsoft Academic Search

    Caryn M. Riley; Brian K. Lin; Thomas G. Habetler; Randy R. Schoen

    1998-01-01

    This paper proposes a method for the sensorless online vibration monitoring of induction machines based on the relationship between the current harmonics in the machine and their related vibration harmonics. Initially, the vibration monitoring system records two baseline measurements of current and vibration with the machine operating under normal conditions. The baseline data is then evaluated to determine the critical

  11. Analysis on Non-Resonance Standing Waves and Vibration Tracks of Strings

    ERIC Educational Resources Information Center

    Fang, Tian-Shen

    2007-01-01

    This paper presents an experimental technique to observe the vibration tracks of string standing waves. From the vibration tracks, we can analyse the vibration directions of harmonic waves. For the harmonic wave vibrations of strings, when the driving frequency f[subscript s] = Nf[subscript n] (N = 1, 2, 3, 4,...), both resonance and non-resonance…

  12. X-ray crystal structure, vibrational spectra and DFT calculations of 3-chloro-7-azaindole: A case of dual N-H⋯N hydrogen bonds in dimers

    NASA Astrophysics Data System (ADS)

    Morzyk-Ociepa, Barbara; Dysz, Karolina; Turowska-Tyrk, Ilona; Michalska, Danuta

    2015-02-01

    3-Chloro-7-azaindole (3Cl7AI) is the carrier ligand in a new anticancer platinum(II) agent cis-[PtCl2(3Cl7AI)2]. In this work 3Cl7AI has been studied by a single crystal X-ray diffraction, infrared and Raman spectroscopy and density functional calculations. The compound crystallizes in the monoclinic system, space group P21/n, with a = 12.3438(3), b = 3.85964(11), c = 14.4698(4) Å, ? = 100.739(2)°, V = 677.31(3) Å3 and Z = 4. In the crystal, a pair of 3Cl7AI molecules forms a centrosymmetric dimer linked by the moderately strong dual N-H⋯N hydrogen bonds. The nitrogen atom in the pyrrole ring acts as the proton donor, while the nitrogen atom in the pyridine ring is the proton acceptor. The FT-IR and FT-Raman spectra (3500-60 cm-1) have been recorded. The theoretical studies on the molecular structures and vibrational spectra of the monomeric and dimeric forms of 3Cl7AI and its N-deuterated derivative were performed using the B3LYP method with 6-311++G(d,p) basis set. The theoretically predicted Raman spectrum for the dimer shows very good agreement with experiment. Detailed vibrational assignments for the two isotopomers have been made on the basis of the calculated potential energy distributions (PEDs). The dual N-H⋯N hydrogen bonds in 3Cl7AI dimer are characterized by a very broad and complicated structure of the absorption band between 3300 and 2500 cm-1, which is caused by multiple Fermi resonances between the N-H stretching vibration and various combinations bands.

  13. X-ray crystal structure, vibrational spectra and DFT calculations of 3-chloro-7-azaindole: a case of dual N-H?N hydrogen bonds in dimers.

    PubMed

    Morzyk-Ociepa, Barbara; Dysz, Karolina; Turowska-Tyrk, Ilona; Michalska, Danuta

    2015-02-01

    3-Chloro-7-azaindole (3Cl7AI) is the carrier ligand in a new anticancer platinum(II) agent cis-[PtCl2(3Cl7AI)2]. In this work 3Cl7AI has been studied by a single crystal X-ray diffraction, infrared and Raman spectroscopy and density functional calculations. The compound crystallizes in the monoclinic system, space group P21/n, with a=12.3438(3), b=3.85964(11), c=14.4698(4)Å, ?=100.739(2)°, V=677.31(3)Å(3) and Z=4. In the crystal, a pair of 3Cl7AI molecules forms a centrosymmetric dimer linked by the moderately strong dual N-H?N hydrogen bonds. The nitrogen atom in the pyrrole ring acts as the proton donor, while the nitrogen atom in the pyridine ring is the proton acceptor. The FT-IR and FT-Raman spectra (3500-60 cm(-1)) have been recorded. The theoretical studies on the molecular structures and vibrational spectra of the monomeric and dimeric forms of 3Cl7AI and its N-deuterated derivative were performed using the B3LYP method with 6-311++G(d,p) basis set. The theoretically predicted Raman spectrum for the dimer shows very good agreement with experiment. Detailed vibrational assignments for the two isotopomers have been made on the basis of the calculated potential energy distributions (PEDs). The dual N-H?N hydrogen bonds in 3Cl7AI dimer are characterized by a very broad and complicated structure of the absorption band between 3300 and 2500 cm(-1), which is caused by multiple Fermi resonances between the N-H stretching vibration and various combinations bands. PMID:25315872

  14. Near spectroscopically accurate ab initio potential energy surface for NH4(+) and variational calculations of low-lying vibrational levels.

    PubMed

    Han, Huixian; Song, Hongwei; Li, Jun; Guo, Hua

    2015-04-01

    A nine-dimensional potential energy surface (PES) for the ammonium cation has been constructed by fitting ?30?000 AE-CCSD(T)-F12a/cc-pCVTZ-F12 points up to 32?262 cm(-1) (4.0 eV) from the minimum. The fitting using the permutation invariant polynomial-neural network method has high fidelity, with a root-mean-square error of merely 2.34 cm(-1). The low-lying vibrational energy levels of NH4(+) have been determined quantum mechanically using both Jacobi and normal coordinates, and the fundamental frequencies are in excellent agreement with available experimental data. PMID:25781209

  15. Strong second harmonic generation in SiC, ZnO, GaN two-dimensional hexagonal crystals from first-principles many-body calculations.

    PubMed

    Attaccalite, C; Nguer, A; Cannuccia, E; Grüning, M

    2015-04-14

    The second harmonic generation (SHG) intensity spectrum of SiC, ZnO, GaN two-dimensional hexagonal crystals is calculated by using a real-time first-principles approach based on Green's function theory [Attaccalite et al., Phys. Rev. B: Condens. Matter Mater. Phys. 2013 88, 235113]. This approach allows one to go beyond the independent particle description used in standard first-principles nonlinear optics calculations by including quasiparticle corrections (by means of the GW approximation), crystal local field effects and excitonic effects. Our results show that the SHG spectra obtained using the latter approach differ significantly from their independent particle counterparts. In particular they show strong excitonic resonances at which the SHG intensity is about two times stronger than within the independent particle approximation. All the systems studied (whose stabilities have been predicted theoretically) are transparent and at the same time exhibit a remarkable SHG intensity in the range of frequencies at which Ti:sapphire and Nd:YAG lasers operate; thus they can be of interest for nanoscale nonlinear frequency conversion devices. Specifically the SHG intensity at 800 nm (1.55 eV) ranges from about 40-80 pm V(-1) in ZnO and GaN to 0.6 nm V(-1) in SiC. The latter value in particular is 1 order of magnitude larger than values in standard nonlinear crystals. PMID:25766901

  16. Extended aeroelastic analysis for helicopter rotors with prescribed hub motion and blade appended penduluum vibration absorbers

    NASA Technical Reports Server (NTRS)

    Bielawa, R. L.

    1984-01-01

    The mathematical development for the expanded capabilities of the G400 rotor aeroelastic analysis was examined. The G400PA expanded analysis simulates the dynamics of all conventional rotors, blade pendulum vibration absorbers, and the higher harmonic excitations resulting from prescribed vibratory hub motions and higher harmonic blade pitch control. The methodology for modeling the unsteady stalled airloads of two dimensional airfoils is discussed. Formulations for calculating the rotor impedance matrix appropriate to the higher harmonic blade excitations are outlined. This impedance matrix, and the associated vibratory hub loads, are the rotor dynamic characteristic elements for use in the simplified coupled rotor/fuselage vibration analysis (SIMVIB). Updates to the development of the original G400 theory, program documentation, user instructions and information are presented.

  17. Electronic [UV-Visible] and vibrational [FT-IR, FT-Raman] investigation and NMR-mass spectroscopic analysis of terephthalic acid using quantum Gaussian calculations

    NASA Astrophysics Data System (ADS)

    Karthikeyan, N.; Joseph Prince, J.; Ramalingam, S.; Periandy, S.

    2015-03-01

    In this research work, the vibrational IR, polarization Raman, NMR and mass spectra of terephthalic acid (TA) were recorded. The observed fundamental peaks (IR, Raman) were assigned according to their distinctiveness region. The hybrid computational calculations were carried out for calculating geometrical and vibrational parameters by DFT (B3LYP and B3PW91) methods with 6-31++G(d,p) and 6-311++G(d,p) basis sets and the corresponding results were tabulated. The molecular mass spectral data related to base molecule and substitutional group of the compound was analyzed. The modification of the chemical property by the reaction mechanism of the injection of dicarboxylic group in the base molecule was investigated. The 13C and 1H NMR spectra were simulated by using the gauge independent atomic orbital (GIAO) method and the absolute chemical shifts related to TMS were compared with experimental spectra. The study on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies, were performed by hybrid Gaussian calculation methods. The orbital energies of different levels of HOMO and LUMO were calculated and the molecular orbital lobe overlapping showed the inter charge transformation between the base molecule and ligand group. From the frontier molecular orbitals (FMO), the possibility of electrophilic and nucleophilic hit also analyzed. The NLO activity of the title compound related to Polarizability and hyperpolarizability were also discussed. The present molecule was fragmented with respect to atomic mass and the mass variation depends on the substitutions have also been studied.

  18. Application of higher harmonic control to hingeless rotor systems

    NASA Technical Reports Server (NTRS)

    Nguyen, Khanh; Chopra, Inderjit

    1990-01-01

    A comprehensive analytical formulation has been dveloped to predict the vibratory hub loads of a helicopter rotor system in forward flight. The analysis is used to calculate the optimal higher harmonic control inputs and associated actuator power required to minimize these hub loads. The present formulation is based on a finite element method in space and time. A nonlinear time domain, unsteady aerodynamic model is used to obtain the airloads, and the rotor induced inflow is calculated using a nonuniform inflow model. Predicted vibratory hub loads are correlated with experimental data obtained from a scaled model rotor. Results of a parametric study on a hingeless rotor show that blade flap, lag and torsion vibration characteristics, offset of blade center of mass from elastic axis, offset of elastic axis from quarter-chord axis, and blade thrust greatly affect the higher harmonic control actuator power requirement.

  19. Approximating coupled cluster level vibrational frequencies with composite methods.

    PubMed

    Fan, Yanping; Ho, Junming; Bettens, Ryan P A

    2006-03-01

    An extensive study of the harmonic frequencies of a large set of small polyatomic closed-shell molecules computed at both single level ab initio and composite approximations is presented here. Using various combinations of basis sets, composite methods are capable of predicting single level ab initio CCSD(T) harmonic frequencies to within 5 cm(-1) on average, which suggests a computationally affordable means of obtaining highly accurate vibrational frequencies compared to the CCSD(T) level. A general approach for calculating the composite level equilibrium geometries and harmonic frequencies for polyatomic systems that uses the Collin's method of interpolating potential energy surfaces is also described here. This approach is further tested on tetrafluoromethane, and an estimation of the potential CPU time savings that may be obtained is also presented. It is envisaged that the findings here will enable theoretical studies of fundamental frequencies and energetics of significantly larger molecular systems. PMID:16494391

  20. High-order harmonic generation from molecules

    NASA Astrophysics Data System (ADS)

    Wagner, Nicholas L.

    High harmonic generation in atoms is well understood in terms of the three step model (ionization, propagation and recombination), and much attention has been payed to the dynamics of the continuum electron in the propagation step. However, a molecular medium can be used to further understand the ionization and recombination steps. High harmonic generation can also be used to probe the dynamics of rotational and vibrational wave packets in molecular media. This thesis reports on two experiments using high harmonic generation from molecular media. In the first experiment, an impulsive Raman pump is used to excite a rotational wave packet in the molecular system, and a second time-delayed pulse generates high harmonics from the rotationally excited medium. Both the intensity and the phase of the high harmonic emission are measured. The general features of the orientational dipole are extracted from the phase and intensity modulations. A second experiment uses a vibrationally excited molecule as the high harmonic generation medium. The coherently excited molecular vibrations modulate the intensity of the high harmonic generation. Using high harmonic generation as a probe makes it possible to see all excited modes include two modes which were not present using a comparable visible probe. The rotational dephasing of the vibrational wave packet is also observed.

  1. FT-IR, FT-Raman spectra and ab initio HF and DFT calculations of 2-nitro- and 4-nitrobenzaldehydes

    Microsoft Academic Search

    S Kalaichelvan; N Sundaraganesan; B Dominic Joshua

    2008-01-01

    Combined experimental and theoretical studies on molecular and vibrational structure of 2-nitrobenzaldehyde and 4-nitrobenzaldehydes are reported. The Fourier transform infrared and Fourier transform Raman spectra of 2NB and 4NB has been recorded in the solid phase. The optimized geometry has been calculated by HF and B3LYP methods with 6-311++G(d,p) basis set. The harmonic vibrational frequencies of the title compounds have

  2. Femtosecond nonlinear spectroscopy at surfaces: Second-harmonic probing of hole burning at the Si(111)7x7 surface and fourier-transform sum-frequency vibrational spectroscopy

    SciTech Connect

    McGuire, John Andrew

    2004-11-24

    The high temporal resolution and broad bandwidth of a femtosecond laser system are exploited in a pair of nonlinear optical studies of surfaces. The dephasing dynamics of resonances associated with the adatom dangling bonds of the Si(111)7 x 7 surface are explored by transient second-harmonic hole burning, a process that can be described as a fourth-order nonlinear optical process. Spectral holes produced by a 100 fs pump pulse at about 800 nm are probed by the second harmonic signal of a 100 fs pulse tunable around 800 nm. The measured spectral holes yield homogeneous dephasing times of a few tens of femtoseconds. Fits with a Lorentzian spectral hole centered at zero probe detuning show a linear dependence of the hole width on pump fluence, which suggests that charge carrier-carrier scattering dominates the dephasing dynamics at the measured excitation densities. Extrapolation of the deduced homogeneous dephasing times to zero excitation density yields an intrinsic dephasing time of {approx} 70 fs. The presence of a secondary spectral hole indicates that scattering of the surface electrons with surface optical phonons at 570 cm{sup -1} occurs within the first 200 fs after excitation. The broad bandwidth of femtosecond IR pulses is used to perform IR-visible sum frequency vibrational spectroscopy. By implementing a Fourier-transform technique, we demonstrate the ability to obtain sub-laser-bandwidth spectral resolution. FT-SFG yields a greater signal when implemented with a stretched visible pulse than with a femtosecond visible pulse. However, when compared with multichannel spectroscopy using a femtosecond IR pulse but a narrowband visible pulse, Fourier-transform SFG is found to have an inferior signal-to-noise ratio. A mathematical analysis of the signal-to-noise ratio illustrates the constraints on the Fourier-transform approach.

  3. Vibrational predissociation of H5+

    NASA Astrophysics Data System (ADS)

    Špirko, Vladimír; Amano, Takayoshi; Kraemer, Wolfgang P.

    2006-06-01

    The full nine-dimensional vibrational Hamiltonian for H5+ described in the literature [Kraemer et al., J. Mol. Spectrosc. 164, 500 (1994)] is adopted here for an approximate evaluation of the spectral linewidths of the observed H-H stretching modes of the H5+ ion and the corresponding modes of its D5+ isotopomer. In this approximation the high dimensionality of the original Hamiltonian is reduced to a three-dimensional model Hamiltonian which takes only the H-H stretching modes and the molecular dissociation mode into consideration assuming that they are adiabatically separable from the remaining modes. To make the calculations numerically feasible, the molecular degenerate ("skeletal") vibrations are assumed to take place in harmonic potentials, and the effect of the internal propeller rotation is completely disregarded. The linewidths calculated in this approximation are too small to explain the broad shapes of the observed spectral transitions. It can thus be argued that the failure to resolve rotational structure in the observed bands is mainly due to spectral congestion and only partly due to predissociation of the H5+ cluster.

  4. First principle calculations of the electronic and vibrational properties of the 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole molecule.

    PubMed

    Makowska-Janusik, Malgorzata; Kajzar, Francois; Miniewicz, Andrzej; Mydlova, Lucia; Rau, Ileana

    2015-02-26

    Results of first principle quantum chemical calculations of electronic and vibrational properties of the push-pull 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP) molecule are reported and discussed. The structure of DCNP was optimized with HF/6-311G methodology and found to be planar. On the basis of obtained geometry, infrared absorption and Raman spectra were computed within the HF/6-311++G** formalism. They allow to conclude that the changes of molecule dipole moment and variation of its polarizability appear at the same vibrational mode and affect the optical properties of the DCNP. Four different methodologies: time-dependent HF and time-dependent DFT method with B3LYP, LC-BLYP, and CAM-B3LYP potentials were used to compute the optical absorption spectra of DCNP. Influence of solvent on molecular electronic structure was studied within the C-PCM model. It predicts the DFT/B3LYP methodology as the best one to compute the NLO properties of the DCNP. The computed HOMO and LUMO orbitals show evidence that the ground state of the molecule is located at its aromatic part. The discussion of charge transfer during the excitation process for the transition S0-S1 was performed. The charge transfer parameter calculated in vacuum and in solvent gives the evidence that the solvent environment weakly enhance the molecular charge transfer. It confirms the tendency of an occurrence of the intermolecular charge transfer in DCNP which is crucial for its hyperpolarizability magnitude. It was proved that the second-order susceptibility corresponding to SHG may be calculated for host-guest polymer/DCNP composite using the simple oriented gas model and the rigorous local field approach should not necessarily be applied. PMID:25648877

  5. The electronic origin and vibrational levels of the first excited singlet state of isocyanic acid (HNCO)

    NASA Astrophysics Data System (ADS)

    Berghout, H. Laine; Crim, F. Fleming; Zyrianov, Mikhail; Reisler, Hanna

    2000-04-01

    The combination of vibrationally mediated photofragment yield spectroscopy, which excites molecules prepared in single vibrational states, and multiphoton fluorescence spectroscopy, which excites molecules cooled in a supersonic expansion, provides detailed information on the energetics and vibrational structure of the first excited singlet state (S1) of isocyanic acid (HNCO). Dissociation of molecules prepared in individual vibrational states by stimulated Raman excitation probes vibrational levels near the origin of the electronically excited state. Detection of fluorescence from dissociation products formed by multiphoton excitation through S1 of molecules cooled in a supersonic expansion reveals the vibrational structure at higher energies. Both types of spectra show long, prominent progressions in the N-C-O bending vibration built on states with different amounts of N-C stretching excitation and H-N-C bending excitation. Analyzing the spectra locates the origin of the S1 state at 32 449±20 cm-1 and determines the harmonic vibrational frequencies of the N-C stretch (?3=1034±20 cm-1), the H-N-C bend (?4=1192±19 cm-1), and the N-C-O bend (?5=599±7 cm-1), values that are consistent with several ab initio calculations. The assigned spectra strongly suggest that the N-C stretching vibration is a promoting mode for internal conversion from S1 to S0.

  6. DENSITY FUNCTIONAL CALCULATION OF ENERGIES AND VIBRATIONAL FREQUENCIES OF GLUCOSE AND GLUCOSE-WATER COMPLEXES: WATER PLACEMENT AND GLUCOSE CONFORMATIONAL EFFECTS ON THE CALCULATED INFRARED SPECTRUM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The structures and energies of glucose and glucose monohydrates have been calculated at the B3LYP/6-311++G** level of theory. Both the alpha and beta anomers were studied, with all possible combinations of hydroxymethyl rotamer (gg, gt, or tg) and hydroxyl orientation (clockwise or counter-clockwis...

  7. Vibrational spectroscopic studies (FT-IR, FT-Raman) and quantum chemical calculations on 5-(Adamantan-1-yl)-3-[(4-fluoroanilino)methyl]-2,3-dihydro-1,3,4-oxadiazole-2-thione, a potential chemotherapeutic agent.

    PubMed

    Al-Abdullah, Ebtehal S; Sebastian, Sr S H Roseline; Al-Wabli, Reem I; El-Emam, Ali A; Panicker, C Yohannan; Van Alsenoy, Christian

    2014-12-10

    The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 5-(Adamantan-1-yl)-3-[(4-fluoroanilino)methyl]-2,3-dihydro-1,3,4-oxadiazole-2-thione are investigated experimentally and theoretically using Gaussian09 software package. Potential energy distribution of normal modes vibrations was done using GAR2PED program. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated geometrical parameters are in agreement with the XRD data. The calculated first hyperpolarizability is high and the title compound is an attractive candidate for further studies in non-linear optical applications. To estimate the chemical reactivity of the molecule, the molecular electrostatic potential is calculated for the optimized geometry of the molecule. PMID:24992920

  8. Ab initio molecular dynamics with noisy forces: validating the quantum Monte Carlo approach with benchmark calculations of molecular vibrational properties.

    PubMed

    Luo, Ye; Zen, Andrea; Sorella, Sandro

    2014-11-21

    We present a systematic study of a recently developed ab initio simulation scheme based on molecular dynamics and quantum Monte Carlo. In this approach, a damped Langevin molecular dynamics is employed by using a statistical evaluation of the forces acting on each atom by means of quantum Monte Carlo. This allows the use of an highly correlated wave function parametrized by several variational parameters and describing quite accurately the Born-Oppenheimer energy surface, as long as these parameters are determined at the minimum energy condition. However, in a statistical method both the minimization method and the evaluation of the atomic forces are affected by the statistical noise. In this work, we study systematically the accuracy and reliability of this scheme by targeting the vibrational frequencies of simple molecules such as the water monomer, hydrogen sulfide, sulfur dioxide, ammonia, and phosphine. We show that all sources of systematic errors can be controlled and reliable frequencies can be obtained with a reasonable computational effort. This work provides convincing evidence that this molecular dynamics scheme can be safely applied also to realistic systems containing several atoms. PMID:25416879

  9. Vibrational assignments, normal coordinate analysis, B3LYP calculations and conformational analysis of methyl-5-amino-4-cyano-3-(methylthio)-1H-pyrazole-1-carbodithioate

    NASA Astrophysics Data System (ADS)

    Mohamed, Tarek A.; Hassan, Ali M.; Soliman, Usama A.; Zoghaib, Wajdi M.; Husband, John; Hassan, Saber M.

    2011-09-01

    The Raman and infrared spectra of solid methyl-5-amino-4-cyano-3-(methylthio)-1H-pyrazole-1-carbodithioate (MAMPC, C 7H 8N 4S 3) were measured in the spectral range of 3700-100 cm -1 and 4000-200 cm -1 with a resolution of 4 and 0.5 cm -1, respectively. Room temperature 13C NMR and 1H NMR spectra from room temperature down to -60 °C were also recorded. As a result of internal rotation around C-N and/or C-S bonds, eighteen rotational isomers are suggested for the MAMPC molecule (Cs symmetry). DFT/B3LYP and MP2 calculations were carried out up to 6-311++G(d,p) basis sets to include polarization and diffusion functions. The results favor conformer 1 in the solid (experimentally) and gaseous (theoretically) phases. For conformer 1, the two -CH 3 groups are directed towards the nitrogen atoms (pyrazole ring) and C dbnd S, while the -NH 2 group retains sp 2 hybridization and C-C tbnd N bond is quasi linear. To support NMR spectral assignments, chemical shifts ( ?) were predicted at the B3LYP/6-311+G(2d,p) level using the method of Gauge-Invariant Atomic Orbital (GIAO) method. Moreover, the solvent effect was included via the Polarizable Continuum Model (PCM). Additionally, both infrared and Raman spectra were predicted using B3LYP/6-31G(d) calculations. The recorded vibrational, 1H and 13C NMR spectral data favors conformer 1 in both the solid phase and in solution. Aided by normal coordinate analysis and potential energy distributions, confident vibrational assignments for observed bands have been proposed. Moreover, the CH 3 barriers to internal rotations were investigated. The results are discussed herein are compared with similar molecules whenever appropriate.

  10. Computing the classical mechanical vibrational echo with the fluctuating frequency approximation

    NASA Astrophysics Data System (ADS)

    Williams, Ryan B.; Loring, Roger F.

    2000-12-01

    The vibrational photon echo is an infrared nonlinear spectroscopic measurement probing the time scales of dynamical processes that underlie a linear absorption spectrum. The challenges posed by the quantum mechanical treatment of large anharmonic systems motivate the consideration of this observable within classical mechanics. The rigorous calculation of the classical mechanical vibrational echo requires going beyond a conventional molecular dynamics simulation of trajectories to propagate stability matrix elements, which quantify the sensitivity of classical trajectories to small changes in initial conditions. As an alternative to this procedure, we present an approximate theory of the vibrational echo that avoids the numerical calculation of stability matrix elements. This approach, the fluctuating frequency approximation (FFA), generalizes a well established treatment of linear spectroscopy that models a driven anharmonic oscillator as a harmonic system with a fluctuating frequency. The FFA compares well with numerically exact calculations of the echo for a solvated anharmonic oscillator.

  11. Ab initio and DFT studies of the structure and vibrational spectra of anhydrous caffeine

    NASA Astrophysics Data System (ADS)

    Srivastava, Santosh K.; Singh, Vipin B.

    2013-11-01

    Vibrational spectra and molecular structure of anhydrous caffeine have been systematically investigated by second order Moller-Plesset (MP2) perturbation theory and density functional theory (DFT) calculations. Vibrational assignments have been made and many previous ambiguous assignments in IR and Raman spectra are amended. The calculated DFT frequencies and intensities at B3LYP/6-311++G(2d,2p) level, were found to be in better agreement with the experimental values. It was found that DFT with B3LYP functional predicts harmonic vibrational wave numbers more close to experimentally observed value when it was performed on MP2 optimized geometry rather than DFT geometry. The calculated TD-DFT vertical excitation electronic energies of the valence excited states of anhydrous caffeine are found to be in consonance to the experimental absorption peaks.

  12. Raman spectrum, quantum mechanical calculations and vibrational assignments of (95% alpha-TeO2/5% Sm2O3) glass.

    PubMed

    Shaltout, I; Mohamed, Tarek A

    2007-06-01

    Chozen system of tellurite glasses doped with rare earth oxides (95% alpha-TeO(2)+5% Sm2O3) was prepared by melt quenching. Consequently, the Raman spectrum (150-1250 cm(-1)) of the modified tellurite have been recorded. As a continuation to our normal coordinate analysis, force constants and quantum mechanical (QM) calculations for tbp TeO4(4-) (triagonal bipyramid, C(2v)) and TeO(3+1); Te2O7(6-) (bridged tetrahedral), we have carried out ab initio frequency calculations for tpy TeO3(2-) (triagonal pyramidal, C(3v) and C(s)) and tp TeO3(2-) (triagonal planar, D(3h)) ions. The quantum mechanical calculations at the levels of RHF, B3LYP and MP2 allow confident vibrational assignments and structural identification in the binary oxide glass (95% alpha-TeO2 +5% Sm2O3). The dominant three-dimensional network structures in the modified glass are triagonal pyramidal TeO3 with minor features of short range distorted tbp TeO4 and bridged tetrahedral unit of TeO(3+1), leading to a structure of infinite chain. Therefore, alpha-TeO2/Sm2O3 (95/5%) glass experience structural changes from TeO4 (tbp); Te2O7 (TeO(3+1))-->TeO3 (tpy). PMID:16982208

  13. Cross sections and rate constants for low-temperature 4HeH2 vibrational relaxation

    Microsoft Academic Search

    Millard H. Alexander; Paul McGuire

    1976-01-01

    Converged coupled-states integral cross sections were determined for the vibrational relaxation of the v=1 j=0 level of p-H2 in collisions with 4He. The collision energies ranged from 0.005 to 0.4 eV. The Gordon-Secrest (GS) potential was used with both a harmonic (HO) and rotating-Morse oscillator (MO) description of the H2 molecule. Additional calculations incorporated modifications in the long-range and spherically

  14. Vibrational spectrum, ab initio calculations, conformational stabilities and assignment of fundamentals of the Ci conformer of 1,4-dichlorobutane.

    PubMed

    LaPlante, Arthur J; Stidham, Howard D

    2008-11-15

    The infrared and Raman spectrum of 1,4-dichlorobutane is reported in solid, liquid and gas. Ab initio calculations for the nine stable or metastable conformers of 1,4-dichlorobutane are reported for Moller-Ploessett second order electron correlation and B3LYP density functionals with a variety of basis sets, using approximations as high as 6-311+g(2d, 2p). Normal coordinate calculations were conducted for the nine conformers and the results used to provide assignments for some of the observed infrared and Raman bands. An attempt to use the assignments together with the ab initio intensities or Raman activities to investigate the composition of the liquid at room temperature proved modestly successful, and suggested that the populations are altered from those expected in the gas phase by interactions of the permanent electric dipole moments with the dipolar plasma in which the conformers are immersed in the liquid. A substantial disagreement between the Moeller-Ploessett and density functional results is reported, and the calculation of intensities and activities is insufficiently accurate to allow detailed interpretation of the spectrum of the room temperature liquid. A complete assignment of fundamentals is given for the conformer of Ci symmetry, and one Raman and one infrared band is identified with the C2h conformer. All the other infrared and Raman bands in the liquid or the gas are composites of several contributors. PMID:18325830

  15. Theoretical structures and experimental vibrational spectra of isomeric benzofused thieno [3,2- b] furan compounds

    NASA Astrophysics Data System (ADS)

    Ledesma, A. E.; Contreras, C.; Svoboda, J.; Vektariane, A.; Brandán, S. A.

