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1

A harmonic adiabatic approximation to calculate highly excited vibrational levels of ``floppy molecules''  

NASA Astrophysics Data System (ADS)

The harmonic adiabatic approximation (HADA), an efficient and accurate quantum method to calculate highly excited vibrational levels of molecular systems, is presented. It is well-suited to applications to ``floppy molecules'' with a rather large number of atoms (N>3). A clever choice of internal coordinates naturally suggests their separation into active, slow, or large amplitude coordinates q', and inactive, fast, or small amplitude coordinates q'', which leads to an adiabatic (or Born-Oppenheimer-type) approximation (ADA), i.e., the total wave function is expressed as a product of active and inactive total wave functions. However, within the framework of the ADA, potential energy data concerning the inactive coordinates q'' are required. To reduce this need, a minimum energy domain (MED) is defined by minimizing the potential energy surface (PES) for each value of the active variables q', and a quadratic or harmonic expansion of the PES, based on the MED, is used (MED harmonic potential). In other words, the overall picture is that of a harmonic valley about the MED. In the case of only one active variable, we have a minimum energy path (MEP) and a MEP harmonic potential. The combination of the MED harmonic potential and the adiabatic approximation (harmonic adiabatic approximation: HADA) greatly reduces the size of the numerical computations, so that rather large molecules can be studied. In the present article however, the HADA is applied to our benchmark molecule HCN/CNH, to test the validity of the method. Thus, the HADA vibrational energy levels are compared and are in excellent agreement with the ADA calculations (adiabatic approximation with the full PES) of Light and Ba?i? [J. Chem. Phys. 87, 4008 (1987)]. Furthermore, the exact harmonic results (exact calculations without the adiabatic approximation but with the MEP harmonic potential) are compared to the exact calculations (without any sort of approximation). In addition, we compare the densities of the bending motion during the HCN/CNH isomerization, computed with the HADA and the exact wave function.

Lauvergnat, David; Nauts, André; Justum, Yves; Chapuisat, Xavier

2001-04-01

2

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

PubMed

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 using 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 in the energy calculations amount to 36N - 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 (water dimer and trimer) are presented. In all cases the frequencies based on internal coordinates differ on average by <1 cm(-1) from those obtained from Cartesian coordinates. PMID:23406376

Miliordos, Evangelos; Xantheas, Sotiris S

2013-03-05

3

Harmonic calculations and measurements of the irreversibility field using a vibrating sample magnetometer  

NASA Astrophysics Data System (ADS)

The effect of the field inhomogeneity of the magnet on a vibrating sample magnetometer (VSM) measurement of a superconductor is calculated using Bean's model and Mallinson's principle of reciprocity. When the sample is centered in both the magnetic field and the VSM pick-up coils, the hysteretic signal obtained in a VSM measurement, associated with the critical current density (JC), is reduced to zero when the effective ac field caused by the sample movement penetrates the entire sample and not, as is commonly assumed, when the critical current density becomes zero. Under these conditions, an apparent phase transition is observed where the magnitude of the hysteresis drops to zero over a small field range. This apparent transition is solely an artifact of the measurement and cannot correctly be compared to theoretical calculations of the irreversibility field (BIRR), which is the phase boundary at which JC is zero. Furthermore, the apparent reversible magnetization signal in high fields includes two contributions. In addition to the usual diamagnetic contribution from the thermodynamic reversible magnetization of the superconductor, there is a reversible paramagnetic contribution from the nonzero JC. Hence values of the Ginzburg-Landau parameter (?) cannot be reliably obtained from standard reversible magnetization measurements using a VSM unless it is confirmed that JC is zero. Harmonic measurements using a VSM are reported. They confirm the results of the calculations. By applying a large field gradient, the hysteresis in the magnetization signal at the drive frequency of the VSM is found to drop to zero more than 3 T below BIRR. We propose methods to improve measurements of BIRR and ?. The implications of results presented for superconducting quantum interference device measurements are also briefly discussed.

Daniel, Ian J.; Hampshire, Damian P.

2000-03-01

4

Vibrational and thermal properties of ScN and YN: quasi-harmonic approximation calculations and anharmonic effects  

NASA Astrophysics Data System (ADS)

The structural, vibrational and thermal properties of rocksalt ScN and YN are investigated by using a first-principles plane-wave approach. The results are discussed in comparison with the similarly calculated results for rocksalt MgO and zincblende AlN. The thermal expansivity (?V) computed within the quasi-harmonic approximation shows that there are significant anharmonic effects in ScN and YN, which are comparable to those in MgO. Since no experimental results are available for ?V of either ScN or YN, the anharmonic effects are accounted for by a variant of the very recently introduced effective semiempirical ansatz (Phys. Rev. B 2009 79 104304) for calculating anharmonic free energy, which does not require any input from experiment. The validity of this very simple approach is demonstrated first by applying it to MgO. For the considered phase of AlN, the quasi-harmonic approximation is valid up to very high temperatures, and the thus obtained ?V is in good agreement with experiment. The values of ?V for semiconductor transition metal nitrides that crystallize in the rocksalt phase are higher than those for the zincblende phase of group-IIIB nitrides, and a major part of these differences is due to the crystal structure.

Tahri, Salma; Qteish, Abdallah; Al-Qasir, Iyad I.; Meskini, Noureddine

2012-01-01

5

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)

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.

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

2013-01-01

6

Vibrational spectroscopy of (SO4(2-)).(H2O)n clusters, n=1-5: harmonic and anharmonic calculations and experiment.  

PubMed

The vibrational spectroscopy of (SO4(2-)).(H2O)n is studied by theoretical calculations for n=1-5, and the results are compared with experiments for n=3-5. The calculations use both ab initio MP2 and DFT/B3LYP potential energy surfaces. Both harmonic and anharmonic calculations are reported, the latter with the CC-VSCF method. The main findings are the following: (1) With one exception (H2O bending mode), the anharmonicity of the observed transitions, all in the experimental window of 540-1850 cm(-1), is negligible. The computed anharmonic coupling suggests that intramolecular vibrational redistribution does not play any role for the observed linewidths. (2) Comparison with experiment at the harmonic level of computed fundamental frequencies indicates that MP2 is significantly more accurate than DFT/B3LYP for these systems. (3) Strong anharmonic effects are, however, calculated for numerous transitions of these systems, which are outside the present observation window. These include fundamentals as well as combination modes. (4) Combination modes for the n=1 and n=2 clusters are computed. Several relatively strong combination transitions are predicted. These show strong anharmonic effects. (5) An interesting effect of the zero point energy (ZPE) on structure is found for (SO4(2-)).(H2O)(5): The global minimum of the potential energy corresponds to a C(s) structure, but with incorporation of ZPE the lowest energy structure is C2v, in accordance with experiment. (6) No stable structures were found for (OH-).(HSO4-).(H2O)n, for n

Miller, Yifat; Chaban, Galina M; Zhou, Jia; Asmis, Knut R; Neumark, Daniel M; Gerber, R Benny

2007-09-01

7

An investigation into the vibration of harmonic drive systems  

NASA Astrophysics Data System (ADS)

Harmonic drive systems are precise and specific transmission gear systems which are beneficial in terms of the high transmission ratio and almost zero backlash. These inherent and spectacular properties result in using this mechanism in robotic and space sciences where the precision and lightwieght play an important role. This paper presents a vibration analysis of harmonic drive systems using the shell theory. Equations of vibration for the flexspline and the circular spline of the system are derived and used to find the natural frequencies for both parts and, moreover, vibration response of the system under the operating condition is calculated. Also, obtained vibration equations are utilized to study the effects of different involved parameters such as the geometry of the flexspline and its gear tooth, eccentricity, and unbalancing on the vibrational behavior of the system.

Masoumi, M.; Alimohammadi, H.

2013-09-01

8

Harmonic Vibrations of Elastic Plates with Separate Ribs.  

National Technical Information Service (NTIS)

Reported is a description of a method of calculating the harmonic vibrations of elastic rectangular plates which are freely supported at two edges and are reinforced vertically with eccentric ribs. First the plate edge shear forces for the bending and she...

D. Werner

1972-01-01

9

Lattice Vibrations and Harmonic Forces in Solids  

Microsoft Academic Search

A discussion is given of the interpretation in terms of harmonic forces between atoms of the phonon frequency against wave vector data which is provided by the results of both X-ray and neutron scattering experiments. A knowledge of the phonon polarization vectors is required before a calculation of the components of the interatomic harmonic force tensors between all neighbour atom

A J E Foreman; W M Lomer

1957-01-01

10

Probing nuclear vibration using high-order harmonic generation  

NASA Astrophysics Data System (ADS)

We point out the possibility of probing the nuclear vibration by using the high-order harmonic generation (HHG) with ultrashort laser pulses. By analyzing the HHG spectra obtained from the numerical solution of the time-dependent Schrödinger equation, we find that the intensity of the emitted harmonics is strongly determined not only by the molecular configuration but also by the initial velocity of nuclei. The calculations show that the intensity of HHG is enhanced nearly the time when the internuclear separation takes the equilibrium value and the nuclei are moving closer together. In contrast, with the same initial internuclear separation but with the opposite direction of nuclear velocity, the intensity of emitted light is reduced noticeably. We use that evidence as a tool to probe the nuclear vibration.

Nguyen, Ngoc-Ty; Hoang, Van-Hung; Le, Van-Hoang

2013-08-01

11

Harmonic Vibrations of Elastic Plates in a Subsonic Stream.  

National Technical Information Service (NTIS)

The article contains a purely theoretical study on harmonic vibrations of elastic airfoils in a subsonic stream of different properties. The study considers an infinite wing and, assuming it an elastic flat plate, investigates its own vibrations, taking i...

G. I. Kopzon

1967-01-01

12

Adaptive control system for vibration harmonics of cryocooler  

NASA Astrophysics Data System (ADS)

Vibration disturbances generated by cryocooler, representing in a series of harmonics, are critical issue in practical application. A control system including electronic circuit and mechanical actuator has been developed to attenuate the vibration. The control algorithm executes as a series of adaptive narrowband notch filters to reduce corresponding harmonics. The algorithm does not require actuator transfer function, thus ensure its adaptiveness. Using this algorithm, all the vibration harmonics of cryocooler were attenuated by a factor of more than 45.9 dB, i.e., the residual vibration force was reduced from 20.1Nrms to 0.102Nrms over the 300 Hz control bandwidth, the converging time is only less than 20 seconds, and the power consumption of mechanical actuator is less than half a watt. The vibration control system has achieved the general requirement of Infrared application.

Yang, Baoyu; Wu, Yinong

2013-06-01

13

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

SciTech Connect

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.

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

14

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

ERIC Educational Resources Information Center

|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.|

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

2004-01-01

15

Higher Harmonic Blade Pitch Control for Helicopter Vibration Reduction: A Feasibility Study.  

National Technical Information Service (NTIS)

The concept of eliminating most helicopter vibration by changing certain rotor harmonic airloads and blade motions with harmonic pitch control is discussed in detail. A simple method of obtaining the required pitch harmonics by periodic tilting of the swa...

J. Shaw

1968-01-01

16

Vibration response and harmonic wave propagation of ultrasonic arc drivers  

NASA Astrophysics Data System (ADS)

A piezoelectric curvilinear arc driver designed for an ultrasonic curvilinear motor is evaluated in this study. A design of piezoelectric curvilinear arc driver is proposed and its governing equations, vibration behaviour and wave propagation are investigated. Then, analysis of forced vibration response or driving characteristics to harmonic excitations in the modal domain is conducted. Finite element modelling and analysis of the arc driver are also discussed. Analytical results of free vibration characteristics are compared favourably with the finite element results. Harmonic analyses of the three finite element models reveal changes of dynamic behaviours of three models and also imply operating frequencies with a significant travelling wave component. Parametric study of mathematical and finite element simulation results suggests that stable travelling waves can be generated to drive a rotor on the proposed curvilinear arc motor system.

Smithmaitrie, Pruittikorn; Dehaven, J. G.; Higuchi, K.; Tzou, H. S.

2007-02-01

17

Calculation of vibrational transition frequencies and intensities in water dimer: comparison of different vibrational approaches.  

PubMed

We have calculated frequencies and intensities of fundamental and overtone vibrational transitions in water and water dimer with use of different vibrational methods. We have compared results obtained with correlation-corrected vibrational self-consistent-field theory and vibrational second-order perturbation theory both using normal modes and finally with a harmonically coupled anharmonic oscillator local mode model including OH-stretching and HOH-bending local modes. The coupled cluster with singles, doubles, and perturbative triples ab initio method with augmented correlation-consistent triple-zeta Dunning and atomic natural orbital basis sets has been used to obtain the necessary potential energy and dipole moment surfaces. We identify the strengths and weaknesses of these different vibrational approaches and compare our results to the available experimental results. PMID:18407701

Kjaergaard, Henrik G; Garden, Anna L; Chaban, Galina M; Gerber, R Benny; Matthews, Devin A; Stanton, John F

2008-04-12

18

Variational calculations of vibrational properties of ozone  

Microsoft Academic Search

A variational method is used to obtain vibrational-rotational properties for ozone from an experimental quartic force field. Band positions, average structures, matrix elements for calculating infrared intensities, and effective rotational constants are reported for (O-16)3 and its O-18 isotopic species. Also, the degree to which the vibrational energies and properties are converged is investigated as a function of the basis

G. D. Carney; L. A. Curtiss; S. R. Langhoff

1977-01-01

19

Variational calculations of vibrational properties of ozone  

Microsoft Academic Search

A variational method is used to obtain vibrational–rotational properties for ozone from an experimental quartic force field. Band positions, average structures, matrix elements for calculating infrared intensities, and effective rotational constants are reported for 16O3 and its 18O isotopic species. Also, the degree to which the vibrational energies and properties are converged is investigated as a function of the basis

G. D. Carney; S. R. Langhoff; L. A. Curtisst

1977-01-01

20

Piezoelectric MEMS energy harvesting systems driven by harmonic and random vibrations  

Microsoft Academic Search

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

Lars-Cyril Blystad; Einar Halvorsen; Svein Husa

2010-01-01

21

Vibrational spectroscopic studies and DFT calculations of 4-aminoantipyrine  

NASA Astrophysics Data System (ADS)

The pyrazole derivative, 4-aminoantipyrine (4AAP), used as an intermediate for the synthesis of pharmaceuticals especially antipyretic and analgesic drugs has been analyzed experimentally and theoretically for its vibrational frequencies. The FTIR and FT Raman spectra of the title compound have been compared with the theoretically computed frequencies invoking the standard 6-311g(d,p) and cc-pVDZ basis sets at DFT level of theory (B3LYP). The harmonic vibrational frequencies at B3LYP/cc-pVDZ after appropriate scaling method seem to coincide satisfactorily with the experimental observations rather than B3LYP/6-311g(d,p) results. The theoretical spectrograms for FT-IR and FT-Raman spectra of 4AAP have been also constructed and compared with the experimental spectra. Additionally, thermodynamic data have also been calculated and discussed.

Swaminathan, J.; Ramalingam, M.; Sethuraman, V.; Sundaraganesan, N.; Sebastian, S.

2009-08-01

22

Vibrational spectroscopy and relaxation of an anharmonic oscillator coupled to harmonic bath.  

PubMed

The vibrational spectroscopy and relaxation of an anharmonic oscillator coupled to a harmonic bath are examined to assess the applicability of the time correlation function (TCF), the response function, and the semiclassical frequency modulation (SFM) model to the calculation of infrared (IR) spectra. These three approaches are often used in connection with the molecular dynamics simulations but have not been compared in detail. We also analyze the vibrational energy relaxation (VER), which determines the line shape and is itself a pivotal process in energy transport. The IR spectra and VER are calculated using the generalized Langevin equation (GLE), the Gaussian wavepacket (GWP) method, and the quantum master equation (QME). By calculating the vibrational frequency TCF, a detailed analysis of the frequency fluctuation and correlation time of the model is provided. The peak amplitude and width in the IR spectra calculated by the GLE with the harmonic quantum correction are shown to agree well with those by the QME though the vibrational frequency is generally overestimated. The GWP method improves the peak position by considering the zero-point energy and the anharmonicity although the red-shift slightly overshoots the QME reference. The GWP also yields an extra peak in the higher-frequency region than the fundamental transition arising from the difference frequency of the center and width oscillations of a wavepacket. The SFM approach underestimates the peak amplitude of the IR spectra but well reproduces the peak width. Further, the dependence of the VER rate on the strength of an excitation pulse is discussed. PMID:21639460

Joutsuka, Tatsuya; Ando, Koji

2011-05-28

23

Vibrational structure theory: new vibrational wave function methods for calculation of anharmonic vibrational energies and vibrational contributions to molecular properties.  

PubMed

A number of recently developed theoretical methods for the calculation of vibrational energies and wave functions are reviewed. Methods for constructing the appropriate quantum mechanical Hamilton operator are briefly described before reviewing a particular branch of theoretical methods for solving the nuclear Schrödinger equation. The main focus is on wave function methods using the vibrational self-consistent field (VSCF) as starting point, and includes vibrational configuration interaction (VCI), vibrational Mřller-Plesset (VMP) theory, and vibrational coupled cluster (VCC) theory. The convergence of the different methods towards the full vibrational configuration interaction (FVCI) result is discussed. Finally, newly developed vibrational response methods for calculation of vibrational contributions to properties, energies, and transition probabilities are discussed. PMID:17551617

Christiansen, Ove

2007-03-23

24

Vibrational spectra and DFT calculations of squalene  

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

25

Modeling, calculating, and analyzing multidimensional vibrational spectroscopies.  

PubMed

Spectral line shapes in a condensed phase contain information from various dynamic processes that modulate the transition energy, such as microscopic dynamics, inter- and intramolecular couplings, and solvent dynamics. Because nonlinear response functions are sensitive to the complex dynamics of chemical processes, multidimensional vibrational spectroscopies can separate these processes. In multidimensional vibrational spectroscopy, the nonlinear response functions of a molecular dipole or polarizability are measured using ultrashort pulses to monitor inter- and intramolecular vibrational motions. Because a complex profile of such signals depends on the many dynamic and structural aspects of a molecular system, researchers would like to have a theoretical understanding of these phenomena. In this Account, we explore and describe the roles of different physical phenomena that arise from the peculiarities of the system-bath coupling in multidimensional spectra. We also present simple analytical expressions for a weakly coupled multimode Brownian system, which we use to analyze the results obtained by the experiments and simulations. To calculate the nonlinear optical response, researchers commonly use a particular form of a system Hamiltonian fit to the experimental results. The optical responses of molecular vibrational motions have been studied in either an oscillator model or a vibration energy state model. In principle, both models should give the same results as long as the energy states are chosen to be the eigenstates of the oscillator model. The energy state model can provide a simple description of nonlinear optical processes because the diagrammatic Liouville space theory that developed in the electronically resonant spectroscopies can easily handle three or four energy states involved in high-frequency vibrations. However, the energy state model breaks down if we include the thermal excitation and relaxation processes in the dynamics to put the system in a thermal equilibrium state. The roles of these excitation and relaxation processes are different and complicated compared with those in the resonant spectroscopy. Observing the effects of such thermal processes is more intuitive with the oscillator model because the bath modes, which cause the fluctuation and dissipation processes, are also described in the coordinate space. This coordinate space system-bath approach complements a realistic full molecular dynamics simulation approach. By comparing the calculated 2D spectra from the coordinate space model and the energy state model, we can examine the role of thermal processes and anharmonic mode-mode couplings in the energy state model. For this purpose, we employed the Brownian oscillator model with the nonlinear system-bath interaction. Using the hierarchy formalism, we could precisely calculate multidimensional spectra for a single and multimode anharmonic system for inter- and intramolecular vibrational modes. PMID:19441802

Tanimura, Yoshitaka; Ishizaki, Akihito

2009-09-15

26

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

PubMed Central

A previous report [Margolis and Stiepan (2012). “Acoustic method for calibration of audiometric bone vibrators,” J. Acoust. Soc. Am. 131, 1221–1225] described a reliable, inexpensive, acoustic method for calibration of audiometric bone vibrators. As a follow up to that report harmonic distortion measurements were made with the standard electromechanical method and the acoustic method using five Radioear B71 vibrators and one Radioear B81 prototype vibrator. Lower distortion was seen for measurements made with the acoustic method compared to the electromechanical method and for the Radioear B81 vibrator compared to the Radioear B71 vibrator.

Ginter, Samantha M.; Margolis, Robert H.

2013-01-01

27

Nonlinear response of a harmonic diatomic molecule: Algebraic nonperturbative calculation  

SciTech Connect

Even harmonic molecules display a nonlinear behavior when driven by an inhomogeneous field. We calculate the response of single harmonic molecules to a monochromatic time and space dependent electric field E(r,t) of frequency {omega} employing exact algebraic methods. We evaluate the responses at the fundamental frequency {omega} and at successive harmonics 2{omega}, 3{omega}, etc., as a function of the intensity and of the frequency of the field and compare the results with those of first and second order perturbation theory.

Recamier, Jose; Mochan, W. Luis; Maytorena, Jesus A. [Centro de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, Cuernavaca, Morelos, 62251 (Mexico)

2005-08-15

28

Pattern Matching of Harmonic Vibrations in Nonlinearly Generated Acoustic Modes in Bovine Bone Samples  

NASA Astrophysics Data System (ADS)

Local probing of nonlinear generation of harmonic vibrations has been done on bone plate samples and the evaluation of the nonlinear term is derived from a limited number of cases of bovine thigh bones, that shows that a low level of nonlinearity is present in bone structures. This is consistent with the assumption that in low level nonlinear samples the distribution of harmonic vibrations matches the corresponding power distribution of the fundamental mode.

Alippi, A.; Biagioni, A.; Germano, M.; Passeri, D.

2008-06-01

29

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

PubMed

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

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

2010-04-01

30

Calculation of four-particle harmonic-oscillator transformation brackets  

NASA Astrophysics Data System (ADS)

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. 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.