    2010-04-01

    A theoretical structural and experimental vibrational study for the benzothieno [3,2- b] furan and thieno [3,2- b] benzofuran compounds is presented. The density functional theory (DFT) has been used to study its structures and vibrational properties. The geometries were fully optimised at the B3LYP/6-31G? and B3LYP/6-311++G?? levels of theory and the harmonic vibrational frequencies were evaluated at the same levels. The calculated harmonic vibrational frequencies for the compound are consistent with the experimental IR spectrum in chloroform solution. These calculations gave us precise knowledge of the normal modes of vibration of these compounds. A complete assignment of all the observed bands in the infrared and Raman spectra for both benzothieno [3,2- b] furans compound was performed. The nature of the different rings bonds in both compounds was quantitatively investigated by means of Natural Bond Orbital (NBO) analysis. The topological properties of electronic charge density are analysed by employing Bader's Atoms in the Molecules theory (AIM).

  16. Principal Trajectories of Forced Vibrations

    Microsoft Academic Search

    Valery Pilipchuk

    \\u000a As shown earlier by Zhuravlev (1992) that harmonically loaded linear conservative systems possess an alternative physically\\u000a reasonable basis, which is generally different from that associated with conventional principal coordinates. Briefly, such\\u000a a basis determines directions of harmonic loads along which the system response is equivalent to a single oscillator. The\\u000a corresponding definition (principal directions of forced vibrations) is loosing sense

  17. Ultrafast infrared spectroscopy of riboflavin: dynamics, electronic structure, and vibrational mode analysis.

    PubMed

    Wolf, Matthias M N; Schumann, Christian; Gross, Ruth; Domratcheva, Tatiana; Diller, Rolf

    2008-10-23

    Femtosecond time-resolved infrared spectroscopy was used to study the vibrational response of riboflavin in DMSO to photoexcitation at 387 nm. Vibrational cooling in the excited electronic state is observed and characterized by a time constant of 4.0 +/- 0.1 ps. Its characteristic pattern of negative and positive IR difference signals allows the identification and determination of excited-state vibrational frequencies of riboflavin in the spectral region between 1100 and 1740 cm (-1). Density functional theory (B3LYP), Hartree-Fock (HF) and configuration interaction singles (CIS) methods were employed to calculate the vibrational spectra of the electronic ground state and the first singlet excited pipi* state as well as respective electronic energies, structural parameters, electronic dipole moments and intrinsic force constants. The harmonic frequencies of the S 1 excited state calculated by the CIS method are in satisfactory agreement with the observed band positions. There is a clear correspondence between computed ground- and excited-state vibrations. Major changes upon photoexcitation include the loss of the double bond between the C4a and N5 atoms, reflected in a downshift of related vibrations in the spectral region from 1450 to 1720 cm (-1). Furthermore, the vibrational analysis reveals intra- and intermolecular hydrogen bonding of the riboflavin chromophore. PMID:18821792

  18. Structural and vibrational investigation on species derived from the cyclamic acid in aqueous solution by using HATR and Raman spectroscopies and SCRF calculations

    NASA Astrophysics Data System (ADS)

    Brizuela, Alicia B.; Raschi, Ana B.; Castillo, María V.; Davies, Lilian; Romano, Elida; Brandán, Silvia A.

    2014-09-01

    In this study, aqueous solutions at different molar concentrations of sodium cyclamate in water were completely characterized by HATR (Horizontal Attenuated Total Reflectance) and Raman spectroscopies. The theoretical structures of cyclamate ion, the zwitterionic and neutral forms of the cyclamic acid and its dimer were optimized in gas and aqueous solution phases by using the hybrid B3LYP/6-31G* method. The solvent effects for the four species in aqueous solutions were simulated by using self-consistent reaction field (SCRF) calculations employing the integral equation formalism variant (IEFPCM) model. The complete assignments of the vibrational spectra of all the forms of cyclamic acid were performed taking into account the factor group analysis with the Scaled Quantum Mechanics Force Field (SQMFF) methodology. The existence of the zwitterionic and neutral forms of the cyclamic acid and its dimer in a solution of cyclamate in water is evidenced by characteristic bands in the HATR and Raman spectra. The dimerization of cyclamate in aqueous solution was previously reported by conductimetric method. The natural population analysis (NPA) and Merz-Kollman (MK) charges, molecular electrostatic potential (MEP), natural bond orbital (NBO) and atoms in molecules (AIM) calculations predict for all the species the principal donor and acceptor sites for the H bonds formation in aqueous solution. The SQM force fields for the cyclamate ion, the zwitterionic and neutral species of the cyclamic acid were obtained and their corresponding force constants in both phases were reported. Additionally, the solvation energies for those species were reported.

  19. Quantum-Chemical Calculations of Radial Functions for Rotational and Vibrational g Factors, Electric Dipolar Moment and Adiabatic Corrections to the Potential Energy for Analysis of Spectra of HeH +

    Microsoft Academic Search

    Stephan P. A. Sauer; Hans Jørgen Aa. Jensen; John F. Ogilvie

    2005-01-01

    Computational spectrometry, which implies an interaction between quantum chemistry and analysis of molecular spectra to derive accurate information about molecular properties, is needed for the analysis of the pure rotational and vibration–rotational spectra of HeH+ in four isotopic variants to obtain precise values of equilibrium internuclear distance and force coefficient. For this purpose, we have calculated the electronic energy, rotational

  20. A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers

    NASA Astrophysics Data System (ADS)

    Powell, B. J.; Baruah, T.; Bernstein, N.; Brake, K.; McKenzie, Ross H.; Meredith, P.; Pederson, M. R.

    2004-05-01

    We report first-principles density-functional calculations for hydroquinone (HQ), indolequinone (IQ), and semiquinone (SQ). These molecules are believed to be the basic building blocks of the eumelanins, a class of biomacromolecules with important biological functions (including photoprotection) and with the potential for certain bioengineering applications. We have used the difference of self-consistent fields method to study the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, ?HL. We show that ?HL is similar in IQ and SQ, but approximately twice as large in HQ. This may have important implications for our understanding of the observed broadband optical absorption of the eumelanins. The possibility of using this difference in ?HL to molecularly engineer the electronic properties of eumelanins is discussed. We calculate the infrared and Raman spectra of the three redox forms from first principles. Each of the molecules have significantly different infrared and Raman signatures, and so these spectra could be used in situ to nondestructively identify the monomeric content of macromolecules. It is hoped that this may be a helpful analytical tool in determining the structure of eumelanin macromolecules and hence in helping to determine the structure-property-function relationships that control the behavior of the eumelanins.

  1. Vibration manual

    NASA Technical Reports Server (NTRS)

    Green, C.

    1971-01-01

    Guidelines of the methods and applications used in vibration technology at the MSFC are presented. The purpose of the guidelines is to provide a practical tool for coordination and understanding between industry and government groups concerned with vibration of systems and equipments. Topics covered include measuring, reducing, analyzing, and methods for obtaining simulated environments and formulating vibration specifications. Methods for vibration and shock testing, theoretical aspects of data processing, vibration response analysis, and techniques of designing for vibration are also presented.

  2. Chaotic Vibrations of a Clamped-Supported Beam with a Concentrated Mass Subjected to Static Axial Compression and Periodic Lateral Acceleration

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Dai; Nagai, Ken-Ichi; Maruyama, Shinichi

    Experimental results and analytical results are presented on chaotic vibrations of a clamped-supported beam with a concentrated mass. The beam is elastically compressed by an axial spring at the simply supported end and is excited by lateral periodic acceleration. In the experiment, periodic and chaotic vibrations are detected under several conditions of the axial compression. In the analysis, the governing equation is reduced to nonlinear differential equations of a multiple-degree-of-freedom system by the Galerkin procedure. The nonlinear periodic responses are calculated by the harmonic balance method. The chaotic responses are numerically integrated by the Runge-Kutta-Gill method. The chaotic responses of the beam are examined with the Fourier spectra, the Poincaré projections and the maximum Lyapunov exponents and the principal component analysis. Under a specific axial compression with post-buckled state of the beam, the chaotic vibrations dominated by dynamic snap-through are generated by the ultra-sub-harmonic resonance response of 2/3order of the fundamental vibration mode. The number of pre-dominant vibration modes that contribute to the chaos is found to be three. Decreasing the axial compression, the chaotic vibrations are induced by the internal resonance response between the second and the fundamental mode of vibration. The number of predominant vibration modes that contribute to the chaos is found to be two or three. Both results of the experimental and the analysis agree remarkably with each other in detail.

  3. A vibrational molecular force field of model compounds with biological interest. V. Harmonic dynamic of N-acetyl-?- D-glucosamine in the crystalline state

    NASA Astrophysics Data System (ADS)

    Kouach-Alix, I.; Vergoten, G.

    1994-07-01

    Combining the modified Urey—Bradley—Shimanouchi intramolecular potential energy function with an appropriate intermolecular energy function, normal coordinate calculations have been performed for N-acetyl-?- D-glucosamine in the crystalline state. The infrared spectra in the mid range (4000-500 cm -1) and the Raman spectra in 3500-20 cm -1 range were recorded. The overall agreement between the observed and calculated frequencies led to an average error of the order of 3.5 cm -1. The computed potential energy distribution was found to be compatible with previous assignments of D-glucose and D-galactose for the pyranose ring and for N-methylacetamide for the acetamido group. The set of force constants used for N-acetyl-?- D-glucosamine was approximately the same as that obtained for the glucose and N-methylacetamide respectively for the pyranose ring and the acetamido group, a difference existing only for the atoms involved in the anomeric and hydroxy groups.

  4. Direct calculations of vibrational absorption and circular dichroism spectra of alanine dipeptide analog in water: quantum mechanical/molecular mechanical molecular dynamics simulations.

    PubMed

    Yang, Seongeun; Cho, Minhaeng

    2009-10-01

    The vibrational absorption (IR) and vibrational circular dichroism (VCD) spectra of alanine dipeptide analog in water are directly calculated by Fourier transforming the time correlation functions of the electric and magnetic dipole moments, which are calculated using the dynamic partial charges and trajectory of the peptide generated from the quantum mechanical/molecular mechanical molecular dynamics simulations. The alanine dipeptide analog is treated at the Hartree-Fock level with 3-21G, 4-31G, 6-31G, and 6-31G(*) basis sets and the solvent H(2)O is modeled with the TIP3P water. The atomic partial charges are obtained from the Lowdin population analysis, which gives consistent IR spectral profiles irrespective of the basis sets used. The simulated VCD spectrum by a polyproline II(P(II))-dominant trajectory is compatible with the previous experimental results of the polyproline peptides, where the amide I and II VCD bands are negative couplets with a weak positive peak to the high frequency region. The sampling efficiency of the P(II) conformer is much lower than the other ones at all basis levels used. The simulated VCD spectrum of alpha-helix averaged over five trajectories has the reverse sign pattern compared to the P(II) spectrum and is found to be consistent with the previously observed spectral features of alpha-helical polypeptides. The sign patterns of the beta-strand VCD spectrum are qualitatively similar to the experimental spectra of beta-sheet rich proteins. The VCD spectra obtained from the trajectories containing several extended conformers such as beta and P(II) are not clearly distinguishable from the beta-strand-dominant spectra. It is interesting that the P(II) and the coil VCD spectra coincide in sign pattern and relative intensity for all amide modes. This demonstrates that the negative couplet structures of the amide I and II VCD spectra do not necessarily prove the dominance of either P(II) or coil conformation. We anticipate that the present method can be used to directly simulate the IR and VCD spectra of structurally heterogeneous biomolecules in condensed phases. PMID:19814574

  5. Harmonic Generation

    Microsoft Academic Search

    H. J. Scott; L. J. Black

    1938-01-01

    When plate current in a vacuum-tube amplifier flows for only a portion of the grid-excitation cycle, harmonics appear in the output circuit. The magnitude of any one of these harmonics depends upon the fraction of the fundamental cycle during which plate current flows. In the gradual transition from perfect class A to extreme class C operation, the magnitude of the

  6. Vibrational contribution to molecular polarizabilities and hyperpolarizabilities

    NASA Astrophysics Data System (ADS)

    Pandey, P. K. K.; Santry, D. P.

    1980-09-01

    The vibrational averaging theory of Kern and Matcha is extended, at the harmonic level of approximation, to the case where the molecular property under investigation can itself lead indirectly to a perturbation of the vibrational levels of the molecule. It is found that contributions arising from this perturbation can be significant, especially for molecular hyperpolarizabilities.

  7. Molecular structural, non-linear optical, second order perturbation and Fukui studies of Indole-3-Aldehyde using density functional calculations.

    PubMed

    Muthu, S; Maheswari, J Uma; Sundius, Tom

    2013-04-01

    Indole-3-Aldehyde is a new organic non-linear material having good second harmonic generation. The optimized molecular geometry, harmonic vibrational frequencies, infrared intensities of Indole-3-Aldehyde (I3A, C9H7NO) in the ground state were carried out by using density functional theory (B3LYP) method with 6-31G(d,p) basis set. A detailed interpretation of the infrared spectrum of Indole-3-Aldehyde is reported. The vibrational frequencies are calculated and compared with experimental FT-IR spectra. The theoretical spectrograms of FT-IR of the title compound have been constructed in addition, theoretical information like ONIOM, potential energy surface, NBO, and Fukui function are also calculated. Unambiguous vibrational assignment of all the fundamentals was made using the potential energy distribution. PMID:23416887

  8. Molecular structural, non-linear optical, second order perturbation and Fukui studies of Indole-3-Aldehyde using density functional calculations

    NASA Astrophysics Data System (ADS)

    Muthu, S.; Uma Maheswari, J.; Sundius, Tom

    2013-04-01

    Indole-3-Aldehyde is a new organic non-linear material having good second harmonic generation. The optimized molecular geometry, harmonic vibrational frequencies, infrared intensities of Indole-3-Aldehyde (I3A, C9H7NO) in the ground state were carried out by using density functional theory (B3LYP) method with 6-31G(d,p) basis set. A detailed interpretation of the infrared spectrum of Indole-3-Aldehyde is reported. The vibrational frequencies are calculated and compared with experimental FT-IR spectra. The theoretical spectrograms of FT-IR of the title compound have been constructed in addition, theoretical information like ONIOM, potential energy surface, NBO, and Fukui function are also calculated. Unambiguous vibrational assignment of all the fundamentals was made using the potential energy distribution.

  9. Vibrational spectra, crystal structure, DFT quantum chemical calculations and conformation of the hydrazo - bond in 6-methyl-3-nitro-2-(2-phenylhydrazinyl)pyridine

    NASA Astrophysics Data System (ADS)

    Kucharska, E.; Michalski, J.; S?siadek, W.; Talik, Z.; Bryndal, I.; Hanuza, J.

    2013-04-01

    The crystal and molecular structures of 6-methyl-3-nitro-2-(2-phenylhydrazinyl)pyridine (6-methyl-3-nitro-2-phenylhydrazopyridine) have been determined by X-ray diffraction and quantum chemical DFT analysis. The crystal is monoclinic, space group C2/c, with Z = 8 formula units in the elementary unit cell of dimensions a = 16.791(4), b = 6.635(2), c = 21.704(7) Å, ? = 100.54(3)°. The molecule consists of two nearly planar pyridine subunits. A conformation of the linking hydrazo-bridge Csbnd NHsbnd NHsbnd C is bend and the dihedral angle between the planes of the phenyl and pyridine rings is 88.2(5)°. The hydrogen bonding of the type Nsbnd H···N and possibly also Csbnd H···O favors a dimer formation in the crystal structure. The dimers are further linked by a Nsbnd H···O hydrogen bond, so forming a layer parallel to the ab plane. The molecular structure of the studied compound has been determined using the DFT B3LYP/6-311G(2d,2p) approach and compared to that derived from X-ray studies. The IR and Raman wavenumbers have been calculated for the optimized geometry of a possible monomer structural model but the possibility of the dimer formation through the Nsbnd H···N hydrogen bond has also been considered. The structural and vibrational properties of the intra-molecular Nsbnd H···O interaction are described.

  10. Stator current-based sensorless vibration monitoring of induction motors

    Microsoft Academic Search

    Caryn M. Riley; Brian K. Lin; Thomas G. Habetler; Gerald B. Kliman

    1997-01-01

    This paper presents an initial study into the relationship between vibration and current harmonics of electric motors, including the effect of externally induced vibrations. This relationship was investigated experimentally on both new motors, on a vibration stand and on a motor with berating wear. Both theory and experimental results show that a change in the RMS value of the stator

  11. The Effect of Anharmonicity on Diatomic Vibration; A Spreadsheet Simulation

    NSDL National Science Digital Library

    Instructors and students can use this spreadsheet to quickly and easily observe how the shape of a one-dimensional vibrational potential energy curve and its associated vibrational quantum energy levels depend on the anharmonicity. This illustrates the connection between the harmonic (approximation) and anharmonic descriptions of molecular vibrations.

  12. Calculation of the vibrational temperatures and populations of the laser-active levels of CO{sub 2} from the spectral distribution of the gain

    SciTech Connect

    Arshinov, K I [Institute of Technical Acoustics, Academy of Sciences of Belarus, Vitebsk (Belarus); Leshenyuk, N S [A.D. Sakharov International Institute for Radioecology, Minsk (Belarus); Nevdakh, Vladimir V [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

    1998-08-31

    The gains measured at the centres of vibrational - rotational lines of the main bands of the CO{sub 2} molecule were used to determine, by the least-squares method, the populations of the laser-active levels and the vibrational temperatures of the active medium of a cw electric-discharge CO{sub 2} laser. (lasers, active media)

  13. Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations.

    PubMed

    Hetma?czyk, Joanna; Hetma?czyk, Lukasz; Migda?-Mikuli, Anna; Mikuli, Edward

    2014-10-24

    The vibrational and reorientational motions of NH3 ligands and ClO4(-) anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385cm(-1), associated with: ?r(NH3) and ?as(N-H) modes, respectively, indicate that there exist fast (correlation times ?R?10(-12)-10(-13)s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5kJmol(-1), in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TC(c)=137.6K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311+G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6](2+) cation and ClO4(-) anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models. PMID:25459713

  14. Investigation of a vibration-damping unit for reduction in low-frequency vibrations of electric motors

    NASA Technical Reports Server (NTRS)

    Grigoryey, N. V.; Fedorovich, M. A.

    1973-01-01

    The vibroacoustical characteristics of different types of electric motors are discussed. It is shown that the basic source of low frequency vibrations is rotor unbalance. A flexible damping support, with an antivibrator, is used to obtain the vibroacoustical effect of reduction in the basic harmonic of the electric motor. A model of the electric motor and the damping apparatus is presented. Mathematical models are developed to show the relationships of the parameters. The basic purpose in using a calculation model id the simultaneous replacement of the exciting force created by the rotor unbalance and its inertial rigidity characteristics by a limiting kinematic disturbance.

  15. Correlated ab initio harmonic frequencies and infrared intensities for furan, pyrrole, and thiophene

    SciTech Connect

    Simandiras, E.D.; Handy, N.C.; Amos, R.D.

    1988-04-07

    Equilibrium geometries, harmonic vibrational frequencies, and infrared intensities are calculated analytically at the second-order Moeller-Plesset level (MP2) with a DZP basis for the five-membered heterocyclic aromatics furan, pyrrole, and thiophene. The results are of an accuracy to show up misassignments in the original experimental interpretation of the spectra. They also give confidence that ab initio calculations including electron correlation and using flexible basis sets can describe accurately the quadratic part of the potential energy surface. For such systems, these ab initio studies will aid the spectroscopic determination of force constants.

  16. Structure and vibrational analysis of methyl 3-amino-2-butenoate

    NASA Astrophysics Data System (ADS)

    Berenji, Ali Reza; Tayyari, Sayyed Faramarz; Rahimizadeh, Mohammad; Eshghi, Hossein; Vakili, Mohammad; Shiri, Ali

    2013-02-01

    The molecular structure and vibrational spectra of methyl 3-(amino)-2-butenoate (MAB) and its deuterated analogous, D3MAB, were investigated using density functional theory (DFT) calculations. The geometrical parameters and harmonic vibrational wavenumbers of MAB and D3MAB were obtained at the B3LYP/6-311++G(d,p) level. The calculated vibrational wavenumbers were compared with the corresponding experimental results. The assignment of the IR and Raman spectra of MAB and D3MAB was facilitated by calculating the anharmonic wavenumbers at the B3LYP/6-311G(d,p) level as well as recording and calculating the MAB spectra in CCl4 solution. The assigned normal modes were compared with a similar molecule, 4-amino-3-penten-2-one (APO). The theoretical results were in good agreement with the experimental data. All theoretical and experimental results indicate that substitution of a methyl group with a methoxy group considerably weakens the intramolecular hydrogen bond and reduces the ?-electron delocalization in the chelated ring system. The IR spectra also indicate that in the solid state, MAB is not only engaged in an intramolecular hydrogen bond, but also forms an intermolecular hydrogen bond. However, the intermolecular hydrogen bond will be removed in dilute CCl4 solution.

  17. Molecular structure, vibrational spectroscopy, NBO and HOMO, LUMO studies of o-methoxybenzonitrile.

    PubMed

    Elanthiraiyan, M; Jayasudha, B; Arivazhagan, M

    2015-01-01

    In the present study, the FT-IR and FT-Raman spectra of o-methoxybenzonitrile (O-MBN) have been recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The fundamental modes of vibrational frequencies of O-MBN are assigned. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of ab initio Hartree-Fock (HF) and density functional theory (DFT) gradient calculations with complete relaxation in the potential energy surface using 6-311++G(d,p) basis set. The vibrational frequencies which were determined experimentally from the spectral data are compared with those obtained theoretically from ab initio and DFT calculations. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors. The infrared and Raman spectra were also predicted from the calculated intensities. Thermodynamic properties like entropy, heat capacity, zero point energy, have been calculated for the molecule. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good non-linear optical (NLO) behavior. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization have been analyzed using natural bond orbitals (NBO) analysis. Unambiguous vibrational assignment of all the fundamentals was made using the total energy distribution (TED). PMID:25058575

  18. Coupled rotor/fuselage dynamic analysis of the AH-1G helicopter and correlation with flight vibrations data

    NASA Technical Reports Server (NTRS)

    Corrigan, J. C.; Cronkhite, J. D.; Dompka, R. V.; Perry, K. S.; Rogers, J. P.; Sadler, S. G.

    1989-01-01

    Under a research program designated Design Analysis Methods for VIBrationS (DAMVIBS), existing analytical methods are used for calculating coupled rotor-fuselage vibrations of the AH-1G helicopter for correlation with flight test data from an AH-1G Operational Load Survey (OLS) test program. The analytical representation of the fuselage structure is based on a NASTRAN finite element model (FEM), which has been developed, extensively documented, and correlated with ground vibration test. One procedure that was used for predicting coupled rotor-fuselage vibrations using the advanced Rotorcraft Flight Simulation Program C81 and NASTRAN is summarized. Detailed descriptions of the analytical formulation of rotor dynamics equations, fuselage dynamic equations, coupling between the rotor and fuselage, and solutions to the total system of equations in C81 are included. Analytical predictions of hub shears for main rotor harmonics 2p, 4p, and 6p generated by C81 are used in conjunction with 2p OLS measured control loads and a 2p lateral tail rotor gearbox force, representing downwash impingement on the vertical fin, to excite the NASTRAN model. NASTRAN is then used to correlate with measured OLS flight test vibrations. Blade load comparisons predicted by C81 showed good agreement. In general, the fuselage vibration correlations show good agreement between anslysis and test in vibration response through 15 to 20 Hz.

  19. Raman and IR studies and DFT calculations of the vibrational spectra of 2,4-Dithiouracil and its cation and anion.

    PubMed

    Singh, R; Yadav, R A

    2014-09-15

    Raman and FTIR spectra of solid 2,4-Dithiouracil (DTU) at room temperature have been recorded. DFT calculations were carried out to compute the optimized molecular geometries, GAPT charges and fundamental vibrational frequencies along with their corresponding IR intensities, Raman activities and depolarization ratios of the Raman bands for the neutral DTU molecule and its cation (DTU+) and anion (DTU-) using the Gaussian-03 software. Addition of one electron leads to increase in the atomic charges on the sites N1 and N3 and decrease in the atomic charges on the sites S8 and S10. Due to ionization of DTU molecule, the charge at the site C6 decreases in the cationic and anionic radicals of DTU as compared to its neutral species. As a result of anionic radicalization, the C5C6 bond length increases and loses its double bond character while the C4C5 bond length decreases. In the case of the DTU+ ion the IR and Raman band corresponding to the out-of-phase coupled NH stretching mode is strongest amongst the three species. The anionic DTU radical is found to be the most stable. The two NH out-of-plane bending modes are found to originate due to out-of-phase and in-phase coupling of the two NH bonds in the anion and cation contrary to the case of the neutral DTU molecule in which the out-of-plane bending motions of the two NH bonds are not coupled. PMID:24785092

  20. Raman and IR studies and DFT calculations of the vibrational spectra of 2,4-Dithiouracil and its cation and anion

    NASA Astrophysics Data System (ADS)

    Singh, R.; Yadav, R. A.

    2014-09-01

    Raman and FTIR spectra of solid 2,4-Dithiouracil (DTU) at room temperature have been recorded. DFT calculations were carried out to compute the optimized molecular geometries, GAPT charges and fundamental vibrational frequencies along with their corresponding IR intensities, Raman activities and depolarization ratios of the Raman bands for the neutral DTU molecule and its cation (DTU+) and anion (DTU-) using the Gaussian-03 software. Addition of one electron leads to increase in the atomic charges on the sites N1 and N3 and decrease in the atomic charges on the sites S8 and S10. Due to ionization of DTU molecule, the charge at the site C6 decreases in the cationic and anionic radicals of DTU as compared to its neutral species. As a result of anionic radicalization, the C5sbnd C6 bond length increases and loses its double bond character while the C4sbnd C5 bond length decreases. In the case of the DTU+ ion the IR and Raman band corresponding to the out-of-phase coupled Nsbnd H stretching mode is strongest amongst the three species. The anionic DTU radical is found to be the most stable. The two NH out-of-plane bending modes are found to originate due to out-of-phase and in-phase coupling of the two NH bonds in the anion and cation contrary to the case of the neutral DTU molecule in which the out-of-plane bending motions of the two NH bonds are not coupled.

  1. Potential-dependent chemisorption of carbon monoxide on platinum electrodes: new insight from quantum-chemical calculations combined with vibrational spectroscopy

    Microsoft Academic Search

    Sally A. Wasileski

    2001-01-01

    Density functional theory (DFT) using the finite cluster approach is utilized to compute binding energies, bond geometries, and vibrational properties of carbon monoxide adsorbed on Pt(111) as a function of the external interfacial field, focusing attention on the metal–CO bond itself. Comparison with electrode potential-dependent frequencies for the metal–CO (?M–CO) as well as the much-studied intramolecular C?O (?CO) vibration, as

  2. Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers

    NASA Astrophysics Data System (ADS)

    Fedorov, Dmitry A.; Derevianko, Andrei; Varganov, Sergey A.

    2014-05-01

    We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X1?+ electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-? basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-? quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm-1 for LiNa and by no more than 114 cm-1 for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm-1, and the discrepancies for the anharmonic correction are less than 0.1 cm-1. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.

  3. Accurate potential energy, dipole moment curves, and lifetimes of vibrational states of heteronuclear alkali dimers

    SciTech Connect

    Fedorov, Dmitry A.; Varganov, Sergey A., E-mail: svarganov@unr.edu [Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0216 (United States); Derevianko, Andrei [Department of Physics, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0220 (United States)] [Department of Physics, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557-0220 (United States)

    2014-05-14

    We calculate the potential energy curves, the permanent dipole moment curves, and the lifetimes of the ground and excited vibrational states of the heteronuclear alkali dimers XY (X, Y = Li, Na, K, Rb, Cs) in the X{sup 1}?{sup +} electronic state using the coupled cluster with singles doubles and triples method. All-electron quadruple-? basis sets with additional core functions are used for Li and Na, and small-core relativistic effective core potentials with quadruple-? quality basis sets are used for K, Rb, and Cs. The inclusion of the coupled cluster non-perturbative triple excitations is shown to be crucial for obtaining the accurate potential energy curves. A large one-electron basis set with additional core functions is needed for the accurate prediction of permanent dipole moments. The dissociation energies are overestimated by only 14 cm{sup ?1} for LiNa and by no more than 114 cm{sup ?1} for the other molecules. The discrepancies between the experimental and calculated harmonic vibrational frequencies are less than 1.7 cm{sup ?1}, and the discrepancies for the anharmonic correction are less than 0.1 cm{sup ?1}. We show that correlation between atomic electronegativity differences and permanent dipole moment of heteronuclear alkali dimers is not perfect. To obtain the vibrational energies and wave functions the vibrational Schrödinger equation is solved with the B-spline basis set method. The transition dipole moments between all vibrational states, the Einstein coefficients, and the lifetimes of the vibrational states are calculated. We analyze the decay rates of the vibrational states in terms of spontaneous emission, and stimulated emission and absorption induced by black body radiation. In all studied heteronuclear alkali dimers the ground vibrational states have much longer lifetimes than any excited states.

  4. Quantum steam tables. Free energy calculations for H2O, D2O, H2S, and H2Se by adaptively optimized Monte Carlo Fourier path integrals

    NASA Astrophysics Data System (ADS)

    Topper, Robert Q.; Zhang, Qi; Liu, Yi-Ping; Truhlar, Donald G.

    1993-03-01

    Converged quantum mechanical vibrational-rotational partition functions and free energies are calculated using realistic potential energy surfaces for several chalcogen dihydrides (H2O, D2O, H2S, H2Se) over a wide range of temperatures (600-4000 K). We employ an adaptively optimized Monte Carlo integration scheme for computing vibrational-rotational partition functions by the Fourier path-integral method. The partition functions and free energies calculated in this way are compared to approximate calculations that assume the separation of vibrational motions from rotational motions. In the approximate calculations, rotations are treated as those of a classical rigid rotator, and vibrations are treated by perturbation theory methods or by the harmonic oscillator model. We find that the perturbation theory treatments yield molecular partition functions which agree closely overall (within ˜7%) with the fully coupled accurate calculations, and these treatments reduce the errors by about a factor of 2 compared to the independent-mode harmonic oscillator model (with errors of ˜16%). These calculations indicate that vibrational anharmonicity and mode-mode coupling effects are significant, but that they may be treated with useful accuracy by perturbation theory for these molecules. The quantal free energies for gaseous water agree well with previously available approximate values for this well studied molecule, and similarly accurate values are also presented for the less well studied D2O, H2S, and H2Se.

  5. Vibrational optical activity in deuteriated phenylethanes

    SciTech Connect

    Abbate, S.; Havel, H.A.; Laux, L.; Pultz, V.; Moscowitz, A.

    1988-06-02

    Infrared, Raman, and vibrational circular dichroism (VCD) spectra have been recorded in the region 3100-2000 cm/sup -1/ for (S)-(+)-1-phenylethane-1-d/sub 1/, (S)-(+)-1-phenylethane-1,2-d/sub 2/, (S)-(+)-1-phenylethane-1,2,2-d/sub 3/, and (S)-(+)-1-phenylethane-1,2,2,2-d/sub 4/. From these spectra the authors have been able to assign fully the aliphatic CD and CH stretching vibrations in all four molecules. Using a harmonic force field which fits the observed frequencies, they have calculated the dipole and rotational strengths of these modes on the basis of the charge flow model. These calculations show that this model underestimates the VCD intensities of these stretching modes. However, the model can be improved through the introduction of polarization terms. Generally applicable analytical expressions for such terms are derived. When applied to the phenylethanes, they lead to the correct orders of magnitude for the rotational strengths.

  6. Using Wave-Packet Interferometry to Monitor the External Vibrational Control of Electronic Excitation Transfer

    E-print Network

    Biggs, Jason D

    2009-01-01

    We investigate the control of electronic energy transfer in molecular dimers through the preparation of specific vibrational coherences prior to electronic excitation, and its observation by nonlinear wave-packet interferometry. Laser-driven coherent nuclear motion can affect the instantaneous resonance between site-excited electronic states and thereby influence short-time electronic excitation transfer (EET). We first illustrate this control mechanism with calculations on a dimer whose constituent monomers undergo harmonic vibrations. We then consider the use of nonlinear wave-packet interferometry (nl-WPI) experiments to monitor the nuclear dynamics accompanying EET in general dimer complexes following impulsive vibrational excitation by a sub-resonant control pulse (or control pulse sequence). In measurements of this kind, two pairs of polarized phase-related femtosecond pulses following the control pulse generate superpositions of coherent nuclear wave packets in optically accessible electronic states. I...

  7. String Vibrations

    NSDL National Science Digital Library

    Davidhazy, Andrew

    This site, by Andrew Davidhazy at the Rochester Institute of Technology, describes how to make interesting and artistic photographs of a vibrating string. Davidhazy explains how the string is vibrated, how the string is lit, and even the exposure time and the effect it has on the resulting image. Four images of the vibrating string are included.

  8. Analysis of potential helicopter vibration reduction concepts

    NASA Technical Reports Server (NTRS)

    Landgrebe, A. J.; Davis, M. W.

    1985-01-01

    Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.

  9. Harmonic generation at high intensities

    SciTech Connect

    Schafer, K.J.; Krause, J.L.; Kulander, K.C.

    1993-06-01

    Atomic electrons subject to intense laser fields can absorb many photons, leading either to multiphoton ionization or the emission of a single, energetic photon which can be a high multiple of the laser frequency. The latter process, high-order harmonic generation, has been observed experimentally using a range of laser wavelengths and intensities over the past several years. Harmonic generation spectra have a generic form: a steep decline for the low order harmonics, followed by a plateau extending to high harmonic order, and finally an abrupt cutoff beyond which no harmonics are discernible. During the plateau the harmonic production is a very weak function of the process order. Harmonic generation is a promising source of coherent, tunable radiation in the XUV to soft X-ray range which could have a variety of scientific and possibly technological applications. Its conversion from an interesting multiphoton phenomenon to a useful laboratory radiation source requires a complete understanding of both its microscopic and macroscopic aspects. We present some recent results on the response of single atoms at intensities relevant to the short pulse experiments. The calculations employ time-dependent methods, which we briefly review in the next section. Following that we discuss the behavior of the harmonics as a function of laser intensity. Two features are notable: the slow scaling of the harmonic intensities with laser intensity, and the rapid variation in the phase of the individual harmonics with respect to harmonic order. We then give a simple empirical formula that predicts the extent of the plateau for a given ionization potential, wavelength and intensity.

  10. First-principle calculation and assignment for vibrational spectra of Ba(Mg{sub 1/3}Nb{sub 2/3})O{sub 3} microwave dielectric ceramic

    SciTech Connect

    Diao, Chuan-Ling [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Wang, Chun-Hai; Lu, Jing [State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Luo, Neng-Neng; Jing, Xi-Ping, E-mail: sf751106@sina.com.cn, E-mail: xpjing@pku.edu.cn [State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Qi, Ze-Ming; Shao, Tao; Wang, Yu-Yin [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Wang, Quan-Chao; Kuang, Xiao-Jun; Fang, Liang [MOE Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004 (China); Shi, Feng, E-mail: sf751106@sina.com.cn, E-mail: xpjing@pku.edu.cn [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China)

    2014-03-21

    1:2 B-site cation ordered Ba(Mg{sub 1/3}Nb{sub 2/3})O{sub 3} ceramic was synthesized using conventional solid-state reaction at 1600?°C for 12?h. The structure parameters were obtained through Rietveld refinement of X-ray diffraction data. The Raman peak frequencies were obtained by Lorenz fitting on Raman spectrum. Four-parameter semiquantum model was used to fit the infrared (IR) reflectivity spectrum, and the fitted parameters were used to calculate the dielectric permittivity ? and dielectric loss tan?. A total of 9 active Raman and 16 active IR modes were obtained using first-principle calculations based on density functional theory with local density approximation. All of the vibrational modes were assigned and represented by linear combinations of the symmetry coordinates deduced using group theory analysis. The Raman mode with the highest frequency A{sub 1g}{sup (4)} (789?cm{sup ?1}) can be described as the breathing vibration of NbO{sub 6}. The IR modes E{sub u}{sup (1)} (149?cm{sup ?1}) and A{sub 2u}{sup (2)} (212?cm{sup ?1}), which can be described as the twisting vibrations of Ba–MgO{sub 6}/Ba–NbO{sub 6} on the a–b plane and the stretching vibrations of Ba–MgO{sub 6}/Ba–NbO{sub 6} along the c direction, respectively, are the dominant contributing modes to ? and tan?. The dielectric property parameters obtained using IR spectrum fittings, first-principal calculations, and microwave measurements were compared.

  11. Adiabatic Invariant of the Harmonic Oscillator

    Microsoft Academic Search

    Russell M. Kulsrud

    1957-01-01

    The problem of a vibrating harmonic oscillator whose frequency is changing in time is considered in the case where the frequency omega is initially constant, varies in an arbitrary fashion and becomes constant again. It is found that the relative change of the quantity, the energy divided by the frequency, in the final region from its value in the initial

  12. Novel zinc(II) and copper(II) complexes of a Mannich base derived from lawsone: Synthesis, single crystal X-ray analysis, ab initio density functional theory calculations and vibrational analysis.

    PubMed

    Neves, Amanda P; Vargas, Maria D; Téllez Soto, Claudio A; Ramos, Joanna M; Visentin, Lorenzo do C; Pinheiro, Carlos B; Mangrich, Antônio S; de Rezende, Edivaltrys I P

    2012-08-01

    Zinc(II) and copper(II) complexes of a tridentate Mannich base L1 derived from 2-hydroxy-1,4-naphthoquinone, pyridinecarboxyaldehyde and 2-aminomethylpyridine, [ZnL1Cl(2)]·H(2)O 1 and [CuL1Cl(2)]·2H(2)O 2, have been synthesized and fully characterized. The structure of complex 1 has been elucidated by a single crystal X-ray diffraction study: the zinc atom is pentacoordinate and the coordination geometry is a distorted square base pyramid, with a geometric structural parameter ? equal to 0.149. Vibrational spectroscopy and ab initio DFT calculations of both compounds have confirmed that the two complexes exhibit similar structures. Full assignment of the vibrational spectra was also supported by careful analysis of the distorted geometries generated by the normal modes. PMID:22513170

  13. Novel zinc(II) and copper(II) complexes of a Mannich base derived from lawsone: Synthesis, single crystal X-ray analysis, ab initio density functional theory calculations and vibrational analysis

    NASA Astrophysics Data System (ADS)

    Neves, Amanda P.; Vargas, Maria D.; Soto, Claudio A. Téllez; Ramos, Joanna M.; Visentin, Lorenzo do C.; Pinheiro, Carlos B.; Mangrich, Antônio S.; de Rezende, Edivaltrys I. P.

    Zinc(II) and copper(II) complexes of a tridentate Mannich base L1 derived from 2-hydroxy-1,4-naphthoquinone, pyridinecarboxyaldehyde and 2-aminomethylpyridine, [ZnL1Cl2]·H2O 1 and [CuL1Cl2]·2H2O 2, have been synthesized and fully characterized. The structure of complex 1 has been elucidated by a single crystal X-ray diffraction study: the zinc atom is pentacoordinate and the coordination geometry is a distorted square base pyramid, with a geometric structural parameter ? equal to 0.149. Vibrational spectroscopy and ab initio DFT calculations of both compounds have confirmed that the two complexes exhibit similar structures. Full assignment of the vibrational spectra was also supported by careful analysis of the distorted geometries generated by the normal modes

  14. Influence of the Vibrational Dissociation Model on the Relaxation of the Excited States Calculated with the CORIA's Collisional-Radiative Model CoRaM-Air

    NASA Astrophysics Data System (ADS)

    Bultel, A.; Annaloro, J.; Schneider, I. F.; Benredjen, D.

    2011-08-01

    In relation with the problem of space vehicles re-entry into the earth atmosphere, we have developed a nonlin- ear electronic and vibrational specific time-dependent Collisional-Radiative (CR) model for air plasma working between 100 Pa and atmospheric pressure and between 2000 K and 20000 K for the translation temperatures. 13 species are considered: N2 , O2 , NO, N, O, Ar, N+ , 2 O+ , NO+ , N+ , O+ , Ar+ and electrons. This model takes 2 into account a total of 335 different states separated in excited electronic states and vibrational states of N2 , O2 and NO on their electronic ground state. Owing to the temperature levels involved, many elementary processes are considered. The CR model is partially validated by comparison with experimental results under atmospheric pressure. Time scales to reach the final steady state are derived. Two models of dissociation are tested with respect to the vibration- translation transfers. The excita- tion and vibrational temperature results are analyzed in a typicalHeaviside-like case at constant pressure and temperature.

  15. Vibrational spectroscopic study of o-, m- and p-hydroxybenzylideneaminoantipyrines

    NASA Astrophysics Data System (ADS)

    Sun, Yu-Xi; Hao, Qing-Li; Lu, Lu-De; Wang, Xin; Yang, Xu-Jie

    2010-01-01

    Three structurally similar antipyrine derivatives of o-hydroxybenzylideneaminoantipyrine ( o-HBAP), m-hydroxybenzylideneaminoantipyrine ( m-HBAP) and p-hydroxybenzylideneaminoantipyrine ( p-HBAP) were characterized by FT-IR, FT-Raman experimental techniques and density functional theoretical (DFT) calculations. The comparisons between the calculated and experimental results covering molecular structures, assignments of fundamental vibrational modes and thermodynamic properties were investigated. The optimized molecular geometries agree well with the corresponding experimental values by comparing with the XRD data. The comparisons and assignments of the vibrational frequencies indicate that the experimental spectra also coincide satisfactorily with those of theoretically simulated spectrograms except the hydrogen-bond coupling infrared vibrations, and compounds can be distinguished by the IR and Raman spectra due to the differences of the hydroxyl-substituted positions and molecular packing, and the strong Raman scattering activities of the compounds are tightly relative to the molecular conjugative moieties linked through the Schiff base imines. The thermodynamic functions and their correlations with temperatures were also obtained from the theoretical harmonic frequencies.

  16. Coupled rotor/airframe vibration analysis

    NASA Technical Reports Server (NTRS)

    Sopher, R.; Studwell, R. E.; Cassarino, S.; Kottapalli, S. B. R.

    1982-01-01

    A coupled rotor/airframe vibration analysis developed as a design tool for predicting helicopter vibrations and a research tool to quantify the effects of structural properties, aerodynamic interactions, and vibration reduction devices on vehicle vibration levels is described. The analysis consists of a base program utilizing an impedance matching technique to represent the coupled rotor/airframe dynamics of the system supported by inputs from several external programs supplying sophisticated rotor and airframe aerodynamic and structural dynamic representation. The theoretical background, computer program capabilities and limited correlation results are presented in this report. Correlation results using scale model wind tunnel results show that the analysis can adequately predict trends of vibration variations with airspeed and higher harmonic control effects. Predictions of absolute values of vibration levels were found to be very sensitive to modal characteristics and results were not representative of measured values.

  17. Vibrational spectroscopic studies and Natural Bond Orbital analysis of 4,6-dichloro-2-(methylthio)pyrimidine based on density functional theory

    Microsoft Academic Search

    V. Balachandran; A. Lakshmi; A. Janaki

    2011-01-01

    The FT-IR and FT-Raman spectra of 4,6-dichloro-2-(methylthio)pyrimidine (DMP) have been recorded and analyzed. The optimized geometry, intramolecular hydrogen bonding, and harmonic vibrational wave numbers of DMP have been investigated with the help of B3LYP density functional theory (DFT) method supplemented with 6-31G** basis set. The infrared and Raman spectra were predicted theoretically from the calculated intensities. Natural Bond Orbital (NBO)

  18. Force distortion in resonance testing of structures with electro-dynamic vibration exciters

    Microsoft Academic Search

    G. R. Tomlinson

    1979-01-01

    Distortion of the harmonic input force delivered by an electrodynamic vibration exciter in the resonance testing of structures is investigated. It is shown that the distortion is primarily second harmonic and due to nonlinearities in the magnetic field of the exciter. It is found that damping in the structure under test significantly greater than the vibration exciter to test structure

  19. Vibrational C-H overtone spectroscopy and bond distances of butenes dissolved in liquid Xe

    NASA Astrophysics Data System (ADS)

    Lopez-Calvo, Alfredo; Diez-y-Riega, Helena; Manzanares, Carlos E.

    2009-10-01

    Vibrational overtone spectra of isobutene, cis-2-butene, and trans-2-butene dissolved in liquid xenon at 163 K, have been recorded between 5000 and 16500 cm -1. Spectral regions for the first four overtones were measured using a Fourier transform spectrophotometer. The fifth overtone (? ? = 6) spectra were recorded with a double beam (pump-probe) thermal lens technique. Band deconvolution allowed isolation of individual transitions. Local-mode parameters were calculated for C-H oscillators in solution and compared with gas phase local-mode parameters. Density functional theory calculations were done to obtain C-H bond lengths and vibrational frequencies for the three butene isomers. Frequency shifts (? ?) with respect to gas phase results are attributed to changes in harmonic frequency and anharmonicity of the particular C-H bond of the sample dissolved in the inert liquid solvent.

  20. spherical harmonics for l

    DOE PAGESBeta

    Michael, J. Robert; Volkov, Anatoliy

    2015-01-23

    The widely used pseudoatom formalism [Stewart (1976). Acta Cryst. A32, 565–574; Hansen & Coppens (1978). Acta Cryst. A34, 909–921] in experimental X-ray charge-density studies makes use of real spherical harmonics when describing the angular component of aspherical deformations of the atomic electron density in molecules and crystals. The analytical form of the densitynormalized Cartesian spherical harmonic functions for up to l 7 and the corresponding normalization coefficients were reported previously by Paturle & Coppens [Acta Cryst. (1988), A44, 6–7]. It was shown that the analytical form for normalization coefficients is available primarily for l 4 [Hansen & Coppens, 1978; Paturlemore »& Coppens, 1988; Coppens (1992). International Tables for Crystallography, Vol. B, Reciprocal space, 1st ed., edited by U. Shmueli, ch. 1.2. Dordrecht: Kluwer Academic Publishers; Coppens (1997). X-ray Charge Densities and Chemical Bonding. New York: Oxford University Press]. Only in very special cases it is possible to derive an analytical representation of the normalization coefficients for 4 4 the density normalization coefficients were calculated numerically to within seven significant figures. In this study we review the literature on the density-normalized spherical harmonics, clarify the existing notations, use the Paturle–Coppens (Paturle & Coppens, 1988) method in the Wolfram Mathematica software to derive the Cartesian spherical harmonics for l 20 and determine the density normalization coefficients to 35 significant figures, and computer-generate a Fortran90 code. The article primarily targets researchers who work in the field of experimental X-ray electron density, but may be of some use to all who are interested in Cartesian spherical harmonics.« less

  1. Vibrational and rotational excitation of CO in comets. Part 1: Non-equilibrium calculations. Part 2: Results of the calculation for standard bright comet, comet Iras-Araki-Alcock and comet Halley

    NASA Technical Reports Server (NTRS)

    Chin, G.; Weaver, H. A.

    1984-01-01

    The vibrational and rotational excitation of the CO molecule in cometary comae were investigated using a model which includes IR vibrational pumping by the solar flux, vibrational and rotational radiative decay, and collisional coupling among rotational states. Steady state was not assumed in solving the rate equations. The evolution of a shell of CO gas was monitored as it expanded from the nucleus into the outer coma. Collisional effects were treated using a kinetic temperature profile derived from theoretical work on the coma energy balance. The kinetic temperature was assumed to be extremely cold in the inner coma; this has significant consequences for the CO excitation. If optical depth effects are ignored, only low J transitions will be significantly excited in comets observed at high spatial resolution. Ground-based observations of CO co-vibrational and rotational transitions will be extremely difficult due to lack of sensitivity and/or terrestrial absorption. However, CO should be detectable from a large comet with favorable observing geometry if the CO is a parent molecule present at the 10% level (or greater) relative to H2O. Observations using cooled, spaceborne instruments should be capable of detecting CO emission from even moderately bright comets.

  2. The effects of static quartic anharmonicity on the quantum dynamics of a linear oscillator with time-dependent harmonic frequency: Perturbative analysis and numerical calculations

    SciTech Connect

    Sarkar, P.; Bhattacharyya, S.P. [Indian Association for the Cultivation of Science, Calcutta (India)

    1995-06-15

    The effects of quartic anharmonicity on the quantum dynamics of a linear oscillator with time-dependent force constant (K) or harmonic frequency ({omega}) are studied both perturbatively and numerically by the time-dependent Fourier grid Hamiltonian method. In the absence of anharmonicity, the ground-state population decreases and the population of an accessible excited state (k = 2.4, 6 ... ) increases with time. However, when anharmonicity is introduced, both the ground- and excited-state populations show typical oscillations. For weak coupling, the population of an accessible excited state at a certain instant of time (short) turns out to be a parabolic function of the anharmonic coupling constant ({lambda}), when all other parameters of the system are kept fixed. This parabolic nature of the excited-state population vs. the {lambda} profile is independent of the specific form of the time dependence of the force constant, K{sub t}. However, it depends upon the rate at which K{sub t} relaxes. For small anharmonic coupling strength and short time scales, the numerical results corroborate expectations based on the first-order time-dependent perturbative analysis, using a suitably repartitioned Hamiltonian that makes H{sub 0} time-independent. Some of the possible experimental implications of our observations are analyzed, especially in relation to intensity oscillations observed in some charge-transfer spectra in systems in which the dephasing rates are comparable with the time scale of the electron transfer. 21 refs., 7 figs., 1 tab.

  3. Monitoring Bearing Vibrations For Signs Of Damage

    NASA Technical Reports Server (NTRS)

    Martinez, Carol L.

    1991-01-01

    Real-time spectral analysis of vibrations being developed for use in monitoring conditions of critical bearings in rotating machinery. Underlying concept simple and fairly well established: appearance and growth of vibrations at frequencies associated with rotations of various parts of bearing system indicate wear, damage, and imperfections of manufacture. Frequencies include fundamental and harmonics of frequency of rotation of ball cage, frequency of passage of balls, and frequency of rotation of shaft.

  4. PREFACE: Vibrations at surfaces Vibrations at surfaces

    NASA Astrophysics Data System (ADS)

    Rahman, Talat S.

    2011-12-01

    This special issue is dedicated to the phenomenon of vibrations at surfaces—a topic that was indispensible a couple of decades ago, since it was one of the few phenomena capable of revealing the nature of binding at solid surfaces. For clean surfaces, the frequencies of modes with characteristic displacement patterns revealed how surface geometry, as well as the nature of binding between atoms in the surface layers, could be different from that in the bulk solid. Dispersion of the surface phonons provided further measures of interatomic interactions. For chemisorbed molecules on surfaces, frequencies and dispersion of the vibrational modes were also critical for determining adsorption sites. In other words, vibrations at surfaces served as a reliable means of extracting information about surface structure, chemisorption and overlayer formation. Experimental techniques, such as electron energy loss spectroscopy and helium-atom-surface scattering, coupled with infra-red spectroscopy, were continually refined and their resolutions enhanced to capture subtleties in the dynamics of atoms and molecules at surfaces. Theoretical methods, whether based on empirical and semi-empirical interatomic potential or on ab initio electronic structure calculations, helped decipher experimental observations and provide deeper insights into the nature of the bond between atoms and molecules in regions of reduced symmetry, as encountered on solid surfaces. Vibrations at surfaces were thus an integral part of the set of phenomena that characterized surface science. Dedicated workshops and conferences were held to explore the variety of interesting and puzzling features revealed in experimental and theoretical investigations of surface vibrational modes and their dispersion. One such conference, Vibrations at Surfaces, first organized by Harald Ibach in Juelich in 1980, continues to this day. The 13th International Conference on Vibrations at Surfaces was held at the University of Central Florida, Orlando, in March 2010. Several speakers at this meeting were invited to contribute to the special section in this issue. As is clear from the articles in this special section, the phenomenon of vibrations at surfaces continues to be a dynamic field of investigation. In fact, there is a resurgence of effort because the insights provided by surface dynamics are still fundamental to the development of an understanding of the microscopic factors that control surface structure formation, diffusion, reaction and structural stability. Examination of dynamics at surfaces thus complements and supplements the wealth of information that is obtained from real-space techniques such as scanning tunneling microscopy. Vibrational dynamics is, of course, not limited to surfaces. Surfaces are important since they provide immediate deviation from the bulk. They display how lack of symmetry can lead to new structures, new local atomic environments and new types of dynamical modes. Nanoparticles, large molecules and nanostructures of all types, in all kinds of local environments, provide further examples of regions of reduced symmetry and coordination, and hence display characteristic vibrational modes. Given the tremendous advance in the synthesis of a variety of nanostructures whose functionalization would pave the way for nanotechnology, there is even greater need to engage in experimental and theoretical techniques that help extract their vibrational dynamics. Such knowledge would enable a more complete understanding and characterization of these nanoscale systems than would otherwise be the case. The papers presented here provide excellent examples of the kind of information that is revealed by vibrations at surfaces. Vibrations at surface contents Poisoning and non-poisoning oxygen on Cu(410)L Vattuone, V Venugopal, T Kravchuk, M Smerieri, L Savio and M Rocca Modifying protein adsorption by layers of glutathione pre-adsorbed on Au(111)Anne Vallée, Vincent Humblot, Christophe Méthivier, Paul Dumas and Claire-Marie Pradier Relating temperature dependence of atom

  5. Experimental and DFT studies on the vibrational and electronic spectra of 2-(4,5-phenyl-1H-imidazole-2-yl)-phenol

    NASA Astrophysics Data System (ADS)

    Ye, Yunfeng; Tang, Guodong; Tang, Tingting; Culnane, Lance F.; Zhao, Jianyin; Zhang, Yu

    2015-02-01

    The compound 2-(4,5-phenyl-1H-imidazole-2-yl-phenol (PIP) was synthesized, followed by structure determination by X-ray diffraction, the results of which agree well with the calculated optimized, lowest energy geometrical structure. Vibrational information was obtained by FT-IR and Raman spectroscopy which also agree well with calculations (of harmonic vibration frequencies). The calculations were carried out with density functional theory B3LYP methods using 6-311++G** and LANL2DZ basis sets. Absorption UV-Vis experiments of PIP in CH3CH2OH solution reveal three maximum peaks at 245, 292 and 317 nm, which are in agreement with calculated electronic transitions using TD-B3LYP/6-311++G** in CH3CH2OH solution, and agree to the gas-phase calculations.

  6. Vibrational, UV spectra, NBO, first order hyperpolarizability and HOMO-LUMO analysis of carvedilol

    NASA Astrophysics Data System (ADS)

    Swarnalatha, N.; Gunasekaran, S.; Nagarajan, M.; Srinivasan, S.; Sankari, G.; Ramkumaar, G. R.

    2015-02-01

    In this work, we have investigated experimentally and theoretically on the molecular structure, vibrational spectra, UV spectral analysis and NBO studies of cardio-protective drug carvedilol. The FT-Raman and FT-IR spectra for carvedilol in the solid phase have been recorded in the region 4000-100 cm-1 and 4000-400 cm-1 respectively. Theoretical calculations were performed by using density functional theory (DFT) method at B3LYP/6-31G(d,p) and B3LYP/6-31++G(d,p) basis set levels. The harmonic vibrational frequencies, the optimized geometric parameters have been interpreted and compared with the reported experimental values. The complete vibrational assignments were performed on the basis of potential energy distribution (PED) of the vibrational modes. The thermodynamic properties and molecular electrostatic potential surfaces of the molecule were constructed. The electronic absorption spectrum was recorded in the region 400-200 nm and electronic properties such as HOMO and LUMO energies were calculated. The stability of the molecule arising from hyper conjugative interactions and charge delocalization have been analyzed from natural bond orbital (NBO) analysis. The first order hyperpolarizability of the title molecule was also calculated. The photo stability of carvedilol under different storage conditions were analyzed using UV-Vis spectral technique.

  7. Vibration isolation

    NASA Technical Reports Server (NTRS)

    Bastin, Paul

    1990-01-01

    Viewgraphs on vibration isolation are presented. Techniques to control and isolate centrifuge disturbances were identified. Topics covered include: disturbance sources in the microgravity environment; microgravity assessment criteria; life sciences centrifuge; flight support equipment for launch; active vibration isolation system; active balancing system; and fuzzy logic control.

  8. Good Vibrations

    NSDL National Science Digital Library

    OMSI

    2004-01-01

    In this activity, learners experiment with their voices and noisemakers to understand the connections between vibrations and the sounds created by those vibrations. This resource includes three quick demonstration activities that can be used independently or as a group to introduce learners to the basic elements of sound.