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

2010-02-01

31

Vibrational structure theory: new vibrational wave function methods for calculation of anharmonic vibrational energies and vibrational contributions to molecular properties  

Microsoft Academic Search

A number of recently developed theoretical methods for the calculation of vibrational energies and wave functions are reviewed. Methods for constructing the appropriate quantum mechanical Hamilton operator are briefly described before reviewing a particular branch of theoretical methods for solving the nuclear Schrodinger equation. The main focus is on wave function methods using the vibrational self-consistent field (VSCF) as starting

Ove Christiansen

2007-01-01

32

Algebraic-matrix calculation of vibrational levels of triatomic molecules.  

PubMed

We introduce an accurate and efficient algebraic technique for the computation of the vibrational spectra of triatomic molecules, of both linear and bent equilibrium geometry. The full three-dimensional potential energy surface (PES), which can be based on entirely ab initio data, is parametrized as a product Morse-cosine expansion, expressed in bond angle internal coordinates, and includes explicit interactions among the local modes. We describe the stretching degrees of freedom in the framework of a Morse-type expansion on a suitable algebraic basis, which provides exact analytical expressions for the elements of a sparse Hamiltonian matrix. Likewise, we use a cosine power expansion on a spherical harmonics basis for the bending degree of freedom. The resulting matrix representation in the product space is very sparse, and vibrational levels and eigenfunctions can be obtained by efficient diagonalization techniques. We apply this method to carbonyl sulfide, hydrogen cyanide, water, and nitrogen dioxide. When we base our calculations on high-quality PESs tuned to the experimental data, the computed spectra are in very good agreement with the observed band origins. PMID:19419231

Sedivcová-Uhlíková, T; Abdullah, Hewa Y; Manini, Nicola

2009-05-28

33

Calculation of converged rovibrational energies and partition function for methane using vibrational-rotational configuration interaction.  

PubMed

The rovibration partition function of CH4 was calculated in the temperature range of 100-1000 K using well-converged energy levels that were calculated by vibrational-rotational configuration interaction using the Watson Hamiltonian for total angular momenta J = 0-50 and the MULTIMODE computer program. The configuration state functions are products of ground-state occupied and virtual modals obtained using the vibrational self-consistent field method. The Gilbert and Jordan potential energy surface was used for the calculations. The resulting partition function was used to test the harmonic oscillator approximation and the separable-rotation approximation. The harmonic oscillator, rigid-rotator approximation is in error by a factor of 2.3 at 300 K, but we also propose a separable-rotation approximation that is accurate within 2% from 100 to 1000 K. PMID:15260761

Chakraborty, Arindam; Truhlar, Donald G; Bowman, Joel M; Carter, Stuart

2004-08-01

34

Variational nodal perturbation calculations using simplified spherical harmonics  

SciTech Connect

The simplified spherical harmonics (SP{sub N}) method has been used as an approximation to the transport equation in a number of situations. Recently, the SP{sub N} method has been formulated within the framework of the variational nodal method (VNM). Implementation in the VARIANT code indicated that for many two and three dimensional problems, near P{sub N} accuracy can be obtained at a fraction of the Cost. Perturbation methods offer additional computational cost reduction for reactor core calculations and are indispensable for performing a variety of calculations including sensitivity studies and the breakdown by components of reactivity worths. Here, we extend the perturbation method developed for the VNM in the full P{sub N} approximation to treat simplified spherical harmonics. The change in reactivity predicted by both first order and exact perturbation theory using the SP{sub N} approximation is demonstrated for a benchmark problem and compared to diffusion and full P{sub N} estimates.

Laurin-Kovitz, K.; Palmiotti, G. [Argonne National Lab., IL (United States); Lewis, E.E. [Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering

1996-12-31

35

Investigation of temperature dependence of vibrational modes in a heme protein model compound using a self-consistent harmonic approximation  

NASA Astrophysics Data System (ADS)

Biologically significant heme protein model compounds are studied via normal mode analysis using both a conventional harmonic approach and a self consistent harmonic approximation (SCHA) approach in order to model anharmonicities. The SCHA calculation allows us to investigate and predict the temperature dependence of vibrational modes and bond amplitudes---something that no other theoretical method can accomplish without either prohibitive computational cost or unreasonable and non-physical results such as premature bond dissociation or conformational change. Considering temperature dependence of dynamics is important as most biological compounds perform their functions at temperatures (room temperature) much greater than those used during experimental spectroscopic measurements (usually liquid nitrogen or liquid helium temperatures). Our findings indicate that an increase in temperature will selectively amplify certain bond amplitudes in a, complex fashion that is not possible to predict from geometry, bond strengths or standard normal mode frequencies and amplitudes. In the end, intuition is in some sense verified by finding that the most amplified motions tend to be rotational motions of groups which are weakly bound and weakly coupled to the rest of the molecule---such as phenyl groups at the heme periphery. From both standard normal mode and SCHA calculations, density of states is obtained and compared with experimental density of states arising from a novel experimental technique called nuclear resonance vibrational spectroscopy (NRVS). Standard harmonic parameters are calculated and refined to match experimental data in Fe(OEP)Cl and Fe(TPP)NO(1-MeIm). Fe(TPP)NO(1-MeIm) is further modeled by use of a set of anharmonic interatomic potentials. Use of these potentials in a SCHA calculation allows prediction of the temperature dependence of the vibrational spectrum which compares favorably with experimental data.

Budarz, Timo Erkki Brian

36

Calculation of the vibrational spectrum of a sodium sulfate crystal  

Microsoft Academic Search

Based on model representations a calculation is made of the frequencies and forms of normal vibrations of a fragment of the\\u000a sodium sulfate crystal in the third phase. Calculated results are compared to experimental RS spectra.

M. V. Barashkov; A. I. Komyak; S. N. Shashkov

1999-01-01

37

Study of the effects of cubic nonlinear damping on vibration isolations using Harmonic Balance Method  

Microsoft Academic Search

In the present study, Harmonic Balance Method (HBM) is applied to investigate the performance of passive vibration isolators with cubic nonlinear damping. The results reveal that introducing either cubic nonlinear damping or linear damping could significantly reduce both the displacement transmissibility and the force transmissibility of the isolators over the resonance region. However, at the non-resonance region where frequency is

Z. K. Peng; G. Meng; Z. Q Lang; W. M. Zhang; F. L. Chu

38

Polynomial and harmonic differential quadrature methods for free vibration of variable thickness thick skew plates  

Microsoft Academic Search

An examination of the accuracy and convergence behaviors of polynomial basis function differential quadrature (PDQ) and harmonic basis function differential quadrature (HDQ) for free vibration analysis of variable thickness thick skew plates will be carried out. The plate governing equations are based on the first-order shear deformation theory including the effects of rotary inertia. Arbitrary thickness variations will be assumed

P. Malekzadeh; G. Karami

2005-01-01

39

Optimal control of selective vibrational excitation in harmonic linear chain molecules  

Microsoft Academic Search

A formalism for designing an optical field for selective vibrational excitation in linear harmonic chain molecules is presented based on optimal control theory. The optimizing functional producing the field designs is flexible to allow for the imposition of desirable laboratory and theoretical constraints. The designed optimal fields, which successfully lead to local bond excitations, exhibit complex structure on the time

Shenghua Shi; Andrea Woody; Herschel Rabitz

1988-01-01

40

A systematic study on the basis set dependence of the Hartree-Fock, MP2 and CIS harmonic force fields and vibrational frequencies of formaldehyde in comparison with the experimental results  

Microsoft Academic Search

The aim of this work was to find the limits of the vibrational frequency calculations by ab initio methods, in the framework of the harmonic frequency model and so find the possibility of eliminating the scaling of force constants.Therefore the efficiency of the different ab initio methods and basis sets were investigated from the point of view of vibrational frequency

Ferenc Billes

1995-01-01

41

Production engineering programs. 1. Exponential, harmonic declines programmed for calculators  

SciTech Connect

Production and reservoir engineers can use simplified programs developed for the HP-41C calculator to predict several different types of well behavior. Five Hewlett-Packard subroutines simplify the program design and make the programs useful with or without a printer. The program described in this series analyzes and forecasts exponential and harmonic declines. The decline curves can be defined in several ways and extrapolated to a future rate, time, or cumulative production. The program can handle various units of measurement and give annual forecasts as well.

Meehan, D.N.

1980-05-26

42

Molecular structure, vibrational, UV and NBO analysis of 4-chloro-7-nitrobenzofurazan by DFT calculations.  

PubMed

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of 4-chloro-7-nitrobenzofurazan (NBD-Chloride). The FT-IR (400-4000 cm(-1)) and FT-Raman spectra (50-4000 cm(-1)) of NBD-Chloride were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of NBD-Chloride in the ground-state have been calculated by using the density functional B3LYP method with 6-311++G (d, p) as higher basis set. The energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) result in DMSO and CDCl3 solvents complements with each other. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which show good agreement with observed spectra. PMID:21571581

Kurt, M; Babu, P Chinna; Sundaraganesan, N; Cinar, M; Karabacak, M

2011-04-22

43

An ab initio study of the in-plane harmonic force fields and fundamental vibration frequencies of cis- and trans-1,3-butadiene  

NASA Astrophysics Data System (ADS)

The structure, in-plane force field, and fundamental vibration frequencies of trans- and cis-1,3-butadiene are calculated ab initio using the 4-31G basis set. Using a scaling procedure based on computational results from smaller molecules, the vibration frequencies for the trans-conformer calculated from the ab initio force constant matrix are found on average to be within 2.2% of the experimental values ``harmonized'' according to Dennison's rule. The values predicted for the cis-conformer, for which experimental spectroscopic data are only now becoming available, should facilitate the complete in-plane assignment of fundamentals in the near future.

Bock, Charles W.; Trachtman, Mendel; George, Philip

1980-11-01

44

Intermolecular vibrations in hydrophobic amino Acid crystals: experiments and calculations.  

PubMed

Intermolecular vibrations of amino acid crystals occur in the THz, or far-infrared, region of the electromagnetic spectrum. We have measured the THz and Raman spectra of dl-leucine as well as two polymorphs of dl-valine, the spectroscopic properties of which have not previously been compared. Theoretical modeling of intermolecular vibrations in hydrophobic amino acids is challenging because the van der Waals interactions between molecules are not accounted for in standard density functional theory. Therefore, to calculate the vibrational modes, we used a recently developed approach that includes these nonlocal electron correlation forces. We discuss methods for comparing results from different theoretical models using metrics other than calculated vibrational frequency and intensity, and we also report a new approach enabling concise comparison of vibrational modes that involve complicated mixtures of inter- and intramolecular displacements. PMID:23931283

Williams, Michael R C; Aschaffenburg, Daniel J; Ofori-Okai, Benjamin K; Schmuttenmaer, Charles A

2013-08-28

45

Harmonic and Random Vibration Durability of SAC305 and Sn37Pb Solder Alloys  

Microsoft Academic Search

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

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

2010-01-01

46

Rotor blade-vortex interaction noise reduction and vibration using higher harmonic control  

Microsoft Academic Search

The use of higher harmonic control (HHC) of blade pitch to reduce blade-vortex interaction (BVI) noise is examined by means of a rotor acoustic test. A dynamically scaled, four-bladed, articulated rotor model was tested in a heavy gas (Freon-12) medium. Acoustic and vibration measurements were made for a large range of matched flight conditions where prescribed (open loop) HHC pitch

Thomas F. Brooks; Earl R. Booth Jr.