  9. Complex Energy of Harmonic Oscillator under Non-Hermitian transformation of momentum with real wave function

    E-print Network

    Biswanath Rath

    2015-05-19

    For the first time in the literature of Quantum Physics, we present complex energy eigenvalues of non-Hermitian Harmonic Oscillator $H=\\frac{(p+iLx)}^{2}}{2} + W^{2} \\frac{x^{2}}{2}$ with real wave function having positive frequency of vibration $(w)$ under some selective choice of $L$ and $W$ .Interestingly for the same values of $L$ and $W$, if the frequency of vibration $w$ in the real wave function is (some how) related as $w=L\\pmW$ or $w=W-L$ then the same oscillator can reflect either pure positive or negative energy eigenvalues.The real energy levels are in conformity with the perturbative calculation. PACS :03.65.Db;11.39.Er. Key words: Positive frequency, real wave function, complex energy, real positive energy,negative energy.

  10. Influence of vibration amplitude on laminar flow over a plate vibrating at low Strouhal number

    SciTech Connect

    Venkat, N.K. (Spaulding Environmental Associates, Inc., Wakefield, RI (United States)); Spaulding, M. (Univ. of Rhode Island, Kingston, RI (United States). Dept. of Ocean Engineering)

    1993-09-01

    The spectral and hydrodynamic response of laminar flow over a flat plate with a vibrating section forced in sinusoidal motion with a dimensionless amplitude ratio, H[sub 0] (vibration amplitude divided by plate length) varying in the range 0.0 < H[sub 0] < 0.1 is analyzed using numerical simulations. The Reynolds number, Re, based on the length of the vibrating plate, is fixed at 1,000. The flow is simulated for Strouhal number, St, = 0.25 (low frequency). The spectral characteristics are obtained by performing Fast Fourier Transform (FFT) on the pressure coefficient time series data. The hydrodynamic analysis is performed by plotting stream function contour plot in the vicinity of the vibrating section for one vibration cycle. The model predicted results show that the friction and pressure coefficients over the vibrating body vary with vibration amplitude. For low amplitude ratios, the interaction of the external flow with the vibrating section is linear and there is little up or downstream influence. For high H[sub 0], there is considerable downstream influence of the disturbance. Nonlinear energy transfer, as evidenced by the existence of a significant first harmonic in the pressure wave, takes place between the vibrating plate and the flow field. Energy transfer to the higher harmonics is less significant.

  11. Molecular structure, vibrational spectra, NLO and NBO analysis of bis(8-oxy-1-methylquinolinium) hydroiodide

    NASA Astrophysics Data System (ADS)

    Pir, H.; Günay, N.; Avc?, D.; Atalay, Y.

    2012-10-01

    In this paper, quantum chemistry calculations of geometric parameters, harmonic vibrational wavenumbers, molecular frontier orbital energies (HOMO and LUMO) and the electronic properties of bis(8-oxy-1-methylquinolinium) hydroiodide ([(C10H9NO)2H+]·I-) have been performed by using Gaussian 09 program. The structural and spectroscopic data of the molecule in the ground state have been calculated by using Hartree-Fock (HF) and density functional method (DFT/B3LYP) with the LanL2DZ basis set. For the spectra predicted, a potential energy distribution (PED) is calculated. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts values of bis(8-oxy-1-methylquinolinium) hydroiodide molecule have been calculated by the gage including atomic orbital (GIAO) method. Furthermore, molecular electrostatic potential maps (MEP), Mulliken charges and the natural bonding orbital (NBO) analysis of the compound have been calculated by the HF and B3LYP/Lanl2DZ methods.

  12. Resonant-Convergent PCM Response Theory for the Calculation of Second Harmonic Generation in Makaluvamines A-V: Pyrroloiminoquinone Marine Natural Products from Poriferans of Genus Zyzzya.

    PubMed

    Milne, Bruce F; Norman, Patrick

    2015-05-28

    The first-order hyperpolarizability, ?, has been calculated for a group of marine natural products, the makaluvamines. These compounds possess a common cationic pyrroloiminoquinone structure that is substituted to varying degrees. Calculations at the MP2 level indicate that makaluvamines possessing phenolic side chains conjugated with the pyrroloiminoquinone moiety display large ? values, while breaking this conjugation leads to a dramatic decrease in the calculated hyperpolarizability. This is consistent with a charge-transfer donor-?-acceptor (D-?-A) structure type, characteristic of nonlinear optical chromophores. Dynamic hyperpolarizabilities calculated using resonance-convergent time-dependent density functional theory coupled to polarizable continuum model (PCM) solvation suggest that significant resonance enhancement effects can be expected for incident radiation with wavelengths around 800 nm. The results of the current work suggest that the pyrroloiminoquinone moiety represents a potentially useful new chromophore subunit, in particular for the development of molecular probes for biological imaging. The introduction of solvent-solute interactions in the theory is conventionally made in a density matrix formalism, and the present work will provide detailed account of the approximations that need to be introduced in wave function theory and our program implementation. The program implementation as such is achieved by a mere combination of existing modules from previous developments, and it is here only briefly reviewed. PMID:25584854

  13. Vertical vibration and shape oscillation of acoustically levitated water drops

    NASA Astrophysics Data System (ADS)

    Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B.

    2014-09-01

    We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

  14. Current-based sensorless vibration monitoring of small synchronous machines

    Microsoft Academic Search

    C. M. Riley; T. G. Habetler

    1998-01-01

    This paper presents an initial study into the relationship between mechanical vibrations and their effect on the airgap and the resultant stator and field current harmonics in low and medium voltage synchronous machines. Experimental results show that the modulation of the airgap by mechanical vibrations can be detected in the stator and field current spectra and are monotonically related for

  15. Vibrational relaxation and vibrational cooling in low temperature molecular crystals

    NASA Astrophysics Data System (ADS)

    Hill, Jeffrey R.; Chronister, Eric L.; Chang, Ta-Chau; Kim, Hackjin; Postlewaite, Jay C.; Dlott, Dana D.

    1988-01-01

    The processes of vibrational relaxation (VR) and vibrational cooling (VC) are investigated in low temperature crystals of complex molecules, specifically benzene, naphthalene, anthracene, and durene. In the VR process, a vibration is deexcited, while VC consists of many sequential and parallel VR steps which return the crystal to thermal equilibrium. A theoretical model is developed which relates the VR rate to the excess vibrational energy, the molecular structure, and the crystal structure. Specific relations are derived for the vibrational lifetime T1 in each of three regimes of excess vibrational energy. The regimes are the following: Low frequency regime I where VR occurs by emission of two phonons, intermediate frequency regime II where VR occurs by emission of one phonon and one vibration, and high frequency regime III where VR occurs by evolution into a dense bath of vibrational combinations. The VR rate in each regime depends on a particular multiphonon density of states and a few averaged anharmonic coefficients. The appropriate densities of states are calculated from spectroscopic data, and together with available VR data and new infrared and ps Raman data, the values of the anharmonic coefficients are determined for each material. The relationship between these parameters and the material properties is discussed. We then describe VC in a master equation formalism. The transition rate matrix for naphthalene is found using the empirically determined parameters of the above model, and the time dependent redistribution in each mode is calculated.

  16. Harmonic engine

    DOEpatents

    Bennett, Charles L.; Sewall, Noel; Boroa, Carl

    2014-08-19

    An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into of the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. Upon releasing the inlet valve the inlet valve head undergoes a single oscillation past the equilibrium positio to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. Protrusions carried either by the inlet valve head or piston head are used to bump open the inlet valve from the closed position and initiate the single oscillation of the inlet valve head, and protrusions carried either by the outlet valve head or piston head are used to close the outlet valve ahead of the bump opening of the inlet valve.

  17. A computer program to calculate zeroes, extrema, and interval integrals for the associated Legendre functions. [for estimation of bounds of truncation error in spherical harmonic expansion of geopotential

    NASA Technical Reports Server (NTRS)

    Payne, M. H.

    1973-01-01

    A computer program is described for the calculation of the zeroes of the associated Legendre functions, Pnm, and their derivatives, for the calculation of the extrema of Pnm and also the integral between pairs of successive zeroes. The program has been run for all n,m from (0,0) to (20,20) and selected cases beyond that for n up to 40. Up to (20,20), the program (written in double precision) retains nearly full accuracy, and indications are that up to (40,40) there is still sufficient precision (4-5 decimal digits for a 54-bit mantissa) for estimation of various bounds and errors involved in geopotential modelling, the purpose for which the program was written.

  18. Nonlinear cyclotron harmonic absorption

    SciTech Connect

    Seol, Jae Chun [National Fusion Research Institute, Yuseong, Daejeon 555-333 (Korea, Republic of); Hegna, C. C.; Callen, J. D. [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706-1609 (United States)

    2009-05-15

    Nonlinear oscillations of particle's energy occur when a particle stays in a resonance zone. In this work, we found that collisionless heating of particles occurs when they pass the microwave beam at first, second, and third harmonic resonances. It is found that the net energy gain of particles from the microwaves is inversely proportional to the wave frequency. It is also found that the net energy gain is dependent on the microwave beam width. The energy gain of particles from a single pass through a resonance zone has been formulated analytically. A numerical calculation has been performed and the results are in good agreement with the analytic calculation. Both analytic and numerical calculations show a strong frequency dependence and a beam width dependence of nonlinear cyclotron resonance heating.

  19. A Vibration-Based Condition Monitoring System for Switched Reluctance Machine Rotor Eccentricity Detection

    Microsoft Academic Search

    D. G. Dorrell; C. Cossar

    2008-01-01

    We propose a condition monitoring strategy for the detection of rotor eccentricity in switched reluctance machines. It uses vibration measurements and harmonic analysis to generate a Fourier series for the vibrations. Assessment of the change in key vibration components allows development of an eccentricity index that can give an indication of increasing eccentricity. The method discriminates between static and dynamic

  20. Adelic Harmonic Oscillator

    E-print Network

    Branko Dragovich

    2004-04-21

    Using the Weyl quantization we formulate one-dimensional adelic quantum mechanics, which unifies and treats ordinary and $p$-adic quantum mechanics on an equal footing. As an illustration the corresponding harmonic oscillator is considered. It is a simple, exact and instructive adelic model. Eigenstates are Schwartz-Bruhat functions. The Mellin transform of a simplest vacuum state leads to the well known functional relation for the Riemann zeta function. Some expectation values are calculated. The existence of adelic matter at very high energies is suggested.

  1. Analysis of Vibration and Acoustic Noise in Permanent Magnet Motors.

    NASA Astrophysics Data System (ADS)

    Hwang, Sangmoon

    The drive motor is a frequent source of vibration and acoustic noise in many precision spindle motors. One of the electromagnetic sources of vibration in permanent magnet motors is the torque ripple, consisting of the reluctance torque and electromagnetic torque fluctuation. This type of vibration is becoming more serious with the advent of new high-grade magnets with increased flux density. Acoustic noise of electromagnetic origin is difficult to predict and its exact mechanism is unclear. The mechanism of noise generation should be revealed to design a quieter motor which is the modern customer's demand. For motor operation at low speeds and loads, torque ripple due to the reluctance torque is often a source of vibration and control difficulty. The reluctance torque in a motor was calculated from the flux density by a finite element method and the Maxwell stress method. Effects of design parameters, such as stator slot width, permanent slot width, airgap length and magnetization direction, were investigated. Magnet pole shaping, by gradually decreasing the magnet thickness toward edges, yields a sinusoidal shape of the reluctance torque with reduced harmonics, thus reducing the vibration. This dissertation also presents two motor design techniques: stator tooth notching and rotor pole skewing with magnet pole shaping, and the effect of each method on the output torque. The analysis shows that the reluctance torque can be nearly eliminated by the suggested designs, with minimal sacrifice of the output torque. In permanent magnet DC motors, the most popular design type is the trapezoidal back electro-motive force (BEMF), for switched DC controllers. It is demonstrated that the output torque profile of one phase energized is qualitatively equivalent to the BEMF profile for motors with reduced reluctance torque. It implies that design of BEMF profile is possible by magnetic modeling of a motor, without expensive and time-consuming experiments for different designs. The effect of various design parameters on the output torque and torque ripple are discussed. Design parameters include winding patterns, magnetization direction, magnet arc length, number of segments in poles and magnet pole shaping. New designs of trapezoidal BEMF motors are proposed to reduce the electromagnetic torque ripple. Magnet stepping and magnet edge shaping with reduced arc length, significantly reduce torque ripple, with minimal sacrifice of the maximum output torque. Acoustic noise of electromagnetic origin is investigated using a magnetic frame which emulates a DC motor. The driving electromagnetic force is calculated using finite element analysis and the resulting vibration and acoustic noise is measured. Acoustic noise of purely electromagnetic origin was also tested with a DC brushless motor to confirm the results of the magnetic frame. The mechanism of noise generation in a DC motor is a quasi-static response of a stator not only at the fundamental frequency but also at higher harmonic frequencies of alternating switched DC, which is a current characteristic of a DC motor. Noise generation is significantly aggravated when some of those harmonics are close to the resonant frequencies of the stator. Therefore, acoustic noise is highly dependent upon the excitation current shape, as higher harmonics may match with resonant frequencies of the stator.

  2. Analysis of Transverse Vibration of Antenna Structure Resonator Using Bernoulli-Euler Beam Theory and Quantum Mechanical Examination of Its Quantized Displacement

    NASA Astrophysics Data System (ADS)

    Itoh, Hideaki; Ishikawa, Kiyoshi; Kobayashi, Yoshitada

    2008-07-01

    We analytically investigated the vibration of a macroscopic antenna structure resonator of 10.7 µm length showing a quantized displacement at 110 mK using Bernoulli-Euler beam theory. According to our calculations on the vibrational displacement and mode of the resonator, the vibration mode increased step-by-step from the 1st to 10th mode and then repeated again from the 1st to 10th mode. We found the 10th mode of the resonator at 1.592 GHz when using every paddle length of 490 nm, which is 10 nm shorter than that of a usual antenna structure resonator, existed near a frequency of 1.49 GHz at which the quantized displacement was observed. In the 10th mode of the antenna structure resonator at 1.592 GHz, the displacement of the central beam was so extensively damped that its mechanical energy may be considered to be zero. Therefore, the mechanical energy of the antenna structure resonator could be approximately calculated from the displacement of forty paddles regarded as cantilever beams. We could explain the quantized displacement of the antenna structure resonator using the equivalent mass of a harmonic oscillator, to which the antenna structure resonator was approximately equivalent in mechanical energy, and the quantization of a harmonic oscillator in a textbook on quantum mechanics if the wave function of quantum mechanics can be applied to this harmonic oscillator.

  3. Piezoelectric energy harvesting from broadband random vibrations

    Microsoft Academic Search

    S. Adhikari; M. I. Friswell; D. J. Inman

    2009-01-01

    Energy harvesting for the purpose of powering low power electronic sensor systems has received explosive attention in the last few years. Most works using deterministic approaches focusing on using the piezoelectric effect to harvest ambient vibration energy have concentrated on cantilever beams at resonance using harmonic excitation. Here, using a stochastic approach, we focus on using a stack configuration and

  4. Vibration sensors

    NASA Astrophysics Data System (ADS)

    Gupta, Amita; Singh, Ranvir; Ahmad, Amir; Kumar, Mahesh

    2003-10-01

    Today, vibration sensors with low and medium sensitivities are in great demand. Their applications include robotics, navigation, machine vibration monitoring, isolation of precision equipment & activation of safety systems e.g. airbags in automobiles. Vibration sensors have been developed at SSPL, using silicon micromachining to sense vibrations in a system in the 30 - 200 Hz frequency band. The sensing element in the silicon vibration sensor is a seismic mass suspended by thin silicon hinges mounted on a metallized glass plate forming a parallel plate capacitor. The movement of the seismic mass along the vertical axis is monitored to sense vibrations. This is obtained by measuring the change in capacitance. The movable plate of the parallel plate capacitor is formed by a block connected to a surrounding frame by four cantilever beams located on sides or corners of the seismic mass. This element is fabricated by silicon micromachining. Several sensors in the chip sizes 1.6 cm x 1.6 cm, 1 cm x 1 cm and 0.7 cm x 0.7 cm have been fabricated. Work done on these sensors, techniques used in processing and silicon to glass bonding are presented in the paper. Performance evaluation of these sensors is also discussed.

  5. Vibration disease.

    PubMed

    Kákosy, T

    1989-04-01

    Today, in this age of technology, vibration caused by machinery is an almost universal hazard. Vibration transferred from a machine to the human body may cause discomfort, a reduction of performance, and even injury. Vibratory manual tools may cause damage to the circulatory system of the upper extremities (Raynaud's syndrome), to the peripheral nerves (peripheral neuropathy), and to the bones and joints (aseptic necrosis, fatigue fractures, degenerative joint disease). Vehicles and machines causing floor vibration cause degenerative disc disease of the lumbar spine. The pathogenesis of vibration injuries is still not completely clear and there is no effective treatment. Some of the abnormalities are irreversible and may cause permanent decrease of working ability, and even unemployment. This is why prevention is so important. Prevention is complex, including technical and organizational measures, use of individual protective clothing and footwear, and medical supervision both before and during employment. Workers who are exposed to vibration should be protected against other aggravating factors such as cold and noise, etc. Vibration-induced injuries are recognized in law in many countries as grounds for financial compensation. Their cost to industry is rising and, unless a means of prevention or cure is found, will continue to do so in the foreseeable future. PMID:2661029

  6. First principles study on the molecular structure and vibrational spectra of ketoprofen

    NASA Astrophysics Data System (ADS)

    Liu, Lekun; Gao, Hongwei

    2012-11-01

    The aim of this work was to compare the performance of different DFT methods at different basis sets in predicting geometry and vibration spectrum of ketoprofen. The molecular geometry and vibrational frequencies of ketoprofen have been calculated using five different density function theory (DFT) methods, including LSDA, B3LYP, mPW1PW91, B3PW91 and HCTH, with various basis sets, including 6-311G, 6-311+G, 6-311++G, 6-311+G (d, p) and 6-311++G (2d, 2p). The results indicate that mPW1PW91/6-311++G (2d, 2p) level is clearly superior to all the remaining density functional methods in predicting the bond lengths and bond angles of ketoprofen. Mean absolute deviations between the calculated harmonic and observed fundamental vibration frequencies for each method shows that LSDA/6-311G method is the best to predict vibrational spectra of ketoprofen comparing other DFT methods.

  7. Vibrational Energies of the CO2 Molecule

    Microsoft Academic Search

    V. Robert Stull; Philip J. Wyatt; Gilbert N. Plass

    1962-01-01

    The vibrational energy levels of the eight most abundant isotopic species of carbon dioxide have been calculated. Over 1800 energy levels are given for each isotope. The calculations included terms to the third order in the vibrational quantum numbers and took account of the Fermi resonance. The matrices were diagonalized by an eigenvalue routine of great accuracy.

  8. Dynamics of the [4Fe-4S] Cluster in Pyrococcus furiosus D14C Ferredoxin via Nuclear Resonance Vibrational and Resonance Raman Spectroscopies, Force Field Simulations, and Density Functional Theory Calculations

    PubMed Central

    Mitra, Devrani; Pelmenschikov, Vladimir; Guo, Yisong; Case, David A.; Wang, Hongxin; Dong, Weibing; Tan, Ming-Liang; Ichiye, Toshiko; Jenney, Francis E.; Adams, Michael W. W.; Yoda, Yoshitaka; Zhao, Jiyong; Cramer, Stephen P.

    2011-01-01

    We have used 57Fe nuclear resonance vibrational spectroscopy (NRVS) to study oxidized and reduced forms of the [4Fe-4S] cluster in the D14C variant ferredoxin from Pyrococcus furiosus (Pf D14C Fd). To assist the normal mode assignments, we recorded the NRVS of D14C ferredoxin samples with 36S substituted into the [4Fe-4S] cluster bridging sulfide positions, and a model compound without ligand side chains: (Ph4P)2[Fe4S4Cl4]. Several distinct regions of NRVS intensity are identified, ranging from `protein' and torsional modes below 100 cm?1, through bending and breathing modes near 150 cm?1, to strong bands from Fe-S stretching modes between 250 cm?1 and ~400 cm?1. The oxidized ferredoxin samples were also investigated by resonance Raman (RR) spectroscopy. We found good agreement between NRVS and RR frequencies, but because of different selection rules, the intensities vary dramatically between the two types of spectra. The 57Fe partial vibrational densities of states (PVDOS) for the oxidized samples were interpreted by normal mode analysis with optimization of Urey-Bradley force fields for local models of the [4Fe-4S] clusters. Full protein model calculations were also conducted using a supplemented CHARMM force field, and these calculations revealed low frequency modes that may be relevant to electron transfer with Pf Fd partners. Density functional theory (DFT) calculations complemented these empirical analyses, and DFT was used to estimate the reorganization energy associated with the [Fe4S4]2+/1+ redox cycle. Overall, the NRVS technique demonstrates great promise for the observation and quantitative interpretation of the dynamical properties of Fe-S proteins. PMID:21500788

  9. Structural, vibrational and thermodynamic properties of Mg2 FeH6 complex hydride

    NASA Astrophysics Data System (ADS)

    Zhou, H. L.; Yu, Y.; Zhang, H. F.; Gao, T.

    2011-02-01

    Mg2FeH6, which has one of the highest hydrogen storage capacities among Mg based 3d-transitional metal hydrides, is considered as an attractive material for hydrogen storage. Within density-functional perturbation theory (DFPT), we have investigated the structural, vibrational and thermodynamic properties of Mg2FeH6. The band structure calculation shows that this compound is a semiconductor with a direct X-X energy gap of 1.96 eV. The calculated phonon frequencies for the Raman-active and the infrared-active modes are assigned. The phonon dispersion curves together with the corresponding phonon density of states and longitudinal-transverse optical (LO-TO) splitting are also calculated. Findings are also presented for the temperature-dependent behaviors of some thermodynamic properties such as free energy, internal energy, entropy and heat capacity within the quasi-harmonic approximation based on the calculated phonon density of states.

  10. Random Vibrations

    NASA Technical Reports Server (NTRS)

    Messaro. Semma; Harrison, Phillip

    2010-01-01

    Ares I Zonal Random vibration environments due to acoustic impingement and combustion processes are develop for liftoff, ascent and reentry. Random Vibration test criteria for Ares I Upper Stage pyrotechnic components are developed by enveloping the applicable zonal environments where each component is located. Random vibration tests will be conducted to assure that these components will survive and function appropriately after exposure to the expected vibration environments. Methodology: Random Vibration test criteria for Ares I Upper Stage pyrotechnic components were desired that would envelope all the applicable environments where each component was located. Applicable Ares I Vehicle drawings and design information needed to be assessed to determine the location(s) for each component on the Ares I Upper Stage. Design and test criteria needed to be developed by plotting and enveloping the applicable environments using Microsoft Excel Spreadsheet Software and documenting them in a report Using Microsoft Word Processing Software. Conclusion: Random vibration liftoff, ascent, and green run design & test criteria for the Upper Stage Pyrotechnic Components were developed by using Microsoft Excel to envelope zonal environments applicable to each component. Results were transferred from Excel into a report using Microsoft Word. After the report is reviewed and edited by my mentor it will be submitted for publication as an attachment to a memorandum. Pyrotechnic component designers will extract criteria from my report for incorporation into the design and test specifications for components. Eventually the hardware will be tested to the environments I developed to assure that the components will survive and function appropriately after exposure to the expected vibration environments.

  11. New marine harmonic standards

    Microsoft Academic Search

    Tony Hoevenaars; Ian Evans; Andy Lawson

    2010-01-01

    To address concerns associated with electrical power system harmonic distortion on ships and offshore oil rigs and platforms, marine regulating bodies have introduced strict new harmonic standards. These standards define the acceptable level of harmonic voltage distortion allowed on the vessels they certify. High-harmonic distortion levels are appearing as a result of the increased use of power-electronic drive converters for

  12. Molecular dynamics probed using high harmonic generation and strong field ionization

    NASA Astrophysics Data System (ADS)

    Li, Wen

    2009-05-01

    The attosecond time-scale electron recollision process that underlies high harmonic generation has uncovered extremely rapid electronic dynamics in atoms and diatomics. We show that high harmonic generation can reveal coupled electronic and nuclear dynamics in polyatomic molecules. By exciting large amplitude vibrations in dinitrogen tetraoxide, we show that tunnel ionization accesses the ground state of the ion at the outer turning point of the vibration, but populates the first excited state at the inner turning point. This state switching mechanism is manifested as bursts of high harmonic light emitted mostly at the outer turning point. Theoretical calculations attribute the large modulation to suppressed emission from the first excited state of the ion. More broadly, these results show that high harmonic generation and strong field ionization in polyatomic molecules undergoing bonding or configurational changes involve the participation of multiple molecular orbitals. We also probe the electron rearrangement in a chemical reaction using strong field ionization. Electronic dynamics play the central role in a chemical reaction. It is extremely desirable for a detection technique to have the capability of probing the ultrafast electronic motion. Time resolved photoelectron spectroscopy can provide some insights. However, the most direct information of electronic dynamics such as the electron configurational change remains elusive. Recently, strong field ionization has been demonstrated to probe the static electron density distribution of the HOMO orbital. We report the preliminary results of applying strong field ionization as a probe to study the electron rearrangement in the photodissociation of bromine. This technique provides more complete information on reaction dynamics and is very promising of making movies of chemical reactions in atomic level.

  13. FTIR, FT-Raman spectra and ab initio DFT vibrational analysis of 2,4-dichloro-6-nitrophenol.

    PubMed

    Sundaraganesan, N; Anand, B; Dominic Joshua, B

    2006-12-01

    The FTIR and FT-Raman spectra of 2,4-dichloro-6-nitrophenol (2,4-DC6NP) has been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of (2,4-DC6NP) were obtained by the ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-31G(d,p) and 6-311+G(d,p) basis sets. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms. PMID:16716652

  14. First-principles study of the phonon vibrational spectra and thermal properties of hexagonal MoS2

    NASA Astrophysics Data System (ADS)

    Yuan, Jiaonan; Lv, Zhenlong; Lu, Qing; Cheng, Yan; Chen, Xiangrong; Cai, Lingcang

    2015-02-01

    The phonon spectra and thermal properties of the hexagonal MoS2 are investigated by using first-principles calculations within the density functional theory (DFT). Finite displacement method is used to calculate the phonon vibrational spectra and phonon density of states. The vibrational modes at the Gamma point are analyzed by using group theory. The temperature and pressure dependence of its thermal quantities such as the thermal expansion, the heat capacity at constant volume, the Gibbs energy and entropy are obtained based on the quasi-harmonic approximation (QHA). Our results show that both the thermal expansion coefficient ? and the heat capacity CV increase with T3 at low temperatures and gradually turn almost linear as the temperature increases. It is found that the entropy is sensitive to the temperature while the Gibbs free energy is more sensitive to the pressure change.

  15. Vibrational echo spectroscopy: Spectral selectivity from vibrational coherence

    NASA Astrophysics Data System (ADS)

    Rector, K. D.; Zimdars, David; Fayer, M. D.

    1998-10-01

    Theory and experimental data are presented which illustrate a new method for performing two-dimensional vibrational spectroscopy using ultrafast pulsed infrared lasers, called vibrational echo spectroscopy (VES). The VES technique can generate a vibrational spectrum with background suppression using the nonlinear vibrational echo pulse sequence. The vibrational echo pulse sequence is used with the delay between the excitation pulses fixed while the excitation wavelength is varied. A detailed theory of VES is presented which calculates the full third order nonlinear polarization including rephasing and nonrephasing diagrams. Finite width laser pulses are used and the calculations are performed for a model spectrum with two or more peaks. Two mechanisms that can result in background and peak suppression are illustrated. The mechanisms are based on differences in homogeneous dephasing times (T2) or transition dipole matrix element magnitudes. Although the VES line shape differs from the absorption line shape, it is possible to recover the absorption line shape from the VES. The method is demonstrated experimentally on the vibrational mode of CO (center at 1945 cm-1) bound to the active site of the protein myoglobin (Mb-CO). The protein and solvent produce a large absorption background while the VES spectrum of Mb-CO is background free. Calculations are able to reproduce the experimental Mb-CO VES line shape.