1990-01-01

47

Calculation of Vibrational Spectra of p-Ethylbenzenesulfonic Acid Hydrates  

NASA Astrophysics Data System (ADS)

Quantum-chemical calculations of vibrational spectra of the sulfonated ion-exchanger model p-ethylbenzenesulfonic acid hydrated by 1-10 water molecules and its dimer were calculated by the non-empirical SCF MO LCAO method with the 6-31G(d) basis set. The calculated results were compared with experimental IR and Raman spectra of sulfonated ion exchangers. The infl uence of hydration on the vibrational frequencies of functional groups in the ion exchangers was analyzed. It was shown that the sulfonic acid was completely dissociated if three and more water molecules per functional group were present. Bands near 1130 cm-1 were due to S-O-H bending vibrations in the absence of water molecules and C-S-O-H3O combination vibrations with 3-6 water molecules per sulfonic acid.

Zelenkovskii, V. M.; Bezyazychnaya, T. V.; Soldatov, V. S.

2013-09-01

48

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

NASA Astrophysics Data System (ADS)

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.

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

2010-09-01

49

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

PubMed

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 (1)H and (13)C NMR chemical shifts in DMSO solution and calculated GIAO shielding tensors were found. PMID:20621610

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

2010-05-24

50

Trial wave functions for the calculation of vibrational states of molecules using quantum Monte Carlo  

NASA Astrophysics Data System (ADS)

In this article we test three kinds of trial wave functions for the calculation of vibrational excited states of molecules using quantum Monte Carlo. We begin our study with the basis set originally used by Bernu and co-workers and further modified by Acioli and Soares Neto. The second set tested was the simplified Morse oscillator-like with harmonic coupling (SMOL-HC) proposed by Brown et al. to study the vibrational spectra of C3. Finally we proposed a third basis set, based on the previous two. This basis set keeps the anharmonicity of the SMOL-HC basis but with well conditioned Hamiltonian and overlap matrices. The calculations were performed in the H2, H3+, and H2O molecules. The results indicate that the basis sets proposed in this work yield more accurate results with a smaller number of basis functions.

da Silva, Washington B.; Acioli, Paulo H.

2001-06-01

51

Nonlinear vibration of viscoelastic sandwich beams by the harmonic balance and finite element methods  

NASA Astrophysics Data System (ADS)

This paper deals with geometrically nonlinear vibrations of sandwich beams with viscoelastic materials. For this purpose, a new finite element formulation has been developed, in which a zig-zag model is used to describe the displacement field. The viscoelastic behaviour is handled by using hereditary integrals and their relationships with complex moduli. An efficient solution procedure based on the harmonic balance method is also developed. To demonstrate its abilities, various problems of nonlinear vibrations of sandwich beams are considered. First, the results derived from the proposed approach are compared with those of nonlinear dynamic analyses using direct time integration and to experimental data. Then, the influence of the vibration amplitude on the damping properties of sandwich beams is investigated. The effect of an initial axial strain is also examined.

Jacques, N.; Daya, E. M.; Potier-Ferry, M.

2010-09-01

52

Symmetric variational formulation of harmonic vibrations problem by coupling primal and dual principles. Application to fluid-structure coupled systems  

NASA Astrophysics Data System (ADS)

A methodology is presented for the coupling of a primal principle and an indirect dual principle leading to a symmetric variational formulation for the harmonic vibrations problem. The symmetric formulation governing the elasto-acoustic vibration problems and more generally fluid-structure coupling are found directly.

Ohayon, R.

1980-01-01

53

Non-Linear vibrations and chaos in harmonically excited rectangular plates with one-to-one internal resonance  

Microsoft Academic Search

Nonlinear flexural vibrations of a rectangular plate with uniform stretching are studied for the case when it is harmonically excited with forces acting normal to the midplane of the plate. The physical phenomena of interest here arise when the plate has two distinct linear modes of vibration with nearly the same natural frequency. It is shown that, depending on the

S. I. Chang; A. K. Bajaj; C. M. Krousgrill

1993-01-01

54

Ab initio calculation of the rotational spectrum of methane vibrational ground state.  

PubMed

In a previous article we have introduced an alternative perturbation scheme to the traditional one starting from the harmonic oscillator, rigid rotator Hamiltonian, to find approximate solutions of the spectral problem for rotation-vibration molecular Hamiltonians. The convergence of our method for the methane vibrational ground state rotational energy levels was quicker than that of the traditional method, as expected, and our predictions were quantitative. In this second article, we study the convergence of the ab initio calculation of effective dipole moments for methane within the same theoretical frame. The first order of perturbation when applied to the electric dipole moment operator of a spherical top gives the expression used in previous spectroscopic studies. Higher orders of perturbation give corrections corresponding to higher centrifugal distortion contributions and are calculated accurately for the first time. Two potential energy surfaces of the literature have been used for solving the anharmonic vibrational problem by means of the vibrational mean field configuration interaction approach. Two corresponding dipole moment surfaces were calculated in this work at a high level of theory. The predicted intensities agree better with recent experimental values than their empirical fit. This suggests that our ab initio dipole moment surface and effective dipole moment operator are both highly accurate. PMID:22583232

Cassam-Chenaď, P; Liévin, J

2012-05-01

55

Nonlinear vibration of a curved beam under uniform base harmonic excitation with quadratic and cubic nonlinearities  

NASA Astrophysics Data System (ADS)

This paper presents nonlinear vibration analysis of a curved beam subject to uniform base harmonic excitation with both quadratic and cubic nonlinearities. The Galerkin method is employed to discretize the governing equations. A high-dimensional model that can take nonlinear model coupling into account is derived, and the incremental harmonic balance (IHB) method is employed to obtain the steady-state response of the curved beam. The cases investigated include softening stiffness, hardening stiffness and modal energy transfer. The stability of the periodic solutions for given parameters is determined by the multi-variable Floquet theory using Hsu's method. Particular attention is paid to the anti-symmetric response with and without excitation, as the excitation frequency is close to the first and third natural frequencies of the system. The results obtained with the IHB method compare very well with those obtained via numerical integration.

Huang, J. L.; Su, R. K. L.; Lee, Y. Y.; Chen, S. H.

2011-10-01

56

Characterization of vibrational wave packets by core-level high-harmonic transient absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The ground-state vibrational wave packet produced by strong-field ionization of Br2 is characterized by femtosecond high-harmonic transient absorption spectroscopy. Vibrational motion is observed in time by a change in the 3d core-level transition energy with bond length 0.14 eV/pm to higher energies at shorter bond lengths. The wave packet has the expected period of 104 fs for the predominant v0v1 vibrational quantum beat, which is prepared near the outer turning point with a phase of 0.21?ą0.05? due to the preferential ionization at short bond lengths. Simultaneous observation of a wave packet on the Br2+2?g,3/2 ground state, prepared at the equilibrium bond distance of the ion, confirms preferential ionization near the inner turning point of the neutral. The Br2 ground-state wave packet has a degree of coherence ranging between 0.19 and 0.24, where unity is perfect coherence. The results utilize the sensitivity of core-level transient absorption spectroscopy to bond length and charge state, providing a means to analyze the formation and evolution of vibrational wave packets.

Hosler, Erik R.; Leone, Stephen R.

2013-08-01

57

Geometrical Method for the Calculation of Spherical Harmonics up to an Arbitrary Degree and Order  

NASA Astrophysics Data System (ADS)

We introduce a novel method for the computation and rotation of spherical harmonics, Legendre polynomials and associated Legendre functions without making use of recursive relations. This novel geometrical approach allows calculation of spherical harmonics without any numerical instability up to an arbitrary degree and order, i.e. up to a degree and order 1e6 and beyond. It is shown, that spherical harmonics can be treated as vectors in Hilbert hyperspace leading to the unitary hermitian rotation matrices with geometric properties.

Svehla, D.

2009-12-01

58

Super- and sub-harmonic response calculations for a torsional system with clearance nonlinearity using the harmonic balance method  

NASA Astrophysics Data System (ADS)

This article presents a new multi-term harmonic balance method (HBM) for nonlinear frequency response calculations of a torsional sub-system containing a clearance type nonlinearity. The ability of the simplified subsystem to capture the salient behavior of the larger system is verified by the comparison of results to experimental data. Unlike previous analytical and numerical methods, the proposed HBM includes adaptive arc-length continuation and stability calculation capabilities to find periodic solutions in multi-valued nonlinear frequency response regimes as well as to improve convergence. Essential steps of the proposed HBM calculations are introduced, and it is validated by comparing time and frequency domain predictions with those yielded by numerical solutions, experimental studies, or analog simulations for several examples. Then, nonlinear frequency response characteristics of an oscillator with clearance nonlinearity are examined with focus on super- and sub-harmonics. We also explore some issues that are not fully resolved in the literature. For instance, the effect of mean operating point is examined for ?=0 and ?=0.18-0.25 cases where ? is the stiffness ratio of the piecewise-linear elastic function. In addition, the number of harmonic terms that must be included in the HBM response calculations, given sinusoidal excitation, has been investigated. Finally, some simple analytical predictions for super and sub-harmonic resonances are presented.

Kim, T. C.; Rook, T. E.; Singh, R.

2005-03-01

59

Accurate calculation of high harmonics generated by relativistic Thomson scattering  

Microsoft Academic Search

The recent emergence of the field of ultraintense laser pulses, corresponding to beam intensities higher than 1018 W cm-2, brings about the problem of the high harmonic generation (HHG) by the relativistic Thomson scattering of the electromagnetic radiation by free electrons. Starting from the equations of the relativistic motion of the electron in the electromagnetic field, we give an exact

Alexandru Popa

2008-01-01

60

Attenuation of Harmonic Rotor Vibration in a Cage Rotor Induction Machine by a Self-Bearing Force Actuator  

Microsoft Academic Search

In this paper, attenuation of flexural rotor vibration in electrical machines is considered. In order to generate force on the machine rotor, an electromagnetic actuator based on self-bearing machine working principle is examined. A control method for attenuating harmonic rotor vibration components is applied in a 30 kW two-pole cage induction machine. The machine is equipped with a four-pole supplementary

Antti Laiho; Anssi Sinervo; Juha Orivuori; Kari Tammi; Antero Arkkio; Kai Zenger

2009-01-01

61

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

SciTech Connect

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.

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

62

Calculations of vibration-rotation energy levels of HD+  

Microsoft Academic Search

An artificial-channels scattering method [M. Shapiro and G. G. Balint-Kurti, J. Chem. Phys. 71, 1461 (1979)] is used with a transformed Hamiltonian [R. E. Moss and I. A. Sadler, Molec. Phys. 66, 591 (1989)] to calculate the energies of vibration-rotation levels for the ground electronic state of HD+. All nonadiabatic effects, except for part of the coupling of rotational and

G. G. Balint-Kurti; R. E. Moss; I. A. Sadler; M. Shapiro

1990-01-01

63

Rotor blade-vortex interaction noise reduction and vibration using higher harmonic control  

NASA Astrophysics Data System (ADS)

The use of higher harmonic control (HHC) of blade pitch to reduce blade-vortex interaction (BVI) noise is examined by means of a rotor acoustic test. A dynamically scaled, four-bladed, articulated rotor model was tested in a heavy gas (Freon-12) medium. Acoustic and vibration measurements were made for a large range of matched flight conditions where prescribed (open loop) HHC pitch schedules were superimposed on the normal (baseline) collective and cyclic trim pitch. A novel sound power measurement technique was developed to take advantage of the reverberance in the hard walled tunnel. Quantitative sound power results are presented for a 4/rev (4P) collective pitch HHC. By comparing the results using 4P HHC to corresponding baseline (no HHC) conditions, significant midfrequency noise reductions of 5-6 dB are found for low-speed descent conditions where BVI is most intense. For other flight conditions, noise is found to increase with the use of HHC. LF loading noise, as well as fixed and rotating frame vibration levels, show increased levels.

Brooks, Thomas F.; Booth, Earl R., Jr.

1990-09-01

64

Vibrational subsystem analysis: A method for probing free energies and correlations in the harmonic limit  

PubMed Central

A new vibrational subsystem analysis (VSA) method is presented for coupling global motion to a local subsystem while including the inertial effects of the environment. The premise of the VSA method is a partitioning of a system into a smaller region of interest and a usually larger part referred to as environment. This method allows the investigation of local-global coupling, a more accurate estimation of vibrational free energy contribution for parts of a large system, and the elimination of the “tip effect” in elastic network model calculations. Additionally, the VSA method can be used as a probe of specific degrees of freedom that may contribute to free energy differences. The VSA approach can be employed in many ways, but it will likely be most useful for estimating activation free energies in QM?MM reaction path calculations. Four examples are presented to demonstrate the utility of this method.

Woodcock, H. Lee; Zheng, Wenjun; Ghysels, An; Shao, Yihan; Kong, Jing; Brooks, Bernard R.

2008-01-01

65

Vibrational subsystem analysis: A method for probing free energies and correlations in the harmonic limit  

NASA Astrophysics Data System (ADS)

A new vibrational subsystem analysis (VSA) method is presented for coupling global motion to a local subsystem while including the inertial effects of the environment. The premise of the VSA method is a partitioning of a system into a smaller region of interest and a usually larger part referred to as environment. This method allows the investigation of local-global coupling, a more accurate estimation of vibrational free energy contribution for parts of a large system, and the elimination of the ``tip effect'' in elastic network model calculations. Additionally, the VSA method can be used as a probe of specific degrees of freedom that may contribute to free energy differences. The VSA approach can be employed in many ways, but it will likely be most useful for estimating activation free energies in QM/MM reaction path calculations. Four examples are presented to demonstrate the utility of this method.

Woodcock, H. Lee; Zheng, Wenjun; Ghysels, An; Shao, Yihan; Kong, Jing; Brooks, Bernard R.

2008-12-01

66

Vibrational spectroscopic studies and DFT calculations of 4-bromo-o-xylene  

NASA Astrophysics Data System (ADS)

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of 4-bromo-o-xylene (BOX). The FT-IR (400-4000 cm-1) and FT-Raman spectra (50-3500 cm-1) of BOX were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of BOX in the ground state have been calculated by using the density functional B3LYP method with 6-311++G(d,p)/6-311+G(d,p) higher basis sets. The energy and oscillator strength are calculated by time-dependent density functional theory (TD-DFT). To determine conformational flexibility, molecular energy profile of BOX was obtained by B3LYP method with 6-311++G(d,p) basis set with respect to selected degree of torsional freedom, which gives three stable conformers. Besides, molecular electrostatic potential (MEP), non-linear properties and NMR analysis were performed at DFT level of theory.

Arivazhagan, M.; Meenakshi, R.

67

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

National Technical Information Service (NTIS)

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 ...

J. R. Johler R. L. Lewis

1968-01-01

68

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

Microsoft Academic Search

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

J. Ralph Johler; Richard L. Lewis

1969-01-01

69

Calculation of thermo-optical distortions of some nonlinear crystals during second-harmonic generation  

SciTech Connect

Numerical calculations are reported of thermooptical distortions of nonlinear ADP, LiNbO{sub 3}, KDP nonlinear crystals used in second-harmonic generation. The elasto-optical effect is taken into account. The calculations are made for crystalline samples in the form of circular cylinders in which a steady-state parabolic temperature field is established. (nonlinear optical phenomena and devices)

Dmitriev, Valentin G [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation); Yur'ev, Yu V [Moscow Physicotechnical Institute (State University), Moscow (Russian Federation)

1998-11-30

70

Calculation of dipole moment functions with density functional theory: application to vibrational band intensities  

NASA Astrophysics Data System (ADS)

We have calculated fundamental and overtone XH stretching vibrational band intensities for H2O, benzene, cyclohexane,1,3-butadiene, and HCN. The band intensities were calculated with a simple harmonically coupled anharmonic oscillator local mode model and a series expanded dipole moment function. The dipole moment functions were obtained from local, non-local and hybrid density functional theory calculations with basis sets ranging from 6-31G(d) to 6-311 G(3df,3pd). The calculated band intensities have been compared with intensities calculated with conventional ab initio methods and with experimental results. Compared with conventional correlated ab initio methods, a carefully chosen density functional method and basis set seems to give better fundamental and overtone intensities with far less resources used. We have found that the density functional methods appear to be less sensitive to the choice of basis set, with little difference between the results obtained with a non-local or hybrid density functional method.

Kjaergaard, Henrik G.

71

Calculation of eccentricity harmonics of the air-gap flux density in induction Machines by impulse method  

Microsoft Academic Search

The rotor eccentricity creates extra harmonics into the flux-density distribution in the air gap. Together with the fundamental field-component, these harmonics create the total force acting between the stator and eccentric rotor. The paper presents a new application of the impulse method, which enables the calculation of the harmonics of the flux density distribution when the rotor is eccentric. The

Asmo Tenhunen

2005-01-01

72

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

73

Structures, electron affinities, and harmonic vibrational frequencies of the simplest alkyl peroxyl radicals and their anions.  

PubMed

The molecular structures and electron affinities of the R-OO/R-OO(-) (R = CH3, C2H5, n-C3H7, n-C4H9, n-C5H11, i-C3H7, t-C4H9) species have been determined using seven different density functional or hybrid Hartree-Fock density functional methods. The basis set used in this work is of double-zeta plus polarization quality with additional diffuse s-type and p-type functions, denoted DZP++. The geometries are fully optimized with each density functional theory method. Harmonic vibrational frequencies were found to be within 3.1% of available experimental values for most functionals. Two different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity and the vertical detachment energy. The most reliable adiabatic electron affinities obtained at the DZP++ BP86 level of theory are 1.150 (CH3OO), 1.124 (C2H5OO), 1.146 (n-C3H7OO), 1.173 (n-C4H9OO), 1.184 (n-C5H11OO), 1.145 (i-C3H7OO), and 1.114 eV (t-C4H9OO). Compared with the experimental values, the average absolute error of the BPW91 method is 0.05 eV. PMID:18597444

Xu, Wenguo; Lu, Gaoyu

2008-07-03

74

Molecular structure and vibrational spectra of o-chlorotoluene, m-chlorotoluene, and p-chlorotoluene by ab initio HF and DFT calculations  

NASA Astrophysics Data System (ADS)

In this work, experimental and theoretical study on the molecular structure and the vibrational spectra of o-chlorotoluene (OCT), m-chlorotoluene (MCT) and p-chlorotoluene (PCT) are presented. The vibrational frequencies of these compounds were obtained theoretically by ab initio HF and DFT/B3LYP calculations employing the standard 6-311++G(d,p) basis set for optimized geometries and were compared with Fourier transform infrared (FTIR) in the region of 400-4000 cm -1 and with Raman spectra in the region of 100-4000 cm -1. Complete vibrational assignment, analysis and correlation of the fundamental modes for these compounds have been carried out. The vibrational harmonic frequencies were scaled using scale factors, yielding a good agreement between the experimentally recorded and the theoretically calculated values.

Wang, Jidong; Ren, Mingmin; Wang, Shui; Qu, Yixin

2011-03-01

75

Molecular structure and vibrational study of diprotonated guanazolium using DFT calculations and FT-IR and FT-Raman spectroscopies.  

PubMed

The purpose of this manuscript is to discuss our investigations of diprotonated guanazolium chloride using vibrational spectroscopy and quantum chemical methods. The solid phase FT-IR and FT-Raman spectra were recorded in the regions 4000-400cm(-1) and 3600-50cm(-1) respectively, and the band assignments were supported by deuteration effects. Different sites of diprotonation have been theoretically examined at the B3LYP/6-31G level. The results of energy calculations show that the diprotonation process occurs with the two pyridine-like nitrogen N2 and N4 of the triazole ring. The molecular structure, harmonic vibrational wave numbers, infrared intensities and Raman activities were calculated for this form by DFT/B3LYP methods, using a 6-31G basis set. Both the optimized geometries and the theoretical and experimental spectra for diprotonated guanazolium under a stable form are compared with theoretical and experimental data of the neutral molecule reported in our previous work. This comparison reveals that the diprotonation occurs on the triazolic nucleus, and provide information about the hydrogen bonding in the crystal. The scaled vibrational wave number values of the diprotonated form are in close agreement with the experimental data. The normal vibrations were characterized in terms of potential energy distribution (PED) using the VEDA 4 program. PMID:22925973

Guennoun, L; Zaydoun, S; El Jastimi, J; Marakchi, K; Komiha, N; Kabbaj, O K; El Hajji, A; Guédira, F

2012-08-01

76

Vibrational mode analysis and heat capacity calculation of K2SiSi3O9-wadeite  

NASA Astrophysics Data System (ADS)

The phonon dispersions and vibrational density of state (VDoS) of the K2SiSi3O9-wadeite (Wd) have been calculated by the first-principles method using density functional perturbation theory. The vibrational frequencies at the Brillouin zone center are in good correspondence with the Raman and infrared experimental data. The calculated VDoS was then used in conjunction with a quasi-harmonic approximation to compute the isobaric heat capacity (C P ) and vibrational entropy (S_{298}0), yielding C P (T) = 469.4(6) - 2.90(2) × 103 T -0.5 - 9.5(2) × 106 T -2 + 1.36(3) × 109 T -3 for the T range of 298-1,000 K and S_{298}0 = 250.4 J mol-1 K-1. In comparison, these thermodynamic properties were calculated by a second method, the classic Kieffer's lattice vibrational model. On the basis of the vibrational mode analysis facilitated by the first-principles simulation result, we developed a new Kieffer's model for the Wd phase. This new Kieffer's model yielded C P (T) = 475.9(6) - 3.15(2) × 103 T -0.5 - 8.8(2) × 106 T -2 + 1.31(3) × 109 T -3 for the T range of 298-1,000 K and S_{298}0 = 249.5(40) J mol-1 K-1, which are in good agreement both with the results from our first method containing the component of the first-principles calculation and with some calorimetric measurements in the literature.