  16. Vibrational spectroscopy of Methyl benzoate.

    PubMed

    Maiti, Kiran Sankar

    2015-08-14

    Methyl benzoate is studied as a model compound for the development of new IR pulse schemes with possible applicability to biomolecules. Anharmonic vibrational modes of Methyl benzoate are calculated on different level (MP2, SCS, CCSD(T) with varying basis sets) ab initio PESs using the vibrational self-consistent field (VSCF) method and its correlation corrected extensions. Dual level schemes, combining different quantum chemical methods for diagonal and coupling potentials, are systematically studied and applied successfully to reduce the computational cost. Isotopic substitution of ?-hydrogen by deuterium is studied to obtain a better understanding of the molecular vibrational coupling topology. PMID:26050760

  17. Vibrational overtone spectroscopy, energy levels, and intensities of (CH3)3C-C?C-H.

    PubMed

    Perez-Delgado, Yasnahir; Barroso, Jenny Z; Garofalo, Lauren A; Manzanares, Carlos E

    2012-03-01

    The vibrational overtone spectra of the acetylenic (?? = 4, 5) and methyl (?? = 5, 6) C-H stretch transitions of tert-butyl acetylene [(CH(3))(3)C-C?C-H] were obtained using the phase shift cavity ring down (PS-CRD) technique at 295 K. The C-H stretch fundamental and overtone absorptions of the acetylenic (?? = 2 and 3) and methyl (?? = 2-4) C-H bonds have been obtained using a Fourier transform infrared and near-infrared spectrophotometer. Harmonic frequency ?(?(1)) and anharmonicities x(?(1)) and x(?(1), ?(24)) are reported for the acetylenic C-H bond. Molecular orbital calculations of geometry and vibrational frequencies were performed. A harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. Band strength values were obtained experimentally and compared with intensities calculated in terms of the HCAO model where only the C-H modes are considered. No adjustable parameters were used to get order of magnitude agreement with experimental intensities for all pure local mode C-H transitions. PMID:22263573

  18. Relativistic harmonic oscillator and space curvature

    Microsoft Academic Search

    Jean Pierre Gazeau; Jacques Renaud

    1993-01-01

    Using simple group theoretical arguments we show how introducing a curvature parameter kappa = omega\\/c for a harmonic oscillator of mass m and frequency omega leads to an elementary entity of energy E0 = mc2 + 1\\/2ℏomega + O(kappa). This entity is a deformation of both an elementary vibration (rest energy 1\\/2ℏomega) and an elementary particle (rest energy mc2).

  19. Calculation of infrared and Raman vibration modes of magnesite at high pressure by density-functional perturbation theory and comparison with experiments

    NASA Astrophysics Data System (ADS)

    Clark, Stewart J.; Jouanna, Paul; Haines, Julien; Mainprice, David

    2011-03-01

    We predict the IR-TO, IR-LO and Raman modes (wave numbers and intensities) of magnesite (MgCO3) up to 50 GPa, at T = 0 K, using the density-functional perturbation theory up to a third order perturbation, under the harmonic assumption. The predicted IR-TO and Raman mode wave numbers, the mode Grüneisen parameters and the Davydov splittings are systematically compared with experimental data for all modes up to the pressures of 10-30 GPa and for some modes up to 50 GPa. Existing experiments allow extending this comparison only to IR-LO wave numbers of the E u (?3) asymmetric-stretch mode, confirming the odd experimental behavior of this mode at very high pressures. Predicted IR-TO, IR-LO and Raman intensities up to 50 GPa are just tabulated, but data are missing for their comparison with precise experiments. However, the generally good agreement observed between numerical results and experimental data, when their comparison is possible, suggests that first-principles methods are a major help to predict the entire spectrum up to very high pressures.

  20. Nuclear signatures on the molecular harmonic emission and the attosecond pulse generation.

    PubMed

    Feng, Liqiang; Chu, Tianshu

    2012-02-01

    In this paper, we theoretically investigate the nuclear signatures effects, i.e., the initial vibrational state and the isotopic effects on the generations of the molecular high-order harmonics and the attosecond pulses when the model H(2)(+)/D(2)(+) ions are exposed to a 5 fs/800 nm chirp pulse. The numerical solution of the time-dependent Schrödinger equation for these vibrating molecule ions shows that the intensities of the harmonic spectra are reinforced with the enhancement of the initial vibrational state. Moreover, through the investigation of the isotopic effect, we find that more intense harmonics are generated in the lighter nucleus. Furthermore, by optimizing the chirp pulse under the optimal initial vibrational state, an intense ultrabroad supercontinuum with a 325 eV bandwidth can be obtained. By properly superposing the harmonic spectrum, an attosecond pulse as short as 57 as (16 as) is generated without (with) phase compensation. PMID:22320720

  1. Calculation of Raman intensities for the ring-puckering vibrations of 2,5-dihydropyrrole and trimethyleneimine. Electrical versus mechanical anharmonicity in asymmetric potential wells

    NASA Astrophysics Data System (ADS)

    Bocian, David F.; Schick, G. Alan; Birge, Robert R.

    1981-09-01

    Raman intensities are calculated for the ring-puckering transitions of 2,5-dihydropyrrole (DHP) and trimethyleneimine (TMI) using an anisotropic atom-point dipole interaction model to evaluate the elements of the molecular polarizability tensor. The calculated relative intensities for the members of the ?v = 1 and ?v = 2 ring-puckering progressions for DHP are in good agreement with those observed. The calculations predict that the observed ?v = 2 overtones of DHP occur not because of the first-order allowedness expected for these transitions in the asymmetric double-minimum potential well which governs the ring-puckering motion, but rather because of unusually large second-order terms in the expansions of the polarizability tensor elements in the puckering coordinate [?(?2???/?Z2)0??0]. Raman intensities are calculated for the ring-puckering transitions of TMI using the two different potential functions which have been proposed for the puckering motion. It is found that the intensities calculated for the slightly asymmetric double-minimum potential V(Z) = (0.922 05×106)Z4-(0.379 44×105)Z2+(0.159 13×105)Z 3 proposed by Carreira and Lord [J. Chem. Phys. 51, 2735 (1969)] cannot be reconciled with experiment. On the other hand, the intensities calculated for the highly asymmetric single-minimum potential V(Z) = (0.7553×105)Z2-(0.4336×106)Z3+(0.7035×106)Z4 proposed by Robiette et al. [Mol. Phys. 42,1519 (1981)] are in excellent agreement with experiment. Our calculations confirm that the three most intense ring-puckering transitions observed in the Raman (and far-infrared) spectrum of TMI are the lowest members of a ?v = 1 rather than a ?v = 2 progression. The calculations further indicate that high-order electrical terms in the polarizability expansions contribute significantly to the Raman intensities of both the ?v = 1 and ?v = 2 ring-puckering progressions. Neglect of the electrically anharmonic terms in the intensity calculation for the single-minimum well results in a significant disparity between calculation and experiment.

  2. SHTOOLS: Tools for Working with Spherical Harmonics

    NASA Astrophysics Data System (ADS)

    Wieczorek, Mark

    2011-10-01

    SHTOOLS is an archive of fortran 95 based software that can be used to perform (among others) spherical harmonic transforms and reconstructions, rotations of spherical harmonic coefficients, and multitaper spectral analyses on the sphere. While several collections of code currently exist for working with data expressed in spherical harmonics, this one is unique for several reasons: It can accommodate any standard normalization of the spherical harmonic functions ("geodesy" 4? normalized, Schmidt semi-normalized, orthonormalized, and unnormalized).Either real or complex spherical harmonics can be employed.Spherical harmonic transforms are calculated by exact quadrature rules using either (1) the sampling theorem of Driscoll and Healy (1994) where data are equally sampled (or spaced) in latitude and longitude, or (2) Gauss-Legendre quadrature. A least squares inversion routine for irregularly sampled data is included as well.One can choose to use or exclude the Condon-Shortley phase factor of (-1)m with the associated Legendre functions.The spherical harmonic transforms are proven to be accurate to approximately degree 2800, corresponding to a spatial resolution of better than 4 arc minutes.Routines are included for performing localized multitaper spectral analyses.Routines are included for performing standard gravity calculations, such as computation of the geoid and the determination of the potential associated with finite-amplitude topography.The routines are fast. Spherical harmonic transforms and reconstructions take on the order of 1 second for bandwidths less than 600 and about 3 minutes for bandwidths close to 2800.

  3. Photothermal Study of Free and Forced Elastic Vibrations of Microcantilevers

    NASA Astrophysics Data System (ADS)

    Todorovic, D. M.; Cretin, B.; Vairac, P.; Song, Y.; Rabasovic, M. D.; Markushev, D. D.

    2015-01-01

    Dynamic free (spontaneous) and forced (optically excited) elastic vibration spectra of a cantilever (CL) were studied. The amplitude and phase elastic displacements of silicon CLs were measured as a function of the modulation frequency with and without optical excitation. Typically, four obvious peaks can be observed in the elastic vibration spectrum. The first peak represents the forced vibrations at the same frequency as the modulation of laser excitation, while two other peaks are the third and fifth harmonics. One small peak is the first natural resonance of the CL (free vibrations, spontaneous vibrations). The amplitude of elastic vibrations without optical excitation changes with frequency, and it is possible to distinguish two frequency regions. In the high frequency range above 10 kHz, the amplitude elastic vibration spectra are not a function of the frequency which is typically for white noise. The white noise level, which corresponds to the thermomechanical noise, was found. The forced vibrations are precisely studied by modulated optical excitation where the frequency is varied from 3 kHz to 45 kHz and by measuring the response with a lock-in-amplifier (measuring the amplitude and phase of the elastic vibrations). The optically excited elastic vibrations are the consequence of thermal and electronic elastic effects in the silicon CL. The mechanical response of the optically excited CL was modeled with good approximation by a damped harmonic oscillator. The experimental amplitude and phase spectra were fitted with theoretical curves, and the quality factor near the natural (resonance) frequency was obtained.

  4. Long transient phenomenon in nonlinear structural vibration

    NASA Astrophysics Data System (ADS)

    Frank Pai, P.

    2009-03-01

    The long transient phenomenon in nonlinear structural vibrations is examined in detail by using a signal decomposition and processing method based on the empirical mode decomposition, Hilbert-Huang transform (HHT), and nonlinear dynamic characteristics derived from perturbation analysis. A sliding-window fitting (SWF) technique is derived to show the physical implication of Hilbert-Huang transform and other time-frequency decomposition methods. The SWF uses windowed regular harmonics and function orthogonality to simultaneously extract time-localized regular and/or distorted harmonics. Because of the use of pre-determined basis functions, function orthogonality, and windowed curve fitting for component extraction, it cannot extract accurate time-varying frequencies and amplitudes of harmonics distorted by nonlinearities. On the other hand, the HHT uses the apparent time scales revealed by the signal's local maxima and minima to sequentially sift distorted harmonics of different time scales, starting from high-frequency to low-frequency ones. Because Hilbert-Huang transform does not use predetermined basis functions and function orthogonality for component extraction, it provides more accurate signal decomposition and instant amplitudes and frequencies of extracted distorted harmonics. Numerical results show that the proposed HHT-based signal decomposition and processing method can accurately decompose nonlinear nonstationary signals and extract accurate intrawave amplitude and phase modulations, distorted harmonic response under a single-frequency harmonic excitation, and different types and orders of nonlinearities. Using this signal processing method, the long transient phenomenon in nonlinear vibrations is found to be caused by nonlinearities, coupling of transient and forced vibrations, and/or modal coupling of multiple modes.

  5. Optimal Vibration Control of Vehicle Engine-Body System using Haar Functions

    Microsoft Academic Search

    Hamid Reza Karimi

    2006-01-01

    In this note a method of designing optimal vibration control based on Haar functions to control of bounce and pitch vibrations in engine-body vibration structure is presented. Utilizing properties of Haar functions, a computational method to find optimal vibration control for the engine-body system is developed. It is shown that the optimal state trajectories and optimal vibration control are calculated

  6. Interpreting vibrationally resolved spectra of molecular dications (doubly positively charged molecules): HCl

    Microsoft Academic Search

    FREDERICK R. BENNETT; ANDREW D. J. CRITCHLEY; GEORGE C. KING; ROBERT J. LeROY; IAIN R. McNAB

    1999-01-01

    Vibrationally resolved spectra of HCl appear to show five vibrational levels for the X? ground electronic state, whereas calculations of vibrational levels supported by ab initio potential energy curves have been able to locate only three vibrational levels below the barrier; this discrepancy is resolved by considering vibrational states that the potential function supports in the continuum above the barrier

  7. Interpreting vibrationally resolved spectra of molecular dications (doubly positively charged molecules): HCl2+

    Microsoft Academic Search

    Frederick R. Bennett; Andrew D. J. Critchley; George C. King; Robert J. Leroy; Iain R. McNab

    1999-01-01

    Vibrationally resolved spectra of HCl2+ appear to show five vibrational levels for the X3- ground electronic state, whereas calculations of vibrational levels supported by ab initio potential energy curves have been able to locate only three vibrational levels below the barrier; this discrepancy is resolved by considering vibrational states that the potential function supports in the continuum above the barrier

  8. Conformational stability, vibrational and NMR analysis, chemical potential and thermodynamical parameter of 3-tert-butyl-4-hydroxyanisole.

    PubMed

    Balachandran, V; Karpagam, V; Revathi, B; Kavimani, M; Santhi, G

    2015-01-25

    The FT-IR and FT-Raman spectra of 3-tert-butyl-4-hydroxyanisole (TBHA) molecule have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. Optimized geometrical structure, harmonic vibrational frequencies has been computed by B3LYP level using 6-31G (d,p) and 6-311+G (d,p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the first-order hyperpolarizability of the investigated molecule were computed using DFT calculations. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and analyzed. The isotropic chemical shift computed by (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the TBHA calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations. PMID:25173520

  9. Conformational stability, vibrational and NMR analysis, chemical potential and thermodynamical parameter of 3-tert-butyl-4-hydroxyanisole

    NASA Astrophysics Data System (ADS)

    Balachandran, V.; Karpagam, V.; Revathi, B.; Kavimani, M.; Santhi, G.

    2015-01-01

    The FT-IR and FT-Raman spectra of 3-tert-butyl-4-hydroxyanisole (TBHA) molecule have been recorded in the region 4000-400 cm-1 and 3500-100 cm-1, respectively. Optimized geometrical structure, harmonic vibrational frequencies has been computed by B3LYP level using 6-31G (d, p) and 6-311 + G (d, p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the first-order hyperpolarizability of the investigated molecule were computed using DFT calculations. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and analyzed. The isotropic chemical shift computed by 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the TBHA calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations.

  10. Monitoring molecular dynamics using coherent electrons from high harmonic generation

    PubMed Central

    Wagner, Nicholas L.; Wüest, Andrea; Christov, Ivan P.; Popmintchev, Tenio; Zhou, Xibin; Murnane, Margaret M.; Kapteyn, Henry C.

    2006-01-01

    We report a previously undescribed spectroscopic probe that makes use of electrons rescattered during the process of high-order harmonic generation. We excite coherent vibrations in SF6 using impulsive stimulated Raman scattering with a short laser pulse. A second, more intense laser pulse generates high-order harmonics of the fundamental laser, at wavelengths of ?20–50 nm. The high-order harmonic yield is observed to oscillate, at frequencies corresponding to all of the Raman-active modes of SF6, with an asymmetric mode most visible. The data also show evidence of relaxation dynamics after impulsive excitation of the molecule. Theoretical modeling indicates that the high harmonic yield should be modulated by both Raman and infrared-active vibrational modes. Our results indicate that high harmonic generation is a very sensitive probe of vibrational dynamics and may yield more information simultaneously than conventional ultrafast spectroscopic techniques. Because the de Broglie wavelength of the recolliding electron is on the order of interatomic distances, i.e., ?1.5 Å, small changes in the shape of the molecule lead to large changes in the high harmonic yield. This work therefore demonstrates a previously undescribed spectroscopic technique for probing ultrafast internal dynamics in molecules and, in particular, on the chemically important ground-state potential surface. PMID:16895984

  11. Molecular structure, vibrational spectra, AIM, HOMO-LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree-Fock and density functional theory

    NASA Astrophysics Data System (ADS)

    Issaoui, Noureddine; Ghalla, Houcine; Muthu, S.; Flakus, H. T.; Oujia, Brahim

    2015-02-01

    In this work, the molecular structure, harmonic vibrational frequencies, UV, NBO and AIM of 3-thiophenecarboxilic acid (abbreviated as 3-TCA) monomer and dimer has been investigated. The FT-IR and FT-Raman spectra were recorded. The ground-state molecular geometry and vibrational frequencies have been calculated by using the Hartree-Fock (HF) and density functional theory (DFT)/B3LYP methods and 6-311++G(d,p) as a basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with VEDA program. Comparison of the observed fundamental vibrational frequencies of 3-TCA with calculated results by HF and DFT methods indicates that B3LYP is better to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title compound have been constructed. A study on the Mulliken atomic charges, the electronic properties were performed by time-dependent DFT (TD-DFT) approach, frontier molecular orbitals (HOMO-LUMO), molecular electrostatic potential (MEP) and thermodynamic properties have been performed. The electric dipole moment (?) and the first hyperpolarizability (?) values of the investigated molecule have been also computed.

  12. Molecular structure, vibrational spectra, AIM, HOMO-LUMO, NBO, UV, first order hyperpolarizability, analysis of 3-thiophenecarboxylic acid monomer and dimer by Hartree-Fock and density functional theory.

    PubMed

    Issaoui, Noureddine; Ghalla, Houcine; Muthu, S; Flakus, H T; Oujia, Brahim

    2014-10-16

    In this work, the molecular structure, harmonic vibrational frequencies, UV, NBO and AIM of 3-thiophenecarboxilic acid (abbreviated as 3-TCA) monomer and dimer has been investigated. The FT-IR and FT-Raman spectra were recorded. The ground-state molecular geometry and vibrational frequencies have been calculated by using the Hartree-Fock (HF) and density functional theory (DFT)/B3LYP methods and 6-311++G(d,p) as a basis set. The fundamental vibrations were assigned on the basis of the total energy distribution (TED) of the vibrational modes, calculated with VEDA program. Comparison of the observed fundamental vibrational frequencies of 3-TCA with calculated results by HF and DFT methods indicates that B3LYP is better to HF method for molecular vibrational problems. The difference between the observed and scaled wavenumber values is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title compound have been constructed. A study on the Mulliken atomic charges, the electronic properties were performed by time-dependent DFT (TD-DFT) approach, frontier molecular orbitals (HOMO-LUMO), molecular electrostatic potential (MEP) and thermodynamic properties have been performed. The electric dipole moment (?) and the first hyperpolarizability (?) values of the investigated molecule have been also computed. PMID:25456664

  13. The harmonic oscillator and nuclear physics

    NASA Technical Reports Server (NTRS)

    Rowe, D. J.

    1993-01-01

    The three-dimensional harmonic oscillator plays a central role in nuclear physics. It provides the underlying structure of the independent-particle shell model and gives rise to the dynamical group structures on which models of nuclear collective motion are based. It is shown that the three-dimensional harmonic oscillator features a rich variety of coherent states, including vibrations of the monopole, dipole, and quadrupole types, and rotations of the rigid flow, vortex flow, and irrotational flow types. Nuclear collective states exhibit all of these flows. It is also shown that the coherent state representations, which have their origins in applications to the dynamical groups of the simple harmonic oscillator, can be extended to vector coherent state representations with a much wider range of applicability. As a result, coherent state theory and vector coherent state theory become powerful tools in the application of algebraic methods in physics.

  14. State-to-state rotational phase coherence effect on the vibration-rotation band shape - An accurate quantum calculation for CO-He

    NASA Technical Reports Server (NTRS)

    Boissoles, J.; Boulet, C.; Robert, D.; Green, S.

    1989-01-01

    Accurate coupled state calculations of line coupling are performed for infrared lines of carbon monoxide perturbed by helium. Such calculations lead to both real and imaginary line couplings. For the first time, the effect of this imaginary line couplings, connected with state-to-state rotational phase coherences, on infrared band shape, is analyzed. An extension of detailed balance principle to the complex plane is suggested from the present computed off-diagonal cross sections. This allows us to understand the physical mechanism underlying the weak effect of phase coherences on CO-He infrared band shape.

  15. Color harmonization for images

    NASA Astrophysics Data System (ADS)

    Tang, Zhen; Miao, Zhenjiang; Wan, Yanli; Wang, Zhifei

    2011-04-01

    Color harmonization is an artistic technique to adjust a set of colors in order to enhance their visual harmony so that they are aesthetically pleasing in terms of human visual perception. We present a new color harmonization method that treats the harmonization as a function optimization. For a given image, we derive a cost function based on the observation that pixels in a small window that have similar unharmonic hues should be harmonized with similar harmonic hues. By minimizing the cost function, we get a harmonized image in which the spatial coherence is preserved. A new matching function is proposed to select the best matching harmonic schemes, and a new component-based preharmonization strategy is proposed to preserve the hue distribution of the harmonized images. Our approach overcomes several shortcomings of the existing color harmonization methods. We test our algorithm with a variety of images to demonstrate the effectiveness of our approach.

  16. Vibrational analysis, electronic structure and nonlinear optical properties of Levofloxacin by density functional theory

    NASA Astrophysics Data System (ADS)

    Gunasekaran, Sethu; Rajalakshmi, K.; Kumaresan, Subramanian

    2013-08-01

    The Fourier transform (FT-IR) spectrum of Levofloxacin was recorded in the region 4000-400 cm-1 and a complete vibrational assignment of fundamental vibrational modes of the molecule was carried out using density functional method. The observed fundamental modes have been compared with the harmonic vibrational frequencies computed using DFT (B3LYP) method by employing 6-31 G (d, p) basis sets. The most stable geometry of the molecule under investigation has been determined from the potential energy scan. The first-order hyperpolarizability (?o) and other related properties (?, ?o) of Levofloxacin are calculated using density functional theory (DFT) on a finite field approach. UV-vis spectrum of the molecule was recorded and the electronic properties, such as HOMO and LUMO energies were performed by DFT using 6-31 G (d, p) basis sets. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that, the charge transfer occurs within the molecule. The other molecular properties like molecular electrostatic potential (MESP), Mulliken population analysis and thermodynamic properties of the title molecule have been calculated.

  17. Vibration analyzer

    NASA Technical Reports Server (NTRS)

    Bozeman, Richard J., Jr. (inventor)

    1990-01-01

    The invention relates to monitoring circuitry for the real time detection of vibrations of a predetermined frequency and which are greater than a predetermined magnitude. The circuitry produces an instability signal in response to such detection. The circuitry is particularly adapted for detecting instabilities in rocket thrusters, but may find application with other machines such as expensive rotating machinery, or turbines. The monitoring circuitry identifies when vibration signals are present having a predetermined frequency of a multi-frequency vibration signal which has an RMS energy level greater than a predetermined magnitude. It generates an instability signal only if such a vibration signal is identified. The circuitry includes a delay circuit which responds with an alarm signal only if the instability signal continues for a predetermined time period. When used with a rocket thruster, the alarm signal may be used to cut off the thruster if such thruster is being used in flight. If the circuitry is monitoring tests of the thruster, it generates signals to change the thruster operation, for example, from pulse mode to continuous firing to determine if the instability of the thruster is sustained once it is detected.

  18. High-order harmonic generation and Fano resonances

    NASA Astrophysics Data System (ADS)

    Strelkov, V. V.; Khokhlova, M. A.; Shubin, N. Yu

    2014-05-01

    We present a high-order harmonic generation theory which generalizes the strong-field approximation to the resonant case when the harmonic frequency is close to that of the transition from the ground state to an autoionizing state of the generating system. We show that the line shape of the resonant harmonic is a product of the Fano-like factor and the harmonic line which would be emitted in the absence of the resonance. The theory predicts rapid variation of the harmonic phase in the vicinity of the resonance. The calculated resonant harmonic phase is in reasonable agreement with recent measurements. Predicting the phase locking of a group of resonantly enhanced harmonics, our theory allows us to study the perspectives of producing an attosecond pulse train using such harmonics.

  19. Vibrational assignment and crystal structure of 3-amino-1-phenyl-2-buten-1-one

    NASA Astrophysics Data System (ADS)

    Tayyari, Sayyed Faramarz; Ghafari, Maliheh; Jamialahmadi, Mina; Chahkandi, Behzad; Patrick, Brian O.; Wang, Yan Alexander

    2013-08-01

    3-Amino-1-phenyl-2-buten-1-one (APBO) was synthesized by amination of benzoylacetone (BA) and its structure was studied by X-ray crystallographic method. The geometry of APBO was also optimized by means of density functional theory (DFT) and ab initio calculations and the results were compared with the X-ray crystallographic data. The vibrational fundamentals predicted within harmonic model, calculated at the B3LYP/6-311++G**, and by anharmonic model, calculated at the B3LYP/6-31G** level, display excellent agreement with the measured data. The proposed assignments are further confirmed by observing the deuterium isotopic shifts of different bands through predictions by the same theoretical method. The theoretical results obtained for APBO were compared with those of 4-amino-3-penten-2-one (APO).

  20. Vibrational spectra (FT-IR, FT-Raman), frontier molecular orbital, first hyperpolarizability, NBO analysis and thermodynamics properties of Piroxicam by HF and DFT methods

    NASA Astrophysics Data System (ADS)

    Suresh, S.; Gunasekaran, S.; Srinivasan, S.

    2015-03-01

    The solid phase FT-IR and FT-Raman spectra of 4-Hydroxy-2-methyl-N-(2-pyridinyl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide (Piroxicam) have been recorded in the region 4000-400 and 4000-100 cm-1 respectively. The molecular geometry, harmonic vibrational frequencies and bonding features of piroxicam in the ground state have been calculated by Hartree-Fock (HF) and density functional theory (DFT) methods using 6-311++G(d,p) basis set. The calculated harmonic vibrational frequencies are scaled and they are compared with experimental obtained by FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of the title compound has been made on the basis of the calculated potential energy distribution (PED). The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MESP) are also performed. The linear polarizability (?) and the first order hyper polarizability (?) values of the title compound have been computed. The molecular stability arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

  1. Vibrational spectra (FT-IR, FT-Raman), frontier molecular orbital, first hyperpolarizability, NBO analysis and thermodynamics properties of Piroxicam by HF and DFT methods.

    PubMed

    Suresh, S; Gunasekaran, S; Srinivasan, S

    2015-03-01

    The solid phase FT-IR and FT-Raman spectra of 4-Hydroxy-2-methyl-N-(2-pyridinyl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide (Piroxicam) have been recorded in the region 4000-400 and 4000-100cm(-1) respectively. The molecular geometry, harmonic vibrational frequencies and bonding features of piroxicam in the ground state have been calculated by Hartree-Fock (HF) and density functional theory (DFT) methods using 6-311++G(d,p) basis set. The calculated harmonic vibrational frequencies are scaled and they are compared with experimental obtained by FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of the title compound has been made on the basis of the calculated potential energy distribution (PED). The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MESP) are also performed. The linear polarizability (?) and the first order hyper polarizability (?) values of the title compound have been computed. The molecular stability arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. PMID:25523048

  2. The vibrational spectrum of H2O3: An ab initio investigation

    NASA Technical Reports Server (NTRS)

    Jackels, Charles F.

    1991-01-01

    Theoretically determined frequencies and absorption intensities are reported for the vibrational spectrum of the covalent HOOOH and hydrogen bonded HO---HOO intermediates that may form in the reaction of the hydroxyl and hydroperoxyl radicals. Basis sets of DZP quality, augmented by diffuse and second sets of polarization functions have been used with CASSCF wave functions. The calculated harmonic vibrational frequencies of HOOOH have been corrected with empirical factors and presented in the form of a 'stick' spectrum. The oxygen backbone vibrations, predicted to occur at 519, 760, and 870 cm(exp -1), are well separated from most interferences, and may be the most useful for the species' identification. In the case of the hydrogen bonded isomer, emphasis has been placed upon prediction of the shifts in the intramolecular vibrational frequencies that take place upon formation of the complex. In particular, the HO stretch and HOO bend of HO2 are predicted to have shifts of -59 and 53 cm(exp -1), respectively, which should facilitate their identification. It is also noted that the antisymmetric stretching frequency of the oxygen backbone in HOOOH exhibits a strong sensitivity to the degree of electron correlation, such as has been previously observed for the same mode in ozone.

  3. Simple Harmonic Motion in Harmonic Plane Waves.

    ERIC Educational Resources Information Center

    Benumof, Reuben

    1980-01-01

    Discusses the distribution of kinetic and potential energy in transverse and longitudinal waves and examines the transmission of power and momentum. This discussion is intended to aid in understanding the simple harmonic motion of a particle involved in the propagation of a harmonic mechanical plane wave. (HM)

  4. 3D field harmonics

    SciTech Connect

    Caspi, S.; Helm, M.; Laslett, L.J.

    1991-03-30

    We have developed an harmonic representation for the three dimensional field components within the windings of accelerator magnets. The form by which the field is presented is suitable for interfacing with other codes that make use of the 3D field components (particle tracking and stability). The field components can be calculated with high precision and reduced cup time at any location (r,{theta},z) inside the magnet bore. The same conductor geometry which is used to simulate line currents is also used in CAD with modifications more readily available. It is our hope that the format used here for magnetic fields can be used not only as a means of delivering fields but also as a way by which beam dynamics can suggest correction to the conductor geometry. 5 refs., 70 figs.

  5. On Harmonic Superspace

    E-print Network

    P. S. Howe

    1998-12-15

    A short survey of some aspects of harmonic superspace is given. In particular, the $d=3, N=8$ scalar supermultiplet and the $d=6, N=(2,0)$ tensor multiplet are described as analytic superfields in appropriately defined harmonic superspaces.

  6. Conformational stability, vibrational spectra, HOMO-LUMO and NBO analysis of 1,3,4-thiadiazolidine-2,5-dithione with experimental (FT-IR and FT-Raman) techniques and scaled quantum mechanical calculations

    NASA Astrophysics Data System (ADS)

    Xavier, R. John; Dinesh, P.

    2013-09-01

    The experimental and theoretical study on the structure and vibrations of 1,3,4-thiadiazolidine-2,5-dithione (TDZD) is presented. The FT-IR spectra (4000-400 cm-1) and the FT-Raman spectra (4000-50 cm-1) of the title molecule have been recorded. The energies of TDZD were obtained for all the possible four conformers from HF and DFT with 6-311G(d,p) and 6-311++G(d,p) basis set calculations. From the computational results, conformer C4 is identified as the most stable conformers of TDZD. The spectroscopic and theoretical results are compared with the corresponding properties for TDZD of C4 conformer. The temperature dependence of thermodynamic properties has been analyzed. Molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that charge transfer occurs in the molecules. Information about the size, shape, charge density distribution, and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential (ESP). The dipole moment (?) and polarizability (?), anisotropy polarizability (??) and first hyperpolarizability (?total) of the molecule have been reported.

  7. Inelastic and elastic neutron scattering studies of the vibrational and reorientational dynamics, crystal structure and solid-solid phase transition in [Mn(OS(CH3)2)6](ClO4)2 supported by theoretical (DFT) calculations

    NASA Astrophysics Data System (ADS)

    Szostak, El?bieta; Hetma?czyk, Joanna; Migda?-Mikuli, Anna

    2015-06-01

    The vibrational and reorientational dynamics of CH3 groups from (CH3)2SO ligands in the high- and low-temperature phases of [Mn(OS(CH3)2)6](ClO4)2 were investigated by quasielastic and inelastic incoherent neutron scattering (QENS and IINS) methods. The results show that above the phase transition temperature (detected earlier by differential scanning calorimetry (DSC) at TC5c = 222.9 K on cooling and at TC5h = 225.4 K on heating) the CH3 groups perform fast (?R ? 10-12-10-13 s) reorientational motions. These motions start to slow down below TC5c Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS and IINS, indicated that this phase transition is associated with a change of the crystal structure, too. Theoretical infrared absorption, Raman and inelastic incoherent neutron scattering spectra were calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311+G(d,p) basis set (on C, H, S, O atoms) for the isolated equilibrium model (isolated [Mn(DMSO)6]2+ cation and ClO4- anion). Calculated spectra show a good agreement with the experimental spectra (FT-IR, RS and IINS). The comparison of the results obtained by these complementary methods was made.

  8. Temperature effects in first-principles solid state calculations of the chemical shielding tensor made simple.

    PubMed

    Monserrat, Bartomeu; Needs, Richard J; Pickard, Chris J

    2014-10-01

    We study the effects of atomic vibrations on the solid-state chemical shielding tensor using first principles density functional theory calculations. At the harmonic level, we use a Monte Carlo method and a perturbative expansion. The Monte Carlo method is accurate but computationally expensive, while the perturbative method is computationally more efficient, but approximate. We find excellent agreement between the two methods for both the isotropic shift and the shielding anisotropy. The effects of zero-point quantum mechanical nuclear motion are important up to relatively high temperatures: at 500 K they still represent about half of the overall vibrational contribution. We also investigate the effects of anharmonic vibrations, finding that their contribution to the zero-point correction to the chemical shielding tensor is small. We exemplify these ideas using magnesium oxide and the molecular crystals L-alanine and ?-aspartyl-L-alanine. We therefore propose as the method of choice to incorporate the effects of temperature in solid state chemical shielding tensor calculations using the perturbative expansion within the harmonic approximation. This approach is accurate and requires a computational effort that is about an order of magnitude smaller than that of dynamical or Monte Carlo approaches, so these effects might be routinely accounted for. PMID:25296790

  9. Double-Coupled Dynamics for the Electromechanical Integrated Electrostatic Harmonic Drive

    Microsoft Academic Search

    Lizhong Xu; Cuirong Zhu; Lei Qin

    2008-01-01

    In this paper, considering bending vibration as a perturbation for extension vibration of the ring, the double-coupled dynamic equations of the electromechanical integrated electrostatic harmonic drive are presented. In the equations, electromechanical coupling and extension-bending coupling are included. Based on static displacements, dynamic electromechanical coupled forces are determined. Substituting the dynamic electromechanical coupled force into dynamic equations, and using the

  10. Indoor imaging of targets enduring simple harmonic motion using Doppler radars

    Microsoft Academic Search

    Pawan Setlur; Moeness Amin; Fauzia Ahmad; Thayananthan Thayaparan

    2005-01-01

    In this paper, we demonstrate the micro-Doppler signatures of rotational\\/vibrational targets enduring simple harmonic motions (SHM). The SHM, whether it represents vibrations or rotations, induces frequency modulations on radar returns. The returns capture certain extrinsic motion characteristics of the target which have a sinusoidal instantaneous frequency. Indoor imaging data collection experiments have been performed. The experiments have been designed, keeping

  11. Harmonization of Biodiesel Specifications

    SciTech Connect

    Alleman, T. L.

    2008-02-01

    Worldwide biodiesel production has grown dramatically over the last several years. Biodiesel standards vary across countries and regions, and there is a call for harmonization. For harmonization to become a reality, standards have to be adapted to cover all feedstocks. Additionally, all feedstocks cannot meet all specifications, so harmonization will require standards to either tighten or relax. For harmonization to succeed, the biodiesel market must be expanded with the alignment of test methods and specification limits, not contracted.

  12. Quantum chemical vibrational study, molecular property, FTIR, FT-Raman spectra, NBO, HOMO-LUMO energies and thermodynamic properties of 1-methyl-2-phenyl benzimidazole.

    PubMed

    Karnan, M; Balachandran, V; Murugan, M; Murali, M K

    2014-09-15

    The solid phase FT-IR and FT-Raman spectra of 1-methyl-2-phenyl benzimidazole (MPBZ) have been recorded in the condensed state. In this work, experimental and theoretical study on the molecular structure, quantum chemical calculations of energies and vibrational wavenumbers of MPBZ is presented. The vibrational frequencies of the title compound were obtained theoretically by DFT/B3LYP calculations employing the standard 6-311+G(d,p) and 6-311++G(d,p) basis set for optimized geometry and were compared with Fourier transform infrared spectrum (FTIR) in the region of 4000-400 cm(-1) and with Fourier transform Raman spectrum in the region of 4000-100 cm(-1). Complete vibrational assignments, analysis and correlation of the fundamental modes for the title compound were carried out. The vibrational harmonic frequencies were scaled using scale factor, yielding a good agreement between the experimentally recorded and the theoretically calculated values. The study is extended to calculate the HOMO-LUMO energy gap, NBO, mapped molecular electrostatic potential (MEP) surfaces, polarizability, Mulliken charges and thermodynamic properties of the title compound. PMID:24785089

  13. Quantum chemical vibrational study, molecular property, FTIR, FT-Raman spectra, NBO, HOMO-LUMO energies and thermodynamic properties of 1-methyl-2-phenyl benzimidazole

    NASA Astrophysics Data System (ADS)

    Karnan, M.; Balachandran, V.; Murugan, M.; Murali, M. K.

    2014-09-01

    The solid phase FT-IR and FT-Raman spectra of 1-methyl-2-phenyl benzimidazole (MPBZ) have been recorded in the condensed state. In this work, experimental and theoretical study on the molecular structure, quantum chemical calculations of energies and vibrational wavenumbers of MPBZ is presented. The vibrational frequencies of the title compound were obtained theoretically by DFT/B3LYP calculations employing the standard 6-311+G(d,p) and 6-311++G(d,p) basis set for optimized geometry and were compared with Fourier transform infrared spectrum (FTIR) in the region of 4000-400 cm-1 and with Fourier transform Raman spectrum in the region of 4000-100 cm-1. Complete vibrational assignments, analysis and correlation of the fundamental modes for the title compound were carried out. The vibrational harmonic frequencies were scaled using scale factor, yielding a good agreement between the experimentally recorded and the theoretically calculated values. The study is extended to calculate the HOMO-LUMO energy gap, NBO, mapped molecular electrostatic potential (MEP) surfaces, polarizability, Mulliken charges and thermodynamic properties of the title compound.

  14. Harmonic synchronizations of spacetime

    SciTech Connect

    Bona, C.; Masso, J.

    1988-10-15

    The spacetime slicings associated with a harmonic time coordinate (harmonic synchronizations) are considered and their usefulness in the field of numerical relativity is studied. Harmonic synchronizations are shown to avoid singularities in the same way that the widely used maximal slicings do. Both kinds of slicing are compared in stationary axisymmetric spacetimes, homogeneous cosmological models, and Kerr-Newman black holes.

  15. Tissue harmonic imaging

    Microsoft Academic Search

    Michalakis A. Averkiou

    2000-01-01

    Harmonic imaging was originally developed for microbubble contrast agents in the early 90s under the assumption that tissue is linear and all harmonic echoes are generated by the bubbles. In fact, tissue, like bubbles, is a nonlinear medium. Whereas the harmonic echoes from bubbles have their origins in nonlinear scattering, those from tissue are a result of nonlinear propagation. The

  16. Tissue harmonic ultrasonic imaging

    Microsoft Academic Search

    Michalakis A. Averkiou

    2001-01-01

    Harmonic imaging was originally developed for microbubble contrast agents in the early 90s under the assumption that tissue is linear and all harmonic echoes are generated by the bubbles. In fact, tissue, like bubbles, is a nonlinear medium. Whereas the harmonic echoes from bubbles have their origins in nonlinear scattering, those from tissue are a result of nonlinear propagation. The

  17. HARMONIC ANALYSIS TERENCE TAO

    E-print Network

    Tao, Terence

    HARMONIC ANALYSIS TERENCE TAO Analysis in general tends to revolve around the study of general functions as input, and return some other function as output). Harmonic analysis1 focuses in particular Strictly speaking, this sentence describes the field of real-variable harmonic analysis. There is another

  18. Molecular structure, intramolecular hydrogen bonding and vibrational spectral investigation of 2-fluoro benzamide - A DFT approach

    NASA Astrophysics Data System (ADS)

    Krishnakumar, V.; Murugeswari, K.; Surumbarkuzhali, N.

    2013-10-01

    The FTIR and FT-Raman spectra of 2-fluoro benzamide (2FBA) have been recorded in the region 4000-400 and 4000-100 cm-1, respectively. The structural analysis, hydrogen bonding, optimized geometry, frequency and intensity of the vibrational bands of 2FBA were obtained by the density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G** basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The 13C NMR spectra have been recorded and 13C nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method and their respective linear correlations were obtained. The electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The Mulliken charges, the values of electric dipole moment (?) of the molecule were computed using DFT calculations. The change in electron density (ED) in the ?* antibonding orbitals and stabilization energies E(2) have been calculated by natural bond (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interactions.

  19. The heme protein low frequency vibrational motions by self consistent normal mode analysis

    NASA Astrophysics Data System (ADS)

    Guo, Jianguang

    Vibrational dynamics of iron active sites in heme proteins and heme model compounds have been studied by normal mode analysis (NMA) and self consistent normal mode analysis (SCNMA). NMA is first used to identify and characterize the iron vibrational modes of the heme model Iron (II)octaethylporphyrin Fe(OEP), and the heme c type cytochrome f. The NMA, in conjunction with NRVS data, provides a good set of refined low temperature force constants. Then, SCNMA is applied to heme c type cytochrome f to study temperature dependent protein motion. Classical NMA assumes harmonic behavior and the protein mean square displacement (MSD) has a linear dependence on temperature. This is only consistent with low temperature experimental results. To connect the protein vibrational motions between low temperature and physiological temperature, we have incorporated a fitted set of anharmonic potentials into SCNMA. In addition, Quantum Harmonic Oscillator (QHO) theory has been used to calculate the displacement distribution for individual vibrational modes. We find that the modes involving soft bonds exhibit significant non-Gaussian dynamics at physiological temperature, which suggests it may be the cause of the non-Gaussian behavior of the protein motions probed by Elastic Incoherent Neutron Scattering (EINS). The combined theory displays a dynamical transition caused by the softening of few "torsional" modes in the low frequency regime (< 50cm-1 or < 6meV or > 0.6ps). These modes change from Gaussian to a classical distribution upon heating. Our theory provides an alternative way to understand the microscopic origin of the protein dynamical transition.

  20. Structural study, coordinated normal analysis and vibrational spectra of 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone.

    PubMed

    Lizárraga, Emilio; Romano, Elida; Rudyk, Roxana Amelia; Catalán, César Atilio Nazareno; Brandán, Silvia Antonia

    2012-11-01

    Structural and vibrational properties of 4-hydroxy-3-(3-methyl-2-butenyl)acetophenone, isolated from Senecio nutans Sch. Bip. (Asteraceae) were studied by infrared and Raman spectroscopies in solid phase. The Density Functional Theory (DFT) method together with Pople's basis set show seven stable conformers for the compound in the gas phase and that only two conformations are probably present in the solid phase. The harmonic vibrational wavenumbers for the optimized geometry were calculated at B3LYP/6-31G and B3LYP/6-311++G levels. For a complete assignment of the vibrational spectra, DFT calculations were combined with Pulay´s Scaled Quantum Mechanics Force Field (SQMFF) methodology in order to fit the theoretical wavenumber values to the experimental ones. Then, a complete assignment of all the observed bands in the vibrational spectra was performed. The natural bond orbital (NBO) study reveals the characteristics of the electronic delocalization of the two stable structures, while the corresponding topological properties of electronic charge density were analyzed by employing Bader's Atoms in the Molecules theory (AIM). PMID:22763324

  1. Vibrational spectroscopic (FT-IR and FT-Raman), first-order hyperpolarizablity, HOMO, LUMO, NBO, Mulliken charges and structure determination of 2-bromo-4-chlorotoluene.

    PubMed

    Arunagiri, C; Arivazhagan, M; Subashini, A

    2011-09-01

    The FT-IR and FT-Raman spectra of 2-bromo-4-chlorotoluene (2B4CT) molecule have been recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. Optimized geometrical structures, harmonic vibrational frequencies, intensities, reduced mass, force constants and depolarization ratio have been computed by the B3 based (B3LYP) density functional methods using 6-31+G(d,p) and 6-311++G(d,p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analysed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the values of electric dipole moment (?) and the first-order hyperpolarizability (?) of the investigated molecule were computed using DFT calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The influences of bromine atom, chlorine atom and methyl group on the geometry of benzene and its normal modes of vibrations have also been discussed. PMID:21680229

  2. Molecular structure and spectroscopic characterization of Carbamazepine with experimental techniques and DFT quantum chemical calculations.

    PubMed

    Suhasini, M; Sailatha, E; Gunasekaran, S; Ramkumaar, G R

    2015-04-15

    A systematic vibrational spectroscopic assignment and analysis of Carbamazepine has been carried out by using FT-IR, FT-Raman and UV spectral data. The vibrational analysis were aided by electronic structure calculations - ab initio (RHF) and hybrid density functional methods (B3LYP) performed with standard basis set 6-31G(d,p). Molecular equilibrium geometries, electronic energies, natural bond order analysis, harmonic vibrational frequencies and IR intensities have been computed. A detailed interpretation of the vibrational spectra of the molecule has been made on the basis of the calculated Potential Energy Distribution (PED) by VEDA program. UV-visible spectrum of the compound was also recorded and the electronic properties, such as HOMO and LUMO energies and ?max were determined by HF/6-311++G(d,p) Time-Dependent method. The thermodynamic functions of the title molecule were also performed using the RHF and DFT methods. The restricted Hartree-Fock and density functional theory-based nuclear magnetic resonance (NMR) calculation procedure was also performed, and it was used for assigning the (13)C and (1)H NMR chemical shifts of Carbamazepine. PMID:25682215

  3. Aeroelastic analysis for helicopter rotors with blade appended pendulum vibration absorbers. Mathematical derivations and program user's manual

    NASA Technical Reports Server (NTRS)

    Bielawa, R. L.

    1982-01-01

    Mathematical development is presented for the expanded capabilities of the United Technologies Research Center (UTRC) G400 Rotor Aeroelastic Analysis. This expanded analysis, G400PA, simulates the dynamics of teetered rotors, blade pendulum vibration absorbers and the higher harmonic excitations resulting from prescribed vibratory hub motions and higher harmonic blade pitch control. Formulations are also presented for calculating the rotor impedance matrix appropriate to these higher harmonic blade excitations. This impedance matrix and the associated vibratory hub loads are intended as the rotor blade characteristics elements for use in the Simplified Coupled Rotor/Fuselage Vibration Analysis (SIMVIB). Sections are included presenting updates to the development of the original G400 theory, and material appropriate to the user of the G400PA computer program. This material includes: (1) a general descriptionof the tructuring of the G400PA FORTRAN coding, (2) a detaild description of the required input data and other useful information for successfully running the program, and (3) a detailed description of the output results.

  4. Lattice Vibration Spectra. LXX. Evaluation of IR Reflection Spectra. Model Calculations and Experimental Data of MnCr2O4 Single Crystals

    NASA Astrophysics Data System (ADS)

    Himmrich, J.; Schneider, G.; Zwinscher, J.; Lutz, H. D.

    1991-12-01

    The various evaluation procedures of IR reflection spectra, viz. Kramer-Kronig analyses (KKA), 3 parameter (coTO, g, y) (3 PM), and 4 parameter (?ro, ?LO yro yLO) oscillator-model calculations (4 PM), are compared. For the zone-centre phonon energies, the oscillator parameters ?ro and ?LO of 4 PM as well as the frequencies of the dielectric functions ?" and - Im(l/?), respectively (KKA, 3 PM), are recommended. The pole frequencies of the |?| functions yield too large TO/LO splittings, especially in the case of large damping of the phonons. In the case of asymmetric reststrahlen bands, the use of 4 PM with different damping constants y for the TO and LO phonons is recommended. Computer simulations of the influence of the various oscillator parameters on the reflection spectra as well as the phonon frequencies of spinel-type MnCr2O4 are included

  5. The Study of Damped Harmonic Oscillations Using an Electronic Counter

    ERIC Educational Resources Information Center

    Wadhwa, Ajay

    2009-01-01

    We study damped harmonic oscillations in mechanical systems like the loaded spring and simple pendulum with the help of an oscillation measuring electronic counter. The experimental data are used in a software program that solves the differential equation for damped vibrations of any system and determines its position, velocity and acceleration as…

  6. Pure-tone birdsong by resonance filtering of harmonic overtones

    Microsoft Academic Search

    Gabriël J. L. Beckers; Roderick A. Suthers; Carel Ten Cate

    2003-01-01

    Pure-tone song is a common and widespread phenomenon in birds. The mechanistic origin of this type of phonation has been the subject of long-standing discussion. Currently, there are three hypotheses. (i) A vibrating valve in the avian vocal organ, the syrinx, generates a multifrequency harmonic source sound, which is filtered to a pure tone by a vocal tract filter (\\

  7. Modeling Motion Oscillations Worksheet Solutions 1. A particle executes simple harmonic motion. When the velocity of the particle is a maximum

    E-print Network

    Modeling Motion Oscillations Worksheet Solutions Part I 1. A particle executes simple harmonic mass rests on a horizontal platform which vibrates vertically in simple harmonic motion with period 0 harmonic motion the position is given by the expression x = A cos (t + ). We have A = 0.062 m and = 2/T =

  8. Spectroscopy of Vibrational States in Diatomic Iodine Molecules

    NASA Astrophysics Data System (ADS)

    Mulholland, Mary; Harrill, Charles H.; Smith, R. Seth

    2015-04-01

    This project is focused on understanding the vibrational structure of iodine, which is a homonuclear diatomic molecule. A 20 mW, 532 nm cw diode laser was used to selectively excite neutral iodine molecules to a higher energy electronic state. By performing spectroscopy on the transitions from this state to a lower energy electronic state, the data only showed those vibrational bands which connect the two electronic states. Since a number of vibrational levels are populated in the higher energy electronic state, the transitions to all of the allowed vibrational levels in the lower energy electronic state provided sufficient data to determine the vibrational structures of both states. Emission spectra were collected with an Ocean Optics USB4000 Compact CCD Spectrometer. The spectrometer had a range of 500 - 770 nm with a resolution of approximately 0.5 nm and was sensitive enough to resolve the vibrational states in diatomic iodine molecules. The results were compared to a simple harmonic oscillator model.

  9. NBO analysis and vibrational spectra of 2,6-bis(p-methyl benzylidene cyclohexanone) using density functional theory.

    PubMed

    Padmaja, L; Amalanathan, M; Ravikumar, C; Hubert Joe, I

    2009-10-01

    Vibrational analysis of the 2,6-bis(p-methyl benzylidene cyclohexanone) [PMBC] compound was carried out by using NIR FT-Raman and FT-IR spectroscopic techniques. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of PMBC have been investigated with the help of B3LYP/6-31 G(d) density functional theory method. The optimized geometry clearly demonstrates cyclohexanone ring chair conformation is changed into half-chair conformation. The shortening of C-H bond length and blue shifting of the CH stretching wavenumber suggest the existence of improper weak C-H***O hydrogen bonding, which is confirmed by the natural bond orbital analysis. The Mulliken population analysis on atomic charges and the HOMO-LUMO energy are also calculated. PMID:19640777

  10. Raising and Lowering operators of spin-weighted spheroidal harmonics

    E-print Network

    Abhay G. Shah; Bernard F. Whiting

    2015-03-09

    In this paper we generalize the spin-raising and lowering operators of spin-weighted spherical harmonics to linear-in-$\\gamma$ spin-weighted spheroidal harmonics where $\\gamma$ is an additional parameter present in the second order ordinary differential equation governing these harmonics. One can then generalize these operators to higher powers in $\\gamma$. Constructing these operators required calculating the $\\ell$-, $s$- and $m$-raising and lowering operators (and various combinations of them) of spin-weighted spherical harmonics which have been calculated and shown explicitly in this paper.

  11. A simple curvilinear internal coordinate model for vibrational energy levels of hydrogen sulfide and sulfur dioxide

    Microsoft Academic Search

    Esa Kauppi; Lauri Halonen

    1992-01-01

    A simple curvilinear internal-coordinate Hamiltonian model for vibrational-term values of well-bent XY2 molecules is developed. The stretching vibrations are described in the zero-order picture by Morse oscillators and the bend by a harmonic oscillator. Coupling terms are approximated by harmonic oscillator formulas. Van Vleck perturbation theory is used to transform the Hamiltonian matrix to a block diagonal form. Analytical expressions

  12. Certain characteristics and capture regions of nonlinear vibrating systems

    NASA Technical Reports Server (NTRS)

    Ragulskene, V. L.

    1973-01-01

    Free vibrations of a system and vibrations which are multiples of them in frequency are discussed. The corresponding periodic forced vibrations of the type n/m (n is the number of periods of disturbance between periods of movement and m is the number of periods of movement in one period of disturbance), generated by a harmonic or close to harmonic disturbance, are propagated close to the corresponding curves of the free vibrations and their frequency multiples. It has been proposed that investigation of transitional modes of motion and capture regions be carried out by precise methods in phase space, with the least number of coordinates. Thus, for example, for nonautonomous second order equations (for example, the Duffing equations), in place of three variables (coordinates, velocity, phases), it is proposed to use two: velocity during transition of the coordinate through zero and phase.

  13. Molecular structures and vibrations of m-methylaniline in the S0 and S1 states studied by laser induced fluorescence spectroscopy and ab initio calculations.

    PubMed

    Santos, L; Martínez, E; Ballesteros, B; Sanchez, J

    2000-09-01

    The UV fluorescence excitation and dispersed fluorescence spectra of a jet-cooled m-methylaniline have been obtained for the S1<--S0 transition, in which some of the bands have been observed for the first time. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes. It was found that the spectra exhibit an important feature which is the internal rotation of the methyl group in the electronic ground and excited states. Ab initio calculations at MP2/6-31G* and CIS/6-31G* show that the optimized structure of m-methylaniline in the ground state is not planar with the amino group having sp3 hybridation-like character due to the existence of lone-paired electrons on the nitrogen atom. Upon electronic excitation, the C-N bond exhibits a partial double bond character, indicating an enhanced interaction between the ring and the NH2 group as in the case of aniline. PMID:10989882

  14. Asynchronous vibration problem of centrifugal compressor

    NASA Technical Reports Server (NTRS)

    Fujikawa, T.; Ishiguro, N.; Ito, M.

    1980-01-01

    An unstable asynchronous vibration problem in a high pressure centrifugal compressor and the remedial actions against it are described. Asynchronous vibration of the compressor took place when the discharge pressure (Pd) was increased, after the rotor was already at full speed. The typical spectral data of the shaft vibration indicate that as the pressure Pd increases, pre-unstable vibration appears and becomes larger, and large unstable asynchronous vibration occurs suddenly (Pd = 5.49MPa). A computer program was used which calculated the logarithmic decrement and the damped natural frequency of the rotor bearing systems. The analysis of the log-decrement is concluded to be effective in preventing unstable vibration in both the design stage and remedial actions.

  15. How do nuclei really vibrate or rotate

    SciTech Connect

    Andresen, H.G.; Kunz, J.; Mosel, U.; Mueller, M.; Schuh, A.; Wust, U.

    1983-01-01

    By means of the adiabatic cranking model the properties of the current and velocity fields of nuclear quadrupole vibrations for even-even nuclei in the rare-earth region are investigated. BCS correlated wave functions based on the Nilsson single particle Hamiltonian have been used. The current fields are analyzed in terms of vector spherical harmonics. The realistic microscopic currents show a vortex structure not present in the classical irrotational flow. The microscopic origin of the vortex structure is investigated.

  16. Simplified Analysis Of Vehicle/Payload Vibrations

    NASA Technical Reports Server (NTRS)

    Yu, Reginald R. J.

    1988-01-01

    Simplified mathematical model of coupled vibrations of vehicle and its payloads used in stability analysis for control purposes. Multiple-payload stability criterion extension of single-payload criterion based on measurements and detailed calculations of fundamental vibrational modes of vehicle and payload. Represented in simplified form by coupled masses and springs vibrating in one dimension, each spring having stiffness that gives rise to previously determined fundamental vibrational frequency associated mass in absence of coupling with other mass. Developed to avoid complexity and cost of full vibrations/stability calculations for each different combination of Space Shuttle payloads, simplified analysis technique also useful in assessing stability in loaded airplanes, ships, trucks, cranes, and conveyor systems.

  17. Deriving Strain Modes From Vibrational Tests

    NASA Technical Reports Server (NTRS)

    Young, J. W.; Joanides, J. C.

    1985-01-01

    Measurements and theoretical analysis complement each other. Experimental acceleration and strain data used to calculate coefficients of low-frequency vibrational modes of object under test. An iterative comparison of experimental and calculated strains give modal model of improved accuracy that predicts strains under operating conditions. Method useful in fatigue life and reliability analyses of buildings, pumps, engines, vehicles, and other systems subject to vibrations and loud noises during operation.

  18. Downhole vibration sensing by vibration energy harvesting

    E-print Network

    Trimble, A. Zachary

    2007-01-01

    This thesis outlines the design of a prototype electromagnetic induction vibration energy harvesting device for use in a downhole environment. First order models of the necessary components for a generic vibration energy ...

  19. A vibrational molecular force field of model compounds with biological interest. VII. Harmonic dynamics of N-acetyl-?- D-muramic acid and N-acetyl-?- D-neuraminic acid in the crystalline state

    NASA Astrophysics Data System (ADS)

    Kouach-Alix, I.; Huvenne, J. P.; Legrand, P.; Vergoten, G.

    1994-10-01

    Combining a modified Urey—Bradley—Shimanouchi intramolecular potential energy function with an appropriate intermolecular energy function, normal coordinate calculations have been performed for N-acetyl-?- D-muramic acid and for N-acetyl-?- D-neuraminic acid in the crystalline state. IR and Raman spectra were recorded. Overall agreement between the observed and the calculated frequencies leads to an average error of 4 cm -1. The computed potential energy distribution was found to be compatible with previous assignments for N-acetyl-?- D-glucoasamine for the pyranose ring and the acetamido group, and for pivalic acid for the carboxylic group. The sets of force constants used for the two monosaccharides were taken from previous works on monosaccharides.