Chang, Linlin; Liu, Xi; Liu, Hong; Kojitani, Hiroshi; Wang, Sicheng

2013-04-01

77

Generation of High-Frequency Harmonics in the Case of Large-Amplitude Vibrations of a Gas in a Closed Tube  

Microsoft Academic Search

Based on the model of a viscous compressible heat-conducting gas, the author investigates numerically the vibrations of a gas column in a closed tube in excitation by a flat piston that moves according to a harmonic law with an amplitude comparable to the resonator length. Consideration is given to the process of transformation of the mode and frequency of vibrations

A. L. Tukmakov

2001-01-01

78

ON THE USE OF SCHROEDER PHASED HARMONIC SEQUENCES IN MULTI-FREQUENCY VIBRATION CONTROL OF FLEXIBLE ROTOR\\/MAGNETIC BEARING SYSTEMS  

Microsoft Academic Search

Control strategies based on synchronous vibration cancellation have been successfully applied to rotor- bearing systems incorporating magnetic bearings. In this paper, such a control strategy is extended to provide attenuation of sub and super-harmonic vibration components resulting from multi-frequency excitation of the system. System identification is achieved using test signals applied through the magnetic bearings that consist of multiple frequency

Mehmet N. Sahinkaya; Matthew O. T. Cole; Clifford R. Burrows

79

Ab initio calculations of vibrational frequencies and infrared intensities for global warning potential of CFC substitutes. CFâCHâF (HFC134a)  

Microsoft Academic Search

We have investigated the feasibility of using ab initio molecular orbital methods for predicting the global warming potential of the proposed chlorofluorocarbon (CFC) substitute CFâCHâF, HFC-134a. Various levels of theory and basis sets were used to optimize geometry and calculate harmonic vibrational frequencies and infrared intensities for the molecule using the GAUSSIAN 92 software package. In attempting to assess the

Stella Papasavva; Stephanie Tai; Amy Esslinger; Karl H. Illinger; Jonathan E. Kenny

1995-01-01

80

“Troublesome” Vibrations of Aromatic Molecules in Second-Order Möller?Plesset and Density Functional Theory Calculations:  Infrared Spectra of Phenol and Phenol-OD Revisited  

Microsoft Academic Search

The infrared spectra of phenol and phenol-OD are thoroughly reinvestigated, to resolve the contradictory assignment of some vibrations. The harmonic frequencies, integrated IR intensities, and potential energy distribution (PED) have been calculated by the B3LYP method with the 6-311++G(df,pd) basis set. The Fourier transform infrared (FT-IR) spectra of phenol and phenol-OD have been measured in carbon tetrachloride and cyclohexane solutions,

Danuta Michalska; Wiktor Zierkiewicz; Dariusz C. Bienko; Walter Wojciechowski; Thérčse Zeegers-Huyskens

2001-01-01

81

Rapid calculations of time-harmonic nearfield pressures produced by rectangular pistons.  

PubMed

A rapid method for calculating the nearfield pressure distribution generated by a rectangular piston is derived for time-harmonic excitations. This rapid approach improves the numerical performance relative to the impulse response with an equivalent integral expression that removes the numerical singularities caused by inverse trigonometric functions. The resulting errors are demonstrated in pressure field calculations using the time-harmonic impulse response solution for a rectangular source 5 wavelengths wide by 7.5 wavelengths high. Simulations using this source geometry show that the rapid method eliminates the singularities introduced by the impulse response. The results of pressure field computations are then evaluated in terms of relative errors and computational speeds. The results show that, when the same number of Gauss abscissas are applied to both approaches for time-harmonic pressure field calculations, the rapid method is consistently faster than the impulse response, and the rapid method consistently produces smaller maximum errors than the impulse response. For specified maximum error values of 10% and 1%, the rapid method is 2.6 times faster than the impulse response for pressure field calculations performed on a 61 by 101 point grid. The rapid approach achieves even greater reductions in the computation time for smaller errors and larger grids. PMID:15139602

McGough, Robert J

2004-05-01

82

Calculation of harmonic generation during the multiphoton ionization of the hydrogen atom  

SciTech Connect

The response of a hydrogen atom to an intense nonresonant laser field is investigated by direct numerical solution of the time-dependent Schroedinger equation. This calculation is nonperturbative and does not involve the eigenstates of the field-free atom. An ionization rate for three-photon ionization is calculated and found to be in excellent agreement with previous values. The time-dependent electric dipole moment is calculated; its Fourier transform yields the spectrum of scattered light. Odd-order harmonic peaks through at least the 25th order are present in the spectrum.

DeVries, P.L. (Department of Physics, Miami University, Oxford, Ohio 45056 (USA))

1990-04-01

83

A simplified spherical harmonic method for coupled electron-photon transport calculations  

Microsoft Academic Search

In this thesis we have developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. We have performed a first time Fourier analysis of the source iteration scheme and the P⁠diffusion synthetic acceleration (DSA) scheme applied to

Josef

1996-01-01

84

Calculation of the convex roof for an open entangled harmonic oscillator system  

SciTech Connect

We explicitly calculate the time dependence of entanglement via the convex roof extension for a system of noninteracting harmonic oscillators. These oscillators interact only indirectly with each other by way of a zero-temperature bath. The initial state of the oscillators is taken to be that of an entangled Schroedinger-cat state. This type of initial condition leads to superexponential decay of the entanglement when the initial state has the same symmetry as the interaction Hamiltonian.

Landau, Mayer A.; Stroud, C. R. Jr. [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2010-05-15

85

Molecular structure and vibrational analysis of 3-Ethylpyridine using ab initio HF and density functional theory (B3LYP) calculations.  

PubMed

The FT-Raman and FT-IR spectra for 3-Ethylpyridine (3-EP) have been recorded in the region 4000-100 cm(-1) and compared with the harmonic vibrational frequencies calculated using HF/DFT (B3LYP) method by employing 6-31G(d,p) and 6-311++G(d,p) basis set with appropriate scale factors. IR intensities and Raman activities are also calculated by HF and DFT (B3LYP) methods. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values of some substituted benzene. The experimental geometrical parameters show satisfactory agreement with the theoretical prediction from HF and DFT. 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. Some of the vibrational frequencies of the pyridine are effected upon profusely with the C2H5 substitutions in comparison to pyridine and these differences are interpreted. PMID:21183400

Shakila, G; Periandy, S; Ramalingam, S

2010-12-10

86

Lattice Monte Carlo calculations for unitary fermions in a harmonic trap  

SciTech Connect

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.

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

87

Monochromator harmonic content measurements and calculations at energies above 20 keV  

SciTech Connect

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.

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

1991-01-01

88

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

NASA Astrophysics Data System (ADS)

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.

Balachandran, V.; Parimala, K.

89

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

PubMed

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. PMID:22542395

Balachandran, V; Parimala, K

2012-04-06

90

Variational Calculations for the Spectrum of Finite Bosons in Harmonic Potentials  

NASA Astrophysics Data System (ADS)

Using both the Gaussian and Fetter's variational calculations for the N-body ground-state wavefunction of the trapped Bose-Einstein condensate, we give explicit analytic formulae for the spectrum of finite bosons in harmonic potentials based on the corrected sum rules and generalized virial identities. We compare the low-lying excitation spectra among the Gaussian and Fetter's variational calculations and the exact numerical results. The Gaussian approximation has the simplest reasonable results, valid for Nrightarrowinfty and high-lying excitations.

Ma, Yong-Li; Chen, Zhong-Zhou

2003-09-01

91

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

92

Benchmark calculations of first principles rotational and ro-vibrational line strenghts  

Microsoft Academic Search

Benchmark first principles calculations of the pure rotational and ro-vibrational transition frequencies and line strengths are presented, using two independent program suites. Both sets of calculations were performed using the same potential energy and dipole surfaces. Our example calculations use recently calculated surfaces for H2S which have been shown to give good agreement with experimental data. The results, which show

Stuart Carter; Pavel Rosmus; Nicholas C. Handy; Steven Miller; Jonathan Tennyson; Brian T. Sutcliffe

1989-01-01

93

A comparison of calculations and measurements of the field harmonics as a function of current in the SSC dipole magnets  

SciTech Connect

A large number of short and long superconducting dipole magnets for the Superconducting Super Collider (SSC) have been constructed and measured for their magnetic field properties at Brookhaven National Laboratory (BNL). In this paper we compare the calculations and measurements for the variation of field harmonics as a function of current in 40 mm aperture and 50 mm aperture dipole magnets. The primary purpose of this paper is to examine the iron saturation effects on the field harmonics. The field harmonics also change due to the persistent current in the superconducting wires and due to the deformation of the coil shape because of Lorentz forces. We discuss the variation in the sextupole harmonics (b{sub 2}) with current and explain the differences between the calculations and measurements. We also discuss the skew quadrupole harmonic at high field in the long dipole magnets. 3 refs., 3 figs., 1 tab.

Gupta, R.C.; Cottingham, J.G.; Kahn, S.A.; Morgan, G.H.; Wanderer, P.

1991-01-01

94

Molecular structure and vibrational Raman and infrared spectra of bromochlorofluoromethane and its silicon and germanium analogs: quantum-mechanical DFT and MP2 calculations  

NASA Astrophysics Data System (ADS)

DFT(B3LYP) and MP2 calculations with the 6-311G(2d, 2p)-type basis set have been carried out for the prediction of molecular parameters (bond distances, bond angles, rotational constants, and dipole moments) and vibrational Raman and infrared spectra (harmonic wavenumbers, absolute intensities, Raman scattering activities, and depolarization ratios) of bromochlorofluoromethane (HCBrClF) and its silicon and germanium analogs (HSiBrClF and HGeBrClF). The predicted geometry and vibrational Raman and inftared spectra of HCBrClF agree well with the available experimental data for this molecule and their deuterated derivatives. This agreement allows one to believe that the predicted molecular parameters and vibrational spectra of HSiBrClF, HGeBrClF, and their deuterated derivatives will guide their future experimental studies.

Kwiatkowski, Józef S.; Leszczynski, Jerzy; Venkatraman, Ramaiyer

2000-12-01

95

Calculating Ro-Vibrational Spectra Using AN Eckart Frame  

NASA Astrophysics Data System (ADS)

Using normal coordinates and an Eckart molecule-fixed frame it is possible, for some molecules, to compute ro-vibrational spectra with either perturbation theory or variational methods. A compact normal coordinate Eckart kinetic energy operator (KEO) has been known for decades. The Eckart frame minimises Coriolis coupling and thereby reduces the number of basis functions required to achieve converged energy levels. It, however, is almost always used with normal coordinates which are poorly suited to the description of large amplitude vibrations. For molecules with large amplitude motion, it is common to use, as vibrational coordinates, polar coordinates associated with a set of vectors specifying the position of the atoms of the molecule. The vectors may be bond vectors, Jacobi vectors, Radau vectors etc. It would clearly be advantageous to use polar (polyspherical) coordinates and an Eckart frame. Instead, polar coordinates are generally used with a frame attached to a small number of the vectors. Unfortunately, the Eckart polyspherical KEO is complicated. It has been derived only for three-atom molecules. Using finite difference methods it is possible, without deriving a KEO, to work with polyspherical vibrational coordinates and an Eckart frame. We demonstrate that this allows us to deal with large amplitude motion and at the same time exploit the fact that an Eckart frame facilitates the choice of good basis functions.