  20. Harmonic leakage and image quality degradation in tissue harmonic imaging

    Microsoft Academic Search

    Che-Chou Shen; Pai-Chi Li

    2001-01-01

    Image quality degradation caused by harmonic leakage was studied for finite amplitude distortion-based harmonic imaging. Various sources of harmonic leakage, including transmit waveform, signal bandwidth, and system nonlinearity, were investigated using both simulations and hydrophone measurements. Effects of harmonic leakage in the presence of sound velocity inhomogeneities were also considered. Results indicated that sidelobe levels of the harmonic beam pattern

  1. Lab 5: Damped simple harmonic motion Simple harmonic oscillation

    E-print Network

    Glashausser, Charles

    Lab 5: Damped simple harmonic motion · Simple harmonic oscillation · Damped harmonic oscillation;Friction: retarding motion (energy dissipation) Damped simple harmonic oscillation 1 2 Hooke's law: Damping 381 Mechanics #12;Ideal case: no friction Simple harmonic oscillation Hooke's law: Newton's 2nd law: F

  2. Harmonic analysis in a power system with wind generation

    Microsoft Academic Search

    Stavros A. Papathanassiou; Michael P. Papadopoulos

    2006-01-01

    Variable-speed wind turbines inject harmonic currents in the network, which may potentially create voltage distortion problems. In this paper, a case study is presented for a 10-MW wind farm, intended to be connected to a network with extended high-voltage submarine cable lines. First, the system modeling approach and the harmonic load-flow calculation is described. Then, the harmonic impedance of the

  3. Relativistic harmonic content of nonlinear electromagnetic waves in underdense plasmas

    Microsoft Academic Search

    W. B. Mori; C. D. Decker; W. P. Leemans

    1993-01-01

    The relativistic harmonic content of large-amplitude electromagnetic waves propagating in underdense plasmas is investigated. The steady-state harmonic content of nonlinear linearly polarized waves is calculated for both the very underdense (wp\\/w 0)≪1 and critical density (wp\\/w0)≃1 limits. For weak nonlinearities, eE0\\/mc?0<1, the nonlinear source term for the third harmonic is derived for arbitrary wp\\/w0. Arguments are given for extending these

  4. Separation of High Order Harmonics with Fluoride Windows

    SciTech Connect

    Allison, Tom; van Tilborg, Jeroen; Wright, Travis; Hertlein, Marcus; Falcone, Roger; Belkacem, Ali

    2010-08-02

    The lower orders produced in high order harmonic generation can be effciently temporally separated into monochromatic pulses by propagation in a Fluoride window while still preserving their femtosecond pulse duration. We present calculations for MgF2, CaF2, and LiF windows for the third, fifth, and seventh harmonics of 800 nm. We demonstrate the use of this simple and inexpensive technique in a femtosecond pump/probe experiment using the fifth harmonic.

  5. Vibrational line shapes of solvated molecules with a normal mode approach

    Microsoft Academic Search

    Stephen J. Schvaneveldt; Roger F. Loring

    1995-01-01

    We develop a theory of the vibrational absorption line shape of a solvated molecule. This approach is based on the instantaneous normal mode approximation, in which the fluid is taken to evolve on a harmonic potential surface whose curvature matches that of the true potential surface at the fluid’s initial configuration. We apply this method to the vibrational line shape

  6. Even harmonic lasing

    SciTech Connect

    Schmitt, M.J.

    1991-01-01

    Operation of a free-electron laser at harmonics of the fundamental frequency is explored with the numerical simulation code HELEX. This code includes coupling to the harmonics caused by misalignment of the electrons with the optical beam and coupling due to transverse gradients. Albeit weak, the transverse gradients produce the dominant coupling of the electrons to the even-harmonic light. Even-harmonic lasing occurs in a TEM{sub 0,2m+1}-like mode where the field on axis is zero. As bunching of the electron beam progresses, radiation at the higher odd harmonics is suppressed owing to the absence of higher-order odd-harmonic Fourier components in the bunch. Growth of the even-harmonic power from small signal requires suppression of competing harmonics (including the fundamental) that have higher gain. Lasing at an even harmonic has yet to be experimentally demonstrated in an open resonator (i.e. optical cavity). Strategies to make such an experiment possible are discussed. 9 refs., 5 figs., 1 tab.

  7. Quantum chemical approach for condensed-phase thermochemistry: Proposal of a harmonic solvation model

    NASA Astrophysics Data System (ADS)

    Nakai, Hiromi; Ishikawa, Atsushi

    2014-11-01

    We propose a novel quantum chemical method, called the harmonic solvation model (HSM), for calculating thermochemical parameters in the condensed phase, particularly in the liquid phase. The HSM represents translational and rotational motions of a solute as vibrations interacting with a cavity wall of solvent molecules. As examples, the HSM and the ideal-gas model (IGM) were used for the standard formation reaction of liquid water, combustion reactions of liquid formic acid, methanol, and ethanol, vapor-liquid equilibration of water and ethanol, and dissolution of gaseous CO2 in water. The numerical results confirmed the reliability and applicability of the HSM. In particular, the temperature dependence of the Gibbs energy of liquid molecules was accurately reproduced by the HSM; for example, the boiling point of water was reasonably determined using the HSM, whereas the conventional IGM treatment failed to obtain a crossing of the two Gibbs energy curves for gaseous and liquid water.

  8. Quantum chemical approach for condensed-phase thermochemistry: proposal of a harmonic solvation model.

    PubMed

    Nakai, Hiromi; Ishikawa, Atsushi

    2014-11-01

    We propose a novel quantum chemical method, called the harmonic solvation model (HSM), for calculating thermochemical parameters in the condensed phase, particularly in the liquid phase. The HSM represents translational and rotational motions of a solute as vibrations interacting with a cavity wall of solvent molecules. As examples, the HSM and the ideal-gas model (IGM) were used for the standard formation reaction of liquid water, combustion reactions of liquid formic acid, methanol, and ethanol, vapor-liquid equilibration of water and ethanol, and dissolution of gaseous CO2 in water. The numerical results confirmed the reliability and applicability of the HSM. In particular, the temperature dependence of the Gibbs energy of liquid molecules was accurately reproduced by the HSM; for example, the boiling point of water was reasonably determined using the HSM, whereas the conventional IGM treatment failed to obtain a crossing of the two Gibbs energy curves for gaseous and liquid water. PMID:25381501

  9. Quantum chemical approach for condensed-phase thermochemistry: Proposal of a harmonic solvation model

    SciTech Connect

    Nakai, Hiromi, E-mail: nakai@waseda.jp [Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); ESICB, Kyoto University, Kyotodaigaku-Katsura, Kyoto 615-8520 (Japan); Ishikawa, Atsushi [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); ESICB, Kyoto University, Kyotodaigaku-Katsura, Kyoto 615-8520 (Japan)

    2014-11-07

    We propose a novel quantum chemical method, called the harmonic solvation model (HSM), for calculating thermochemical parameters in the condensed phase, particularly in the liquid phase. The HSM represents translational and rotational motions of a solute as vibrations interacting with a cavity wall of solvent molecules. As examples, the HSM and the ideal-gas model (IGM) were used for the standard formation reaction of liquid water, combustion reactions of liquid formic acid, methanol, and ethanol, vapor–liquid equilibration of water and ethanol, and dissolution of gaseous CO{sub 2} in water. The numerical results confirmed the reliability and applicability of the HSM. In particular, the temperature dependence of the Gibbs energy of liquid molecules was accurately reproduced by the HSM; for example, the boiling point of water was reasonably determined using the HSM, whereas the conventional IGM treatment failed to obtain a crossing of the two Gibbs energy curves for gaseous and liquid water.

  10. Active vibration and noise alleviation in rotorcraft using microflaps

    NASA Astrophysics Data System (ADS)

    Padthe, Ashwani Kumar

    This work presents a comprehensive analysis of active Gurney flaps, or microflaps, for on blade control of noise and vibration in rotorcraft. The initial portion of the work considered the two-dimensional unsteady aerodynamic characteristics of three different oscillating microflap configurations using a compressible computational fluid dynamics (CFD) flow solver. Among these the configuration most suitable for rotorcraft applications was chosen. An unsteady reduced order aerodynamic model (ROM) was developed for the microflap using the Rational Function Approximation approach and CFD based oscillatory aerodynamic load data. The resulting ROM is a state-space, time-domain model that accounts for unsteadiness, compressibility and time-varying freestream effects. The ROM was validated against direct CFD calculations for a wide range of flow conditions showing excellent agreement. Subsequently, the ROM was then incorporated into a comprehensive rotorcraft simulation code featuring a free-wake model, an acoustic prediction tool, and fully coupled flap-lag-torsional blade dynamics. The higher harmonic control (HHC) algorithm was used to simulate closed-loop active control with a 1.5% chord microflap on a hingeless rotor configuration resembling the MBB BO-105. Three span-wise configurations, single, dual, and a five-microflap configuration were considered. Results indicate that the microflap can achieve reductions ranging from 3-6 dB in the blade-vortex interaction (BVI) noise. Vibration reduction ranging from 70-90% was also demonstrated at both low-speed and high-speed flight conditions. It was also found that reduction in BVI noise results in an increase in vibrations and vice versa, a trend also noted in previous active control studies employing HHC and conventional partial span trailing-edge flaps. Next, simultaneous BVI noise and vibration reduction was studied. A reduction of 2-3 dB in the advancing and retreating side noise combined with a 55% reduction in the vibratory loads was achieved using the five-microflap configuration. The 1.5% chord microflap was also compared to a 20% chord plain trailing-edge flap showing similar effectiveness in reducing vibration and noise. Finally, a new approach for dealing with actuator saturation in the HHC algorithm was developed using nonlinear constrained optimization techniques. The optimization approach takes less computational time compared to the previous approaches while yielding better performance in the case of multiple control surfaces.

  11. Vibrational spectral investigation, NBO, first hyperpolarizability and UV-Vis spectral analysis of 3,5-dichlorobenzonitrile and m-bromobenzonitrile by ab initio and density functional theory methods

    NASA Astrophysics Data System (ADS)

    Senthil kumar, J.; Jeyavijayan, S.; Arivazhagan, M.

    2015-02-01

    The FT-IR and FT-Raman spectra of 3,5-dichlorobenzonitrile and m-bromobenzonitrile have been recorded in the region 4000-400 cm-1 and 3500-50 cm-1, respectively. The optimized geometry, wave numbers and intensity of vibrational bonds of title molecules are obtained by ab initio and DFT level of theory with complete relaxation in the potential energy surface using 6-311++G(d, p) basis set. A complete vibrational assignments aided by the theoretical harmonic frequency, analysis have been proposed. The harmonic vibrational frequencies calculated have been compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The UV-Vis spectral analysis of the molecules has also been done which confirms the charge transfer of the molecules. Furthermore, the first hyperpolarizability and total dipole moment of the molecules have been calculated.

  12. Full dimensional Franck-Condon factors for the acetylene A? (1)Au-X? (1)?(g)(+) transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes.

    PubMed

    Park, G Barratt; Baraban, Joshua H; Field, Robert W

    2014-10-01

    A full-dimensional Franck-Condon calculation has been applied to the A? (1)Au-X? 1?g+ transition in acetylene in the harmonic normal mode basis. Details of the calculation are discussed in Part I of this series. To our knowledge, this is the first full-dimensional Franck-Condon calculation on a tetra-atomic molecule undergoing a linear-to-bent geometry change. In the current work, the vibrational intensity factors for levels involving excitation in ungerade vibrational modes are evaluated. Because the Franck-Condon integral accumulates away from the linear geometry, we have been able to treat the out-of-plane component of trans bend (?4('')) in the linear X? state in the rotational part of the problem, restoring the ? Euler angle and the a-axis Eckart conditions. A consequence of the Eckart conditions is that the out-of-plane component of ?4('') does not participate in the vibrational overlap integral. This affects the structure of the coordinate transformation and the symmetry of the vibrational wavefunctions used in the overlap integral, and results in propensity rules involving the bending modes of the X? state that were not previously understood. We explain the origin of some of the unexpected propensities observed in IR-UV laser-induced fluorescence spectra, and we calculate emission intensities from bending levels of the A? state into bending levels of the X? state, using normal bending mode and local bending mode basis sets. Our calculations also reveal Franck-Condon propensities for the Cartesian components of the cis bend (?5('')), and we predict that the best A?-state vibrational levels for populating X?-state levels with large amplitude bending motion localized in a single C-H bond (the acetylene?vinylidene isomerization coordinate) involve a high degree of excitation in ?6(') (cis-bend). Mode ?4(') (torsion) populates levels with large amplitude counter-rotational motion of the two hydrogen atoms. PMID:25296804

  13. Vibrational spectrum of buspirone

    NASA Astrophysics Data System (ADS)

    Cybulski, Jacek; Chilmonczyk, Zdzis?aw; Glice, Magdalena; Cybulski, Marcin; Bajdor, Krzysztof; Le?, Andrzej

    1997-02-01

    The IR and Raman spectra of buspirone and buspirone hydrochloride were recorded in KBr pellets and chloroform solutions. Most of the vibrational bands were assigned to normal modes using quantum mechanical semiempirical and ab initio restricted Hartree-Fock (RHF) calculations on model systems. The essential spectral characteristics can be obtained from the analysis of three building blocks of buspirone, i.e. pyrimidine-piperazine, butyl spacer and imide residues. The spectral regions particularly sensitive to intermolecular interactions were identified. The theoretical calculations suggest that the "NH +" band in buspirone hydrochloride reflects the formation of a moderately strong hydrogen bond between the protonated piperazine nitrogen atom (bound to the butyl spacer) and the chlorine anion.

  14. Dual Time Stepping Algorithms With the High Order Harmonic Balance Method for Contact Interfaces With Fretting-Wear

    E-print Network

    Salles, Loic; Gouskov, Alexandre; Jean, Pierrick; Thouverez, Fabrice

    2014-01-01

    Contact interfaces with dry friction are frequently used in turbomachinery. Dry friction damping produced by the sliding surfaces of these interfaces reduces the amplitude of bladed-disk vibration. The relative displacements at these interfaces lead to fretting-wear which reduces the average life expectancy of the structure. Frequency response functions are calculated numerically by using the multi-harmonic balance method (mHBM). The dynamic Lagrangian frequency-time method is used to calculate contact forces in the frequency domain. A new strategy for solving nonlinear systems based on dual time stepping is applied. This method is faster than using Newton solvers. It was used successfully for solving Nonlinear CFD equations in the frequency domain. This new approach allows identifying the steady state of worn systems by integrating wear rate equations a on dual time scale. The dual time equations are integrated by an implicit scheme. Of the different orders tested, the first order scheme provided the best re...

  15. calculators hp calculators

    E-print Network

    Vetter, Frederick J.

    calculators hp calculators HP 50g Calculations involving plots Plotting on the HP 50g The 2D/3D;hp calculators HP 50g Calculations involving plots hp calculators - 2 - HP 50g Calculations involving plots Plotting on the HP 50g The HP 50g calculator provides a host of plots to allow the user

  16. HARMONIC FUNCTIONS WITH POLYNOMIAL GROWTH

    E-print Network

    Minicozzi, William

    HARMONIC FUNCTIONS WITH POLYNOMIAL GROWTH TOBIAS 1 1. Harmonic functions with polynomial growth on cones 5 2. Tools to study the growth of harmonic functions on manifolds 13 3. Lower bound of the frequency

  17. Molecular dynamics modeling of the sub-THz vibrational absorption of thioredoxin from E. coli.

    PubMed

    Alijabbari, Naser; Chen, Yikan; Sizov, Igor; Globus, Tatiana; Gelmont, Boris

    2012-05-01

    Sub-terahertz (THz) vibrational modes of the protein thioredoxin in a water environment were simulated using molecular dynamics (MD) in order to find the conditions needed for simulation convergence, improve the correlation between experimental and simulated absorption frequencies, and ultimately enhance the predictive capabilities of computational modeling. Thioredoxin from E. coli was used as a model molecule for protocol development and to optimize the simulation parameters. The empirically parameterized software packages Amber 8 and 10 were used in this work. Using atomic trajectories from the constant energy and volume MD simulations, thioredoxin's sub-THz vibrational spectra and absorption coefficients were calculated in a quasi-harmonic approximation. An optimal production run length ~100 ps was found, in agreement with experimental data on thioredoxin relaxation dynamics. At the same time, a new procedure was developed for averaging correlation matrices of atomic coordinates in MD simulations. In particular, the open source package ptraj was edited to improve a matrix-analyzing function. Averaging only six matrices gave much more consistent results, with absorption peak intensities exceeding those from the individual spectra and a rather good correlation between simulated vibrational frequencies and experimental data. PMID:21947449

  18. Geometrically nonlinear free vibrations of simply supported isotropic thin circular plates

    NASA Astrophysics Data System (ADS)

    Haterbouch, M.; Benamar, R.

    2005-02-01

    Nonlinear free axisymmetric vibration of simply supported isotropic circular plates is investigated by using the energy method and a multimode approach. In-plane deformation is included in the formulation. Lagrange's equations are used to derive the governing equation of motion. Using the harmonic balance method, the equation of motion is converted into a nonlinear algebraic form. The numerical iterative method of solution adopted here is the so-called linearized updated mode method, which permits the authors to obtain accurate results for vibration amplitudes up to three times the plate thickness. The percentage of participation of each out-of-plane basic function to the deflection shape and to the bending stress at the plate centre and of each in-plane basic function to the membrane stress at the centre are calculated in order to determine the minimum number of in- and out-of-plane basic functions to be used in order to achieve a good accuracy of the model. The nonlinear frequency, the nonlinear fundamental mode shape and their associated nonlinear bending and membrane stresses are determined at large amplitudes of vibration. The numerical results obtained here are presented and compared with available published results, based on various approaches and with the single-mode solution. The limit of validity of the single-mode approach is also investigated.

  19. Vibrational study of intramolecular hydrogen bonding in o-hydroxybenzoyl compounds

    NASA Astrophysics Data System (ADS)

    Palomar, J.; De Paz, J. L. G.; Catalán, J.

    1999-07-01

    The vibrational study of a set of o-hydroxybenzoyl compounds (salicylaldehyde, o-hydroxyacetophenone, methyl salicylate and salicylamide) and their parent compounds (phenol, benzaldehyde, acetophenone, methyl benzoate and benzamide) has been performed by infrared (IR) measurements and by quantum chemical calculations using B3LYP density functional in conjunction with 6-31G ?? and 6-311++G(3df, 2p) basis sets. The assignment of the infrared bands results unequivocal for most cases, including those signals in which the motion of the intramolecular hydrogen bond (IMHB) is involved. The analysis of the IR spectra for the deuterated derivatives was proved to be a very useful tool for this purpose. A model based on isotopically substituted benzenes was used for classifying the phenyl ring movements of the molecules studied. The results obtained show the suitability and limitation of the harmonic treatment using B3LYP method to describe the characteristic IMHB vibrations. Vibrational data are analyzed in order to obtain information about the nature of the hydrogen bonding interaction in this family of compounds. Finally, the available empirical relationships to approximate the IMHB energy from experimental spectroscopic data are revised in view of the new theoretical results.

  20. [Study on the spectroscopic data and vibrational levels of the ground SiH+ molecular ion].

    PubMed

    Zhao, Jun; Zeng, Hui

    2014-12-01

    The ground electronic state and the reasonable dissociation limit of SiH+ molecular ion have been correctly determined based on group theory and atomic and molecular reaction statics. The energy, equilibrium geometry and harmonic frequency of the ground electronic state of SiH+ molecular ion have been calculated using the method QCISD(T)/cc-pVQZ. The whole potential curves for the ground electronic state is further scanned using the above method, the potential energy functions and relevant spectroscopic constants of this state are then first obtained by least square fitting to the Murrell-Sorbie function (n=9) and the modified Murrell-Sorbie+c6 function, respectively. The present results showed that the calculated results based on the Murrell-Sorbie function (n=9) are in better agreement with the experimental values, with the relative errors between spectroscopic constants and the experimental values being 0.13%, 3.07%, 0.38%, 5.25% and 0.52% respectively. With the potential obtained at the QCISD(T)/cc-pVQZ level of theory, the total of 27 vibrational states are predicted when J=0 by numerically solving the radial Schrodinger equation of nuclear motion. The complete vibrational levels, inertial rotation and six centrifugal distortion constants are obtained for the ground electronic state of SiH+ molecular ion for the first time. Calculation results in the present work may provide theoretical supports for the further study of SiH+ molecular ion. PMID:25881406

  1. On Mechanical Modeling of Cantilevered Piezoelectric Vibration Energy Harvesters

    Microsoft Academic Search

    A. Erturk; D. J. Inman

    2008-01-01

    Cantilevered beams with piezoceramic (PZT) layers are the most commonly investigated type of vibration energy harvesters. A frequently used modeling approach is the single-degree-of-freedom (SDOF) modeling of the harvester beam as it allows simple expressions for the electrical outputs. In the literature, since the base excitation on the harvester beam is assumed to be harmonic, the well known SDOF relation

  2. Ab-initio calculations and phase diagram assessments of An-Al systems (An = U, Np, Pu)

    NASA Astrophysics Data System (ADS)

    Sedmidubský, D.; Konings, R. J. M.; Sou?ek, P.

    2010-02-01

    The enthalpies of formation of binary intermetallic compounds AnAl n(n=2,3,4, An=U,Np,Pu) were assessed from first principle calculations of total energies performed using full potential APW + lo technique within density functional theory ( WIEN2k). The substantial contribution to entropies, S298°, arising from lattice vibrations was calculated by direct method within harmonic crystal approximation ( Phonon software + VASP for obtaining Hellmann-Feynman forces). The electronic heat capacity and the corresponding contribution to entropy were estimated from the density of states at Fermi level obtained from electronic structure calculations. The phase diagrams of the relevant systems An-Al were calculated based on the thermodynamic data assessed from ab-initio calculations, known equilibrium and calorimetry data by employing the FactSage program.

  3. Harmonic analysis of spacecraft power systems using a personal computer

    NASA Technical Reports Server (NTRS)

    Williamson, Frank; Sheble, Gerald B.

    1989-01-01

    The effects that nonlinear devices such as ac/dc converters, HVDC transmission links, and motor drives have on spacecraft power systems are discussed. The nonsinusoidal currents, along with the corresponding voltages, are calculated by a harmonic power flow which decouples and solves for each harmonic component individually using an iterative Newton-Raphson algorithm. The sparsity of the harmonic equations and the overall Jacobian matrix is used to an advantage in terms of saving computer memory space and in terms of reducing computation time. The algorithm could also be modified to analyze each harmonic separately instead of all at the same time.

  4. Molecular structure, intramolecular hydrogen bonding and vibrational spectral investigation of 2-fluoro benzamide--a DFT approach.

    PubMed

    Krishnakumar, V; Murugeswari, K; Surumbarkuzhali, N

    2013-10-01

    The FTIR and FT-Raman spectra of 2-fluoro benzamide (2FBA) have been recorded in the region 4000-400 and 4000-100 cm(-1), respectively. The structuralanalysis, hydrogen bonding, optimized geometry, frequency and intensity of the vibrational bands of 2FBA were obtained by the density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G** basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The (13)C NMR spectra have been recorded and (13)C nuclear magnetic resonance chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method and their respective linear correlations were obtained. The electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The Mulliken charges, the values of electric dipole moment (?) of the molecule were computed using DFT calculations. The change in electron density (ED) in the ?* antibonding orbitals and stabilization energies E(2) have been calculated by natural bond (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interactions. PMID:23792236

  5. Intermolecular bonding and vibrations of phenol?H2O (D2O)

    NASA Astrophysics Data System (ADS)

    Schütz, Martin; Bürgi, Thomas; Leutwyler, Samuel; Fischer, Thomas

    1993-03-01

    Extensive ab initio calculations of the phenol?H2O complex were performed at the Hartree-Fock level, using the 6-31G(d,p) and 6-311++G(d,p) basis sets. Fully energy-minimized geometries were obtained for (a) the equilibrium structure, which has a translinear H bond and the H2O plane orthogonal to the phenol plane, similar to (H2O)2; (b) the lowest-energy transition state structure, which is nonplanar (C1 symmetry) and has the H2O moiety rotated by ±90°. The calculated MP2/6-311G++(d,p) binding energy including basis set superposition error corrections is 6.08 kcal/mol; the barrier for internal rotation around the H bond is only 0.4 kcal/mol. Intra- and intermolecular harmonic vibrational frequencies were calculated for a number of different isotopomers of phenol?H2O. Anharmonic intermolecular vibrational frequencies were computed for several intermolecular vibrations; anharmonic corrections are very large for the ?2 intermolecular wag. Furthermore, the H2O torsion ? around the H-bond axis, and the ?2 mode are strongly anharmonically coupled, and a two-dimensional ?/?2 potential energy surface was explored. The role of tunneling splitting due to the torsional mode is discussed and tunnel splittings are estimated for the calculated range of barriers. The theoretical studies were complemented by a detailed spectroscopic study of h-phenol?H2O and d-phenol?D2O employing two-color resonance-two-photon ionization and dispersed fluorescence emission techniques, which extends earlier spectroscopic studies of this system. The ?1 and ?2 wags of both isotopomers in the S0 and S1 electronic states are newly assigned, as well as several other weaker transitions. Tunneling splittings due to the torsional mode may be important in the S0 state in conjunction with the excitation of the intermolecular ? and ?2 modes.

  6. Making space for harmonic oscillators

    SciTech Connect

    Michelotti, Leo; /Fermilab

    2004-11-01

    If we restrict the number of harmonic oscillator energy eigenstates to some finite value, N, then the discrete spectrum of the corresponding position operator comprise the roots of the Hermite polynomial H{sub N+1}. Its range is just large enough to accommodate classical motion at high energy. A negative energy term must be added to the Hamiltonian which affects only the last eigenstate, |N>, suggesting it is concentrated at the extrema of this finite ''space''. Calculations support a conjecture that, in the limit of large N, the global distribution of points approaches the differential form for classical action.

  7. Model parameters of the nonlinear stiffness of the vibrator-ground contact determined by inversion of vibrator accelerometer data

    E-print Network

    Beresnev, Igor

    Model parameters of the nonlinear stiffness of the vibrator-ground contact determined by inversion and the comparison of predicted and observed harmonic levels. The inverse problem was solved for models of bilin- ear/m in tension were resolved from the inversion for both models, although the smooth nonlinear-rigidity model

  8. Quantum harmonic oscillator state synthesis and analysis

    E-print Network

    W. M. Itano; C. Monroe; D. M. Meekhof; D. Leibfried; B. E. King; D. J. Wineland

    1997-02-19

    Experiments are described in which a single, harmonically bound, beryllium ion in a Paul trap is put into Fock, thermal, coherent, squeezed, and Schroedinger cat states. Experimental determinations of the density matrix and the Wigner function are described. A simple calculation of the decoherence of a superposition of coherent states due to an external electric field is given.

  9. Evidences of the formation of a tin(IV) complex in citric-citrate buffer solution: A study based on voltammetric, FTIR and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Bichara, Laura Cecilia; Fiori Bimbi, María Victoria; Gervasi, Claudio Alfredo; Alvarez, Patricia Eugenia; Brandán, Silvia Antonia

    2012-01-01

    We studied the Sn(IV)-complex, [Sn(C 6H 4O 7) 2] 2- formed after anodic dissolution of a tin surface through its passive oxide film in citric-citrate aqueous solution buffer pH 3. Tin-complex was experimentally characterized using infrared spectroscopy while ab initio calculations were made to study its structure and vibrational properties. These calculations gave us a precise knowledge of the normal modes of vibration taking into account that in the complex the molecule comprises a system of two citrate ions that are attached to a central Sn(IV) atom. The coordination about Sn(IV) consists of a distorted octahedral SnO 6 where two tridentate citrates are bonding to the central metal. The calculated harmonic vibrational frequencies are consistent with the experimental vibrational spectra. The theoretical calculations of the wavenumbers allowed us to obtain a tentative assignment of the observed spectral features. The nature of the different Sn-O and Sn ? O bonds in the complex and their topological properties were investigated by means of natural bond orbital (NBO) analysis and Bader's atoms in the molecule (AIM) theory, respectively.

  10. Structural and vibrational spectroscopic studies on charge transfer and ionic hydrogen bonding interactions of melaminium benzoate dihydrate

    NASA Astrophysics Data System (ADS)

    Kanagathara, N.; Marchewka, M. K.; Drozd, M.; Gunasekaran, S.; Rajakumar, P. R.; Anbalagan, G.