Wang, Xiaogang; Carrington, Tucker; , Jr.

2012-06-01

96

Ultrafast relaxation inside proteins: Calculation and measurement of electron-vibration coupling in enzymes  

NASA Astrophysics Data System (ADS)

Electron-vibration coupling in alcohol dehydrogenase and zinc substituted myoglobin was calculated using a quantum mechanics/molecular mechanics method. Good agreement with experimental measurements demonstrates the viability of the method.

Cho, B. M.; Walker, R. C.; Mercer, I. P.; Gould, I. R.; Klug, D. R.

97

Limits on high-order harmonic generation from single-atom calculations  

SciTech Connect

In the quantum mechanical calculations of electron and photon emission from atoms in strong laser fields we have employed a single-active-electron (SAE) model. We determine the effect of the time varying electric field of the laser on each of the valence electrons separately. The active electron in each calculation moves in the time-independent mean field of the remaining, unexcited electrons and the nucleus. This approach works well for the rare gas atoms, at least partially because the neglected double or higher excitations involve states well above the ionization threshold. The photoelectron and photon emission spectra calculated using this technique agree quantitatively with observed emission rates. In this paper we will present a simple semiclassical model for high intensity ionization which reproduces the observed harmonic emission spectra obtained in this regime and which provides considerable insight into the dynamics of this process. The basic models has been used in the past to predict electron energy distributions in the tunneling regime and we will use it here for harmonics.

Kulander, K.C.; Schafer, K.J.

1993-08-18

98

Calculation of the vibrational frequencies and structure of zirconium tetrahydroborate  

Microsoft Academic Search

The normal mode frequencies and corresponding vibrational assignments of zirconium tetrahydroborate (Zr(BH4)4) in T symmetry are examined theoretically using the Gaussian98 set of quantum chemistry codes. All normal modes were successfully assigned to one of the six types of motion (B?H stretch, Zr?B stretch, B?Zr?B bend, H?B?H bend, BH4 wag, and BH4 twist) predicted by a group theoretical analysis. By

James O Jensen

2003-01-01

99

Conformational studies of 3-aminomethylene-2,4-pentanedione using vibrational and NMR spectra, and ab initio calculations  

NASA Astrophysics Data System (ADS)

The IR, Raman and NMR spectra of 3-aminomethylene-2,4-pentanedione (AMP) H2NCHC(COCH3)2 were measured. According to the NMR spectra in chloroform and more polar DMSO at room temperature, the sample exists as single entity. On the other hand vibrational spectra revealed that in less polar solutions AMP exists as two conformers with EZ or ZZ orientation of acetyl groups whereas in more polar solvent only one EZ conformer is observed. Such interpretation was confirmed also by the temperature-dependent measurements of IR spectra in chloroform. The observed IR and Raman bands were compared with harmonic vibrational frequencies, calculated using ab initio MP2 and B3LYP density functional methods in 6-31G?? basis set, and assigned on the basis of potential energy distribution. In addition, the geometries and relative energies of possible conformers of AMP were also evaluated at the same levels of theory and compared with the data from X-ray analysis which revealed that AMP exists in solid state as EZ conformer. The influence of environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using PCM, IPCM and ONSAGER models.

Gróf, M.; Gatial, A.; Milata, V.; Prónayová, N.; Sümmchen, L.; Salzer, R.

2007-10-01

100

Quantum chemical calculation of intramolecular vibrational redistribution and vibrational energy transfer of water clusters  

NASA Astrophysics Data System (ADS)

In present letter the adiabatic approximation is applied to the intramolecular vibrational redistribution (IVR) of water clusters. The isotope, blocking and cluster-size effects are investigated. This letter also examines the assumption associated with the transition state theory applied to unimolecular reactions; that is, IVR is assumed to be completed before the reaction takes place. For this purpose, we choose to study (H2O)2H+ ? H2O + H3O+, and (H2O)2 ? 2H2O processes. In molecular clusters, the vibrational excitation energy transfer between different normal modes has been observed. This will also be investigated for the deuterated species of (HOD)2H+.

Niu, Y. L.; Pang, R.; Zhu, C. Y.; Hayashi, M.; Fujimura, Y.; Lin, S. H.; Shen, Y. R.

2013-10-01

101

Calculation of optical excitations in cubic semiconductors. III. Third-harmonic generation  

NASA Astrophysics Data System (ADS)

Following the preceding two papers on the linear optical and second-harmonic-generation calculations on the 18 cubic semiconductors of group-IV, III-V, and II-VI compounds using the first-principles band-structure method, the two nonzero elements ?(3)1111(?) and ?(3)1212(?) of the third-order nonlinear susceptibility in these semiconductors are studied. Contributions to the third-harmonic generation from virtual-electron, virtual-hole, and three-state processes are investigated and the final results are compared with available experimental data. It is shown that the zero-frequency limits ?(3)1111(0) and ?(3)1212(0) in these crystals can vary over several orders of magnitude, yet the ratios ?(3)1212(0)/?(3)1111(0) show remarkable consistency and are in very good agreement with the available data. The frequency-dependent dispersion curves for the 18 semiconductors up to 10 eV are also calculated. For most crystals, structures are limited to the low-frequency range below 4.0 eV. For several crystals, ||?(3)(?)|| show additional resonance structures in the higher-frequency range that have never been revealed before. Correlations of ?(3)(0) with direct band gap and ?(2)(0) are investigated. There is a remarkable correlation between the direct gap and the triple of frequency of the leading peak in the dispersion curves. Our results are also compared with the other existing calculation by Moss, Ghahramani, Sipe, and van Driel on some of these crystals. We again emphasize the importance of having accurate conduction-band (CB) wave functions and in taking a sufficient number of CB states into the calculation in order to obtain converged results. This is far more important than other effects that are not taken into account in the present local-density calculation for the electronic states.

Ching, W. Y.; Huang, Ming-Zhu

1993-04-01

102

First-principles calculation of vibrational entropy for FeAl compounds  

Microsoft Academic Search

In this paper, we calculated the difference in vibrational entropy between chemically disordered and ordered Fe-Al compounds. The procedure of calculation is as follows: (1) Calculating the total-energy curves by using the ab initio band calculation method tight-binding linear muffin-tin orbital; (2) inverting the interatomic potentials involved in these Fe-Al compounds based on the lattice inversion method; (3) calculating the

Liu Shaojun; Duan Suqing; Ma Benkun

1998-01-01

103

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

PubMed

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

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

2012-11-14

104

Molecular structure and vibrational spectra of three substituted 4-thioflavones by density functional theory and ab initio Hartree-Fock calculations  

NASA Astrophysics Data System (ADS)

The vibrational frequencies of three substituted 4-thioflavones in the ground state have been calculated using the Hartree-Fock and density functional method (B3LYP) with 6-31G* and 6-31+G** basis sets. The structural analysis shows that there exists H-bonding in the selected compounds and the hydrogen bond lengths increase with the augment of the conjugate parameters of the substituent group on the benzene ring. A complete vibrational assignment aided by the theoretical harmonic wavenumber analysis was proposed. The theoretical spectrograms for FT-IR spectra of the title compounds have been constructed. In addition, it is noted that the selected compounds show significant activity against Shigella flexniri. Several electronic properties and thermodynamic parameters were also calculated.

Li, Xiao-Hong; Liu, Xiang-Ru; Zhang, Xian-Zhou

2011-01-01

105

Reduction of electromagnetic force harmonics in asynchronous traction motor by adapting the rotor slot number  

Microsoft Academic Search

The harmonics in electromagnetic force are a source of mechanical vibration and audible noise in an asynchronous traction motor. This paper describes an approach to reduce the force harmonics by changing the rotor slot number. Both the radial and tangential forces acting on the stator teeth are calculated by Maxwell stress tensor and their time harmonics are examined by the

Byung-Taek Kim; Byun-Il Kwon; Seung-Chan Park

1999-01-01

106

Tuning natural modes of vibration by prestress in the design of a harmonic gong.  

PubMed

Prestresses are purposefully added to an object to improve its performance, such as tuning a guitar string by adding tension. This paper reports how the normal modes of a sheet metal component can be tuned through the prestresses generated by cold-forging small dimples. Finite element analysis showed that the frequencies of specific mode shapes were differentially affected by the location of residual stress fields due to dimple formation in relation to modal stress fields. The frequencies of overtones were most sensitive to the depth of the dimples located near the maxima of modal stresses. Using this approach a series of musical gongs were designed with up to the first five overtones tuned to within 5% of the harmonic series. The balance of harmonic and inharmonic overtones in these gongs that are well resolved by the human cochlea may constitute a set of recognizable musical timbres with sufficient harmonicity to produce an unambiguous pitch for most listeners. Since many other mechanical properties of sheet metal components are affected by residual stresses this manufacturing technique may have broader application in design engineering. PMID:22280715

McLachlan, Neil; Adams, Ryan; Burvill, Colin

2012-01-01

107

Vibrationally averaged post Born-Oppenheimer isotopic dipole moment calculations approaching spectroscopic accuracy  

NASA Astrophysics Data System (ADS)

We report an upgrade of the Dalton code to include post Born-Oppenheimer nuclear mass corrections in the calculations of (ro-)vibrational averages of molecular properties. These corrections are necessary to achieve an accuracy of 10-4 debye in the calculations of isotopic dipole moments. Calculations on the self-consistent field level present this accuracy, while numerical instabilities compromise correlated calculations. Applications to HD, ethane, and ethylene isotopologues are implemented, all of them approaching the experimental values.

Arapiraca, A. F. C.; Jonsson, Dan; Mohallem, J. R.

2011-12-01

108

Molecular geometry and vibrational studies of 3,5-diamino-1,2,4-triazole using quantum chemical calculations and FT-IR and FT-Raman spectroscopies.  

PubMed

The 3,5-diamino-1,2,4-triazole (guanazole) was investigated by vibrational spectroscopy and quantum methods. The solid phase FT-IR and FT-Raman spectra were recorded in the region 4000-400 cm(-1) and 3600-50 cm(-1) respectively, and the band assignments were supported by deuteration effects. The results of energy calculations have shown that the most stable form is 1H-3,5-diamino-1,2,4-triazole under C1 symmetry. For this form, the molecular structure, harmonic vibrational wave numbers, infrared intensities and Raman activities were calculated by the ab initio/HF and DFT/B3LYP methods using 6-31G* basis set. The calculated geometrical parameters of the guanazole molecule using B3LYP methodology are in good agreement with the previously reported X-ray data, and the scaled vibrational wave number values are in good agreement with the experimental data. The normal vibrations were characterized in terms of potential energy distribution (PEDs) using VEDA 4 program. PMID:21112810

Guennoun, L; El jastimi, J; Guédira, F; Marakchi, K; Kabbaj, O K; El Hajji, A; Zaydoun, S

2010-10-26

109

Numerical Calculation Method for Prediction of Ground-borne Vibration near Subway Tunnel  

NASA Astrophysics Data System (ADS)

This paper describes the development of prediction method for ground-borne vibration from railway tunnels. Field measurement was carried out both in a subway shield tunnel, in the ground and on the ground surface. The generated vibration in the tunnel was calculated by means of the train/track/tunnel interaction model and was compared with the measurement results. On the other hand, wave propagation in the ground was calculated utilizing the empirical model, which was proposed based on the relationship between frequency and material damping coefficient ? in order to predict the attenuation in the ground in consideration of frequency characteristics. Numerical calculation using 2-dimensinal FE analysis was also carried out in this research. The comparison between calculated and measured results shows that the prediction method including the model for train/track/tunnel interaction and that for wave propagation is applicable to the prediction of train-induced vibration propagated from railway tunnel.