    2015-06-01

    Single crystals of melaminium benzoate dihydrate (MBDH) have been grown from aqueous solution by the slow solvent evaporation method at room temperature. Crystalline nature of the grown crystal has been confirmed by X-ray powder diffraction studies. The optimized geometry, frequency and intensity of the vibrational bands of MBDH were obtained by the Hartree-Fock and density functional theory using B3LYP/cam-B3LYP with 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with the experimental FT-IR and FT-Raman spectral values. The obtained vibrational wavenumbers and optimized geometric parameters are found to be in good agreement with the experimental data. UV-Visible spectrum was recorded in the region 200-400 nm and the electronic properties, HOMO-LUMO energies and other related electronic parameters are calculated. The isotropic chemical shifts computed by 1H and 13C NMR analysis also show good agreement with experimental observation. Natural bond orbital (NBO) analysis has been performed on MBDH compound to analyze the stability of the molecule arising from hyperconjugative interactions and charge delocalization. Molecular electrostatic potential surface (MEP) has also been performed by DFT/cam-B3LYP method with 6-311++G(d,p) basis set. Differential scanning calorimetric measurements performed on the powder sample indicate the phase transition point approximately at 368 and 358 K for heating and cooling, respectively.

  11. Experimental (FTIR and FT-Raman) and ab initio and DFT study of vibrational frequencies of 5-amino-2-nitrobenzoic acid.

    PubMed

    Ramalingam, M; Sundaraganesan, N; Saleem, H; Swaminathan, J

    2008-11-01

    The FTIR and FT-Raman spectra of 5-amino-2-nitrobenzoic acid (ANB) have been recorded in the region 400-4000 cm(-1). The observed frequencies were assigned to different modes of vibrations on the basis of fundamental, combination and overtones. The geometry has been optimized with complete relaxation on the potential energy surface at HF, MP2 and B3LYP level of theories using 6-311++G(d,p) basis set and compared with the crystal data. The possible hydrogen bond interaction has been estimated taking a model compound. Further harmonic vibrational frequency calculations have been carried out at HF and B3LYP levels and the scaled values were in good agreement with majority of the experimental observations. The theoretically constructed spectra coincide satisfactorily with those of experimental spectra. PMID:18178128

  12. Transformation of spherical harmonic coefficients to ellipsoidal harmonic coefficients

    Microsoft Academic Search

    D. Dechambre; D. J. Scheeres

    2002-01-01

    Analytical expressions linking spherical harmonics gravity field expansions with ellipsoidal harmonics gravity field expansions are developed. Certain symmetries and simplifications for the transformation between the two are noted. Using the expressions, a numerical approach is developed and applied for the computation of ellipsoidal harmonic gravity coefficients using spherical harmonics coefficients as inputs. This method can be used to transform a

  13. Transformation of spherical harmonic coecients to ellipsoidal harmonic coecients

    Microsoft Academic Search

    D. Dechambre; D. J. Scheeres

    2002-01-01

    Analytical expressions linking spherical harmonics gravity eld expansions with ellipsoidal harmonics gravity eld expansions are developed. Certain symmetries and simplications for the transformation between the two are noted. Using the expressions, a numerical approach is developed and applied for the computation of ellipsoidal harmonic gravity coecients using spherical harmonics coecients as inputs. This method can be used to transform a

  14. Vibrational neutron spectroscopy of collagen and model polypeptides.

    PubMed Central

    Middendorf, H D; Hayward, R L; Parker, S F; Bradshaw, J; Miller, A

    1995-01-01

    A pulsed source neutron spectrometer has been used to measure vibrational spectra (20-4000 cm-1) of dry and hydrated type I collagen fibers, and of two model polypeptides, polyproline II and (prolyl-prolyl-glycine)10, at temperatures of 30 and 120 K. the collagen spectra provide the first high resolution neutron views of the proton-dominated modes of a protein over a wide energy range from the low frequency phonon region to the rich spectrum of localized high frequency modes. Several bands show a level of fine structure approaching that of optical data. The principal features of the spectra are assigned. A difference spectrum is obtained for protein associated water, which displays an acoustic peak similar to pure ice and a librational band shifted to lower frequency by the influence of the protein. Hydrogen-weighted densities of states are extracted for collagen and the model polypeptides, and compared with published calculations. Proton mean-square displacements are calculated from Debye-Waller factors measured in parallel quasi-elastic neutron-scattering experiments. Combined with the collagen density of states function, these yield an effective mass of 14.5 a.m.u. for the low frequency harmonic oscillators, indicating that the extended atom approximation, which simplifies analyses of low frequency protein dynamics, is appropriate. PMID:8527680

  15. Effect of the Vibrational Modes on the Ag-Cu Phase Diagram

    Microsoft Academic Search

    Su-Qing Duan; Xian-Geng Zhao; Shao-Jun Liu; Ben-Kun Ma

    2000-01-01

    We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrational free energies by using the method of ab initio inverted interatomic potentials and dynamic matrix; (2) the vibrational free energies determined by a Debye-Grüneisen approximation. The

  16. Multi-reference vibration correlation methods

    SciTech Connect

    Pfeiffer, Florian; Rauhut, Guntram, E-mail: rauhut@theochem.uni-stuttgart.de [Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany)] [Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany)

    2014-02-14

    State-specific vibration correlation methods beyond the vibrational multi-configuration self-consistent field (VMCSCF) approximation have been developed, which allow for the accurate calculation of state energies for systems suffering from strong anharmonic resonances. Both variational multi-reference configuration interaction approaches and an implementation of approximate 2nd order vibrational multi-reference perturbation theory are presented. The variational approach can be significantly accelerated by a configuration selection scheme, which leads to negligible deviations in the final results. Relaxation effects due to the partitioning of the correlation space and the performance of a VMCSCF modal basis in contrast to a standard modal basis obtained from vibrational self-consistent field theory have been investigated in detail. Benchmark calculations based on high-level potentials are provided for the propargyl cation and cis-diazene.

  17. Molecular structure, vibrational spectroscopic (FT-IR, FT-Raman), UV-vis spectra, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis, thermodynamic properties of benzophenone 2,4-dicarboxylic acid by ab initio HF and density functional method.

    PubMed

    Chaitanya, K

    2012-02-01

    The FT-IR (4000-450 cm(-1)) and FT-Raman spectra (3500-100 cm(-1)) of benzophenone 2,4-dicarboxylic acid (2,4-BDA) have been recorded in the condensed state. Density functional theory calculation with B3LYP/6-31G(d,p) basis set have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman activities and bonding features of the title compounds. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of 2,4-BDA is calculated using HF/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO analysis. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charges is also calculated. Because of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV-vis spectra and electronic absorption properties were explained and illustrated from the frontier molecular orbitals. PMID:22137747

  18. Molecular structure, vibrational spectroscopic (FT-IR, FT-Raman), UV-vis spectra, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis, thermodynamic properties of benzophenone 2,4-dicarboxylic acid by ab initio HF and density functional method

    NASA Astrophysics Data System (ADS)

    Chaitanya, K.

    2012-02-01

    The FT-IR (4000-450 cm -1) and FT-Raman spectra (3500-100 cm -1) of benzophenone 2,4-dicarboxylic acid (2,4-BDA) have been recorded in the condensed state. Density functional theory calculation with B3LYP/6-31G(d,p) basis set have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman activities and bonding features of the title compounds. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability ( ?0) and related properties ( ?, ?0 and ? ?) of 2,4-BDA is calculated using HF/6-31G(d,p) method on the finite-field approach. The stability of molecule has been analyzed by using NBO analysis. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. Mulliken population analysis on atomic charges is also calculated. Because of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated. Finally, the UV-vis spectra and electronic absorption properties were explained and illustrated from the frontier molecular orbitals.

  19. Surface Vibrations in a Model Hcp Crystal

    E-print Network

    Allen, Roland E.; Alldredg, GP; DEWITTE, FW.

    1972-01-01

    , and F. W. de Wette, Phys. Rev. B4, 1661 (1971). PHYSICA L RE VIE W 8 VOLUME 6, NUMBE R 2 15 JULY 1972 Surface Vibrations in a Model hcp Crystal R. E. Allen Department of Physics, Texas A @ M University, College Station, Texas 77843 and G. P.... Alldredge and F. %. de bette Department of Physics, University of Texas, Austin, Texas 78712 (Received 16 February 1972) The surface relaxation, vibrational modes, mean-square amplitudes of vibration, etc. , have been calculated for the (0001) surface...

  20. Lattice Vibrations and Superconductivity in Layered Structures

    E-print Network

    Allen, Roland E.; Alldredg, GP; WETTE, FWD.

    1970-01-01

    PHYSICAL REVIEW B VOLUME 2, NUMBER 7 1 OCTOB ER, 1970 Lattice Vibrations and Superconductivity in Layered Structures* B. E. Allen, G. P. Alldredge, and F. W. de bette DePartment of Physics, University of Texas, Austin, Texas 78712 (Received 18... May 1970) In order to estimate the influence of both surface and interface effects on phonon frequencies and superconducting transition temperatures in layered structures, we have calculated the vibrational modes of structures composed...

  1. NSLS II Vibration and Acoustic Criteria Vibration Experiment Hall

    E-print Network

    Ohta, Shigemi

    NSLS II Vibration and Acoustic Criteria Vibration ­ Experiment Hall The vibration limits at this time. It may only be possible to represent the vibration requirements of this space using generic vibration criteria. The vibration needs of the vast majority of research equipment available today would

  2. Solid state characterization of olanzapine polymorphs using vibrational spectroscopy.

    PubMed

    Ayala, A P; Siesler, H W; Boese, R; Hoffmann, G G; Polla, G I; Vega, D R

    2006-12-01

    FT-Raman, infrared and near infrared investigations of two polymorphs of olanzapine are presented, establishing the main features that allow the discrimination of these crystalline forms using vibrational spectroscopic methods. Ab initio calculations on the basis of the density functional theory were used to determine the stable conformations. The calculated vibrational spectra were compared to the experimental ones in order to identify the conformers corresponding to each polymorph and to assign the vibrational bands to the internal vibrations of the olanzapine molecule. Our results support the hydrogen bonding pattern proposed by the reported crystalline structure and provide valuable information on the structural and thermodynamical relationship between the investigated polymorphs. PMID:16949223

  3. The phase diagram of ice Ih, II, and III: A quasi-harmonic study

    NASA Astrophysics Data System (ADS)

    Ramírez, R.; Neuerburg, N.; Herrero, C. P.

    2012-10-01

    The phase diagram of ice Ih, II, and III is studied by a quasi-harmonic approximation. The results of this approach are compared to phase diagrams previously derived by thermodynamic integration using path integral and classical simulations, as well as to experimental data. The studied models are based on both flexible (q-TIP4P/F) and rigid (TIP4P/2005, TIP4PQ/2005) descriptions of the water molecule. Many aspects of the simulated phase diagrams are reasonably reproduced by the quasi-harmonic approximation. Advantages of this simple approach are that it is free from the statistical errors inherent to computer simulations, both classical and quantum limits are easily accessible, and the error of the approximation is expected to decrease in the zero temperature limit. We find that the calculated phase diagram of ice Ih, II, and III depends strongly on the hydrogen disorder of ice III, at least for cell sizes typically used in phase coexistence simulations. Either ice II (in the classical limit) or ice III (in the quantum one) may become unstable depending upon the proton disorder in ice III. The comparison of quantum and classical limits shows that the stabilization of ice II is the most important quantum effect in the phase diagram. The lower vibrational zero-point energy of ice II, compared to either ice Ih or III, is the microscopic origin of this stabilization. The necessity of performing an average of the lattice energy over the proton disorder of ice III is discussed.

  4. Development of active vibration isolation system for precision machines

    NASA Astrophysics Data System (ADS)

    Li, H. Z.; Lin, W. J.; Yang, G. L.

    2010-03-01

    It is a common understanding by manufacturers of precision machines that vibrations are a potentially disastrous threat to precision and throughput. To satisfy the quest for more stable processes and tighter critical dimension control in the microelectronics manufacturing industry, active vibration control becomes increasingly important for high-precision equipment developers. This paper introduced the development of an active vibration isolation system for precision machines. Innovative mechatronic approaches are investigated that can effectively suppress both environmental and payload-generated vibration. In this system, accelerometers are used as the feedback sensor, voice coil motors are used to generate the counter force, and a TI DSP controller is used to couple sensor measurements to actuator forces via specially designed control algorithms in real-time to counteract the vibration disturbances. Experimental results by using the developed AVI prototype showed promising performance on vibration attenuation. It demonstrated a reduction of the settling time from 2s to 0.1s under impulsive disturbances; and a vibration attenuation level of more than 20dB for harmonic disturbances. The technology can be used to suppress vibration for a wide range of precision machines to achieve fast settling time and higher accuracy.

  5. Development of active vibration isolation system for precision machines

    NASA Astrophysics Data System (ADS)

    Li, H. Z.; Lin, W. J.; Yang, G. L.

    2009-12-01

    It is a common understanding by manufacturers of precision machines that vibrations are a potentially disastrous threat to precision and throughput. To satisfy the quest for more stable processes and tighter critical dimension control in the microelectronics manufacturing industry, active vibration control becomes increasingly important for high-precision equipment developers. This paper introduced the development of an active vibration isolation system for precision machines. Innovative mechatronic approaches are investigated that can effectively suppress both environmental and payload-generated vibration. In this system, accelerometers are used as the feedback sensor, voice coil motors are used to generate the counter force, and a TI DSP controller is used to couple sensor measurements to actuator forces via specially designed control algorithms in real-time to counteract the vibration disturbances. Experimental results by using the developed AVI prototype showed promising performance on vibration attenuation. It demonstrated a reduction of the settling time from 2s to 0.1s under impulsive disturbances; and a vibration attenuation level of more than 20dB for harmonic disturbances. The technology can be used to suppress vibration for a wide range of precision machines to achieve fast settling time and higher accuracy.

  6. ROTATION-VIBRATION TETRAHEDRAL

    E-print Network

    Sadovskií, Dmitrií

    ANALYSIS OF ROTATION-VIBRATION RELATIVE EQUILIBRIA ON THE EXAMPLE OF A TETRAHEDRAL FOUR ATOM (RE) of a nonrigid molecule which vibrates about a well de#12;ned equilibrium con#12;guration and rotates as a whole. Our analysis uni#12;es the theory of rotational and vibrational RE. We rely

  7. calculators hp calculators

    E-print Network

    Vetter, Frederick J.

    calculators hp calculators HP 50g Working with Parametric Plots Plotting on the HP 50g Parametric calculators HP 50g Working with Parametric Plots hp calculators - 2 - HP 50g Working with Parametric Plots Plotting on the HP 50g The HP 50g calculator provides a host of plots to allow the user to visualize data

  8. Molecular structure, vibrational spectroscopic, hyperpolarizability, natural bond orbital analysis, frontier molecular orbital analysis and thermodynamic properties of 2,3,4,5,6-pentafluorophenylacetic acid.

    PubMed

    Balachandran, V; Karunakaran, V

    2014-06-01

    The FT-IR (4000-400cm(-)(1)) and FT-Raman spectra (3500-100cm(-)(1)) of 2,3,4,5,6-pentafluorophenylacetic acid (PAA) have been recorded. Density functional theory calculation with LSDA/6-31+G(d,p) and B3LYP/6-31+G(d,p) basis sets have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman intensities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of PAA are calculated using B3LYP/6-31+G(d,p) method on the finite-field approach. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within this molecule. Mulliken population analysis on atomic charges is also calculated. Thermodynamic properties (heat capacity, enthalpy, Gibb's free energy and entropy) of the title compound at different temperatures were calculated. PMID:24662720

  9. Molecular structure, vibrational spectroscopic, hyperpolarizability, natural bond orbital analysis, frontier molecular orbital analysis and thermodynamic properties of 2,3,4,5,6-pentafluorophenylacetic acid

    NASA Astrophysics Data System (ADS)

    Balachandran, V.; Karunakaran, V.

    2014-06-01

    The FT-IR (4000-400 cm-1) and FT-Raman spectra (3500-100 cm-1) of 2,3,4,5,6-pentafluorophenylacetic acid (PAA) have been recorded. Density functional theory calculation with LSDA/6-31+G(d,p) and B3LYP/6-31+G(d,p) basis sets have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman intensities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of PAA are calculated using B3LYP/6-31+G(d,p) method on the finite-field approach. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within this molecule. Mulliken population analysis on atomic charges is also calculated. Thermodynamic properties (heat capacity, enthalpy, Gibb's free energy and entropy) of the title compound at different temperatures were calculated.

  10. Ioffe-Regel criterion and diffusion of vibrations in random lattices

    NASA Astrophysics Data System (ADS)

    Beltukov, Y. M.; Kozub, V. I.; Parshin, D. A.

    2013-04-01

    Using a stable random matrix approach, we consider the diffusion of vibrations in 3d harmonic lattices with strong force-constant disorder. Above some frequency ?IR, corresponding to the Ioffe-Regel crossover, the notion of phonons becomes ill defined. They cannot propagate through the system and transfer energy. Nevertheless, most of the vibrations in this range are not localized. We show that they are similar to diffusons introduced by Allen [P. B. Allen, J. L. Feldman, J. Fabian, and F. Wooten, Phil. Mag. B1364-281210.1080/13642819908223054 79, 1715 (1999)] to describe heat transport in glasses. The crossover frequency ?IR is close to the position of the boson peak. By changing the strength of disorder we can vary ?IR from zero value (when the rigidity is zero and there are no phonons in the lattice) up to a typical frequency in the system. Above ?IR, the energy in the lattice is transferred by means of diffusion of vibrational excitations. We calculated the diffusivity of the modes D(?) using both the direct numerical solution of the Newton equations and the formula of Edwards and Thouless. It is nearly a constant above ?IR and goes to zero at the localization threshold. We show that apart from the diffusion of energy, a diffusion of particle displacements in the lattice takes place as well. Above ?IR, a displacement structure factor S(q,?) coincides well with a structure factor of random walk on the lattice. As a result, the vibrational line width is ?(q)=Duq2, where Du is a diffusion coefficient of particle displacements. These findings may be important for the interpretation of experimental data on inelastic x-ray scattering and mechanisms of heat transfer in glasses. We also show that the scaling with model parameters in our model maps directly onto the scaling observed in the jamming transition model.

  11. Pure-tone birdsong by resonance filtering of harmonic overtones

    PubMed Central

    Beckers, Gabriël J. L.; Suthers, Roderick A.; Cate, Carel ten

    2003-01-01

    Pure-tone song is a common and widespread phenomenon in birds. The mechanistic origin of this type of phonation has been the subject of long-standing discussion. Currently, there are three hypotheses. (i) A vibrating valve in the avian vocal organ, the syrinx, generates a multifrequency harmonic source sound, which is filtered to a pure tone by a vocal tract filter (“source-filter” model, analogous to human speech production). (ii) Vocal tract resonances couple with a vibrating valve source, suppressing the normal production of harmonic overtones at this source (“soprano” model, analogous to human soprano singing). (iii) Pure-tone sound is produced as such by a sound-generating mechanism that is fundamentally different from a vibrating valve. Here we present direct evidence of a source-filter mechanism in the production of pure-tone birdsong. Using tracheal thermistors and air sac pressure cannulae, we recorded sound signals close to the syringeal sound source during spontaneous, pure-tone vocalizations of two species of turtledove. The results show that pure-tone dove vocalizations originate through filtering of a multifrequency harmonic sound source. PMID:12764226

  12. Pure-tone birdsong by resonance filtering of harmonic overtones.

    PubMed

    Beckers, Gabriël J L; Suthers, Roderick A; ten Cate, Carel

    2003-06-10

    Pure-tone song is a common and widespread phenomenon in birds. The mechanistic origin of this type of phonation has been the subject of long-standing discussion. Currently, there are three hypotheses. (i) A vibrating valve in the avian vocal organ, the syrinx, generates a multifrequency harmonic source sound, which is filtered to a pure tone by a vocal tract filter ("source-filter" model, analogous to human speech production). (ii) Vocal tract resonances couple with a vibrating valve source, suppressing the normal production of harmonic overtones at this source ("soprano" model, analogous to human soprano singing). (iii) Pure-tone sound is produced as such by a sound-generating mechanism that is fundamentally different from a vibrating valve. Here we present direct evidence of a source-filter mechanism in the production of pure-tone birdsong. Using tracheal thermistors and air sac pressure cannulae, we recorded sound signals close to the syringeal sound source during spontaneous, pure-tone vocalizations of two species of turtledove. The results show that pure-tone dove vocalizations originate through filtering of a multifrequency harmonic sound source. PMID:12764226

  13. Selection rules for harmonic generation in solids

    NASA Astrophysics Data System (ADS)

    Moiseyev, Nimrod

    2015-05-01

    High-order harmonic generation (HHG) in a bulk crystal was first observed in 2011 [S. Ghimire, A. D. DiChiara, E. Sistrunk, P. Agostini, L. F. DiMauro, and D. A. Reis, Nat. Phys. 7, 138 (2011), 10.1038/nphys1847]. Only odd-order harmonics were observed as expected on the basis of the selection rules in solids, which were derived when only the interband currents were taken into consideration. Here we study HHG in solids when the intraband currents are taken into consideration as well. We show that the dynamical selection rules are broken in solids and the possibility of generation of even-order harmonics cannot be excluded on the basis of the dynamical symmetry analysis. However, a simple analysis of the expression we obtained for the amplitude of the emitted high-order harmonics shows, without the need to carry out numerical calculations, that the even-order harmonics are suppressed due to the localization of the field-free one-electron density probability on the atoms in the solids.

  14. Vibrational Spectra of Xanthione and Xanthone

    NASA Astrophysics Data System (ADS)

    Sinha, H. K.; Chantranupong, L.; Steer, R. P.

    1995-02-01

    The fundamental vibrational frequencies of xanthione (XT) and xanthone (XN), two structurally similar heteroaromatic molecules, have been obtained experimentally using FTIR and Raman spectroscopy. Ab initio RHF/STO-3G?? and RHF/CEP-31G and semiempirical RHF/AM1 and RHF/PM3 molecular orbital calculations have been performed to obtain the vibrational frequencies of these molecules from their force fields. A comparison of the experimental and calculated frequencies reveals that all four theoretical methods overestimate the vibrational frequencies and that the rms deviations increase in the order CEP-31G < STO-3G?? < PM3 < AM1. The frequencies obtained by the effective core potential, CEP-31G, method are in excellent agreement with experiment when the calculated frequencies are scaled uniformly by a factor of 0.8953.

  15. Direct quantum mechanical/molecular mechanical simulations of two-dimensional vibrational responses: N-methylacetamide in water

    NASA Astrophysics Data System (ADS)

    Jeon, Jonggu; Cho, Minhaeng

    2010-06-01

    Multidimensional infrared (IR) spectroscopy has emerged as a viable tool to study molecular structure and dynamics in condensed phases, and the third-order vibrational response function is the central quantity underlying various nonlinear IR spectroscopic techniques, such as pump-probe, photon echo and two-dimensional (2D) IR spectroscopy. In this paper, a new computational method is presented that calculates this nonlinear response function in the classical limit from a series of classical molecular dynamics (MD) simulations, employing a quantum mechanical/molecular mechanical (QM/MM) force field. The method relies on the stability matrix formalism where the dipole-dipole quantum mechanical commutators appearing in the exact quantum response function are replaced by the corresponding Poisson brackets. We present the formulation and computational algorithm of the method for both the classical and the QM/MM force fields and apply it to the 2D IR spectroscopy of carbon monoxide (CO) and N-methylacetamide (NMA), each solvated in a water cluster. The conventional classical force field with harmonic bond potentials is shown to be incapable of producing a reliable 2D IR signal because intramolecular vibrational anharmonicity, essential to the production of the nonlinear signal, is absent in such a model. The QM/MM force field, on the other hand, produces distinct 2D spectra for the NMA and CO systems with clear vertical splitting and cross peaks, reflecting the vibrational anharmonicities and the vibrational couplings between the underlying vibrational modes, respectively. In the NMA spectrum, the coupling between the amide I and II modes is also well reproduced. While attaining the converged spectrum is found to be challenging with this method, with an adequate amount of computing it can be straightforwardly applied to new systems containing multiple chromophores with little modeling effort, and therefore it would be useful in understanding the multimode 2D IR spectrum of complex molecular systems.

  16. Molecular structure, vibrational spectra, NLO and NBO analysis of bis(8-oxy-1-methylquinolinium) hydroiodide.

    PubMed

    Pir, H; Günay, N; Avc?, D; Atalay, Y

    2012-10-01

    In this paper, quantum chemistry calculations of geometric parameters, harmonic vibrational wavenumbers, molecular frontier orbital energies (HOMO and LUMO) and the electronic properties of bis(8-oxy-1-methylquinolinium) hydroiodide ([(C(10)H(9)NO)(2)H(+)]·I(-)) have been performed by using Gaussian 09 program. The structural and spectroscopic data of the molecule in the ground state have been calculated by using Hartree-Fock (HF) and density functional method (DFT/B3LYP) with the LanL2DZ basis set. For the spectra predicted, a potential energy distribution (PED) is calculated. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts values of bis(8-oxy-1-methylquinolinium) hydroiodide molecule have been calculated by the gage including atomic orbital (GIAO) method. Furthermore, molecular electrostatic potential maps (MEP), Mulliken charges and the natural bonding orbital (NBO) analysis of the compound have been calculated by the HF and B3LYP/Lanl2DZ methods. PMID:22954808

  17. A strong Nsbnd H…Br vibrational behaviour studied through X-ray, vibrational spectra and quantum chemical studies in an isomorphous crystal: 2-Nitroanilinium bromide

    NASA Astrophysics Data System (ADS)

    Anitha, R.; Athimoolam, S.; Gunasekaran, M.

    2015-03-01

    A needle shaped transparent light brown crystals of 2-nitroanilinium bromide were successfully synthesized and crystallized from an aqueous mixture by slow evaporation technique. Single crystal XRD studies confirm the crystalline phase of this isomorphous compound which contains a positively charge 2-nitroanilinium cation and a negatively charged bromide anion. The solid phase FT-IR and FT-Raman spectra of the compound have been recorded in the range of 4000-400 cm-1. The observed modes are correlated by the factor group theory analysis and different IR and Raman active species were identified. Geometrical optimisations were carried out and harmonic vibrational wave numbers were computed for the minimum energy molecular structure at RHF level invoking 6-311++G(d,p) and SDD basis sets. Optimised molecular geometry was compared with the crystallographic data. The calculated wavenumbers were compared with the experimental values. The Nsbnd H vibrational bands are shifted from its normal range and the shifting is associated with the influence of the intermolecular hydrogen bonds in the crystal. A strong intensity peak in theoretical and corresponding band in experimental confirms the presence of Nsbnd H…Br interaction as predicted in crystalline state.

  18. A strong NH…Br vibrational behaviour studied through X-ray, vibrational spectra and quantum chemical studies in an isomorphous crystal: 2-Nitroanilinium bromide.

    PubMed

    Anitha, R; Athimoolam, S; Gunasekaran, M

    2015-03-01

    A needle shaped transparent light brown crystals of 2-nitroanilinium bromide were successfully synthesized and crystallized from an aqueous mixture by slow evaporation technique. Single crystal XRD studies confirm the crystalline phase of this isomorphous compound which contains a positively charge 2-nitroanilinium cation and a negatively charged bromide anion. The solid phase FT-IR and FT-Raman spectra of the compound have been recorded in the range of 4000-400cm(-1). The observed modes are correlated by the factor group theory analysis and different IR and Raman active species were identified. Geometrical optimisations were carried out and harmonic vibrational wave numbers were computed for the minimum energy molecular structure at RHF level invoking 6-311++G(d,p) and SDD basis sets. Optimised molecular geometry was compared with the crystallographic data. The calculated wavenumbers were compared with the experimental values. The NH vibrational bands are shifted from its normal range and the shifting is associated with the influence of the intermolecular hydrogen bonds in the crystal. A strong intensity peak in theoretical and corresponding band in experimental confirms the presence of NH…Br interaction as predicted in crystalline state. PMID:25544191

  19. A direct evidence of vibrationally delocalized response at ice surface

    SciTech Connect

    Ishiyama, Tatsuya; Morita, Akihiro, E-mail: morita@m.tohoku.ac.jp [Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan)

    2014-11-14

    Surface-specific vibrational spectroscopic responses at isotope diluted ice and amorphous ice are investigated by molecular dynamics (MD) simulations combined with quantum mechanics/molecular mechanics calculations. The intense response specific to the ordinary crystal ice surface is predicted to be significantly suppressed in the isotopically diluted and amorphous ices, demonstrating the vibrational delocalization at the ordinary ice surface. The collective vibration at the ice surface is also analyzed with varying temperature by the MD simulation.

  20. A direct evidence of vibrationally delocalized response at ice surface

    NASA Astrophysics Data System (ADS)

    Ishiyama, Tatsuya; Morita, Akihiro

    2014-11-01

    Surface-specific vibrational spectroscopic responses at isotope diluted ice and amorphous ice are investigated by molecular dynamics (MD) simulations combined with quantum mechanics/molecular mechanics calculations. The intense response specific to the ordinary crystal ice surface is predicted to be significantly suppressed in the isotopically diluted and amorphous ices, demonstrating the vibrational delocalization at the ordinary ice surface. The collective vibration at the ice surface is also analyzed with varying temperature by the MD simulation.