Tsuno, Kiwamu; Furuta, Masaru; Abe, Kazuhisa

110

Structure and vibrational spectra of gauche- and trans-conformers of ethanol: Nonempirical anharmonic calculations and FTIR spectra in argon matrices  

NASA Astrophysics Data System (ADS)

Low-temperature infrared absorption spectra are obtained for ethanol isolated in an argon matrix at temperatures of 20-45 K range for ratios of the numbers of the molecules being studied to the numbers of matrix atoms of 1:1000 and 1:2000. A preliminary interpretation of the spectra is obtained on the basis of the temperature variations in the spectra and published data. The structure of the ethanol conformers, rotational constants, and internal rotation barriers of the methyl and hydroxyl groups are calculated in the B3LYP/cc-pVQZ approximation. The harmonic and anharmonic IR spectra of the gauche- and trans-conformers are calculated in the same approximation. The force fields of the two conformers and the distributions of the potential energy of the normal vibrations are calculated and compared for a general set of dependent coordinates. Anharmonicity effects are taken into account by introducing spectroscopic masses for the hydrogen atoms when calculating the normal vibrations in the harmonic approximation.

Pitsevich, G. A.; Doroshenko, I. Yu.; Pogorelov, V. Ye.; Sablinskas, V.; Balevicius, V.

2013-04-01

111

Improved calculations of the lowest vibrational transitions in HeH{sup +}  

SciTech Connect

More accurate variational calculations of the lowest three pure vibrational states (v=0,1,2) of the {sup 4}HeH{sup +} molecular ion have been carried out without assuming the Born-Oppenheimer approximation. In the calculations we included the complete set of {alpha}{sup 2} relativistic corrections, i.e., mass-velocity, Darwin, spin-spin, and orbit-orbit. This allowed us to improve the agreement between the theory and the experiment for the vibrational frequencies of the 1{yields}0 and 2{yields}1 transitions as compared to our previous calculations [Stanke et al., Phys. Rev. Lett. 96, 233002 (2006)].

Bubin, Sergiy [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States); Stanke, Monika [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States); Institute of Physics, Nicholas Copernicus University, ulica Grudziadzka 5, PL 87-100 Torun (Poland); Kedziera, Dariusz [Department of Chemistry, Nicholas Copernicus University, ulica Gagarina 7, PL 87-100 Torun (Poland); Adamowicz, Ludwik [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States); Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2007-08-15

112

Consistent force field for calculation of vibrational spectra and conformations of some amides and lactam rings  

Microsoft Academic Search

The vibrations and equilibrium conformations of the linear amides N-methylformamide, acetamide, and N-methylacetamide, and the ring amides 2-pyrrolidone, 2-piperidone, and ?-caprolactam are calculated simultaneously from intramolecular energy functions. The parameters of the energy functions related to the amide group and its vicinity are optimized by least squares to give a best fit to the vibrational spectra and conformations of the

A. Warshel; M. Levitt; S. Lifson

1970-01-01

113

Exact and approximate methods for calculating log-periodic vibrator antennas  

Microsoft Academic Search

Two methods for calculating the characteristics of log-periodic vibrator antennas are discussed and compared: (1) a rigorous integral equation method with a system of piecewise-sinusoidal functions as the basis and (2) the induced-emf method. It is found that, for log-periodic antennas with a frequency band greater than one octave, the induced-emf method is applicable only when vibrators of the active

V. A. Iatskevich; V. M. Lapitskii

1979-01-01

114

Vibrational spectra, ab initio/DFT electronic structure calculations, and normal coordinate analysis of 2-bromo-5-fluorobenzaldehyde.  

PubMed

FT-IR (4000-400 cm(-1)) and FT-Raman (3500-50 cm(-1)) spectral measurements of solid samples of 2-bromo-5-fluorobenzaldehyde (BFB) have been done. Ab initio (RHF/6-311G*) and DFT (B3LY/6-311G* and B3PW91/6-311G*) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, depolarization ratios, infrared intensities, Raman activities and atomic displacements. Furthermore force field calculations have been performed by normal coordinate analysis. Force field calculations showed that several normal modes are mixed in terms of the internal coordinates. A complete assignment of the observed spectra, based on spectral correlations, electronic structure and normal coordinate analysis, has been proposed. Optimization leads to C(S) symmetry with O-trans and O-cis isomers, with respect to aldehydic oxygen and bromine, with O-trans-isomer as the low energy stable form. The energy difference between the two isomers is 2.95084 kcal/mol. The results of the calculations have been used to simulate IR and Raman spectra for BFB that showed excellent agreement with the observed spectra. The SQM method, which implies multiple scaling of the ab initio and DFT force fields has been shown superior to the uniform scaling approach. PMID:19864179

Hiremath, C S; Sundius, Tom

2009-10-06

115

Molecular structure and vibrational IR spectrum of ketene. Comparison of conventional ab initio post-Hartree—Fock and density functional theory calculations  

Microsoft Academic Search

The results of comparative quantum-mechanical studies based on conventional ab initio post-Hartree-Fock calculations, with electron correlations incorporated by second-order Mřller-Plesset perturbation theory (MP2(full)) and density functional theory with the Becke3-LYP functionals (DFT(B3-LYP)) using three basis sets 6-31G(d,p), 6-31lG(d,p) and 6-31lG(3df,2p), are reported for the molecular parameters (equilibrium geometry, rotational constants, dipole moment) and vibrational IR spectrum (harmonic wavenumbers, absolute intensities)

Józef S. Kwiatkowski; Jerzy Leszczy?ski

1995-01-01

116

Decentralized harmonic active vibration control of a flexible plate using piezoelectric actuator-sensor pairs.  

PubMed

We have investigated decentralized active control of periodic panel vibration using multiple pairs combining PZT actuators and PVDF sensors distributed on the panel. By contrast with centralized MIMO controllers used to actively control the vibrations or the sound radiation of extended structures, decentralized control using independent local control loops only requires identification of the diagonal terms in the plant matrix. However, it is difficult to a priori predict the global stability of such decentralized control. In this study, the general situation of noncollocated actuator-sensor pairs was considered. Frequency domain gradient and Newton-Raphson adaptation of decentralized control were analyzed, both in terms of performance and stability conditions. The stability conditions are especially derived in terms of the adaptation coefficient and a control effort weighting coefficient. Simulations and experimental results are presented in the case of a simply supported panel with four PZT-PVDF pairs distributed on it. Decentralized vibration control is shown to be highly dependent on the frequency, but can be as effective as a fully centralized control even when the plant matrix is not diagonal-dominant or is not strictly positive real (not dissipative). PMID:16454282

Baudry, Matthieu; Micheau, Philippe; Berry, Alain

2006-01-01

117

Calculation of harmonic radiation and nuclear coupling arising from atoms in strong laser fields  

SciTech Connect

A numerical, time-dependent quantum mechanical model is used to describe the interaction of an isolated ion with an intense applied laser field, including both electron and nuclear degrees of freedom. Calculated results are presented. We find that the model ion radiates in low odd harmonics of the laser frequency, in qualitative agreement with experimental observations. In addition, it radiates strongly in the x-ray region, at frequencies comparable with the electron Rydberg frequency. Such radiation should be possible to observe in future experiments. If it exists, it could provide a basis for a reasonably coherent x-ray source. We find that the probability of induced nuclear excitation is small for higher electric multipoles, although observable probabilities are obtained under appropriate circumstances for L = 1. 2 refs., 12 figs.

Rinker, G.A.; Solem, J.C.; Biedenharn, L.C.

1988-01-01

118

Analytical transformed harmonic oscillator basis for continuum discretized coupled channels calculations  

SciTech Connect

A new method for continuum discretization in continuum-discretized coupled-channels calculations is proposed. The method is based on an analytic local-scale transformation of the harmonic-oscillator wave functions proposed for other purposes in a recent work [Karatagladis et al., Phys. Rev. C 71, 064601 (2005)]. The new approach is compared with the standard method of continuum discretization in terms of energy bins for the reactions d+{sup 58}Ni at 80 MeV, {sup 6}Li+{sup 40}Ca at 156 MeV, and {sup 6}He+{sup 208}Pb at 22 MeV and 240 MeV/nucleon. In all cases very good agreement between both approaches is found.

Moro, A. M.; Arias, J. M. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Fisica, Universidad de Sevilla, Apartado 1065, E-41080 Sevilla (Spain); Gomez-Camacho, J. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Fisica, Universidad de Sevilla, Apartado 1065, E-41080 Sevilla (Spain); Centro Nacional de Aceleradores, Avda Thomas A. Edison, E-41092 Sevilla (Spain); Perez-Bernal, F. [Departamento de Fisica Aplicada, Universidad de Huelva, E-21071 Huelva (Spain)

2009-11-15

119

Calculation of structures and vibrational spectra of acetonitrile clusters  

Microsoft Academic Search

The minimum energy structures of acetonitrile clusters from n=2 to n=13 have been calculated using a total cluster potential which is composed from a semi-empirical intermolecular potential in combination with the intramolecular force field. Based on these results the frequency shifts of the CC stretch and the CH3 wag modes are calculated and compared with recent measurements of size selected

J. G. Siebers; U. Buck; T. A. Beu

1998-01-01

120

Microwave, infrared, and Raman spectra, structural parameters, vibrational assignments and theoretical calculations of 1,3-disilacyclopentane  

NASA Astrophysics Data System (ADS)

The FT-microwave spectrum of 1,3-disilacyclopentane (c-C3H6Si2H4) has been recorded and 99 transitions for five isotopologues have been assigned for the twist form. The ground state rotational constants were determined from these assignments with following values for A = 4417.6710(7), B = 2887.0548(6), C = 1938.2171(6). From the experimentally reported microwave rotational constants and ab initio MP2(full)/6-311+G(d,p) predicted structural values, adjusted r0 parameters are reported for the most stable twist form distances (Ĺ) rC?Si = 1.886(2), rSiC?,C?? = 1.888(2), rC?C?? = 1.552(2), and angles (°) ?SiC?Si = 103.9(3), ?C?SiC? = 102.2(3), ?SiC?C?? = 106.4(3), and ?C?SiC?Si = 11.5(3), ?SiC?C??Si = 45.6(3). The conformational stabilities have been predicted from theoretical calculations with basis sets up to aug-cc-pVTZ from both MP2(full) and density functional theory calculations by the B3LYP method. Vibrational assignments have been made for the observed bands for the twist conformer and the interpretation is utilized by ab initio calculations to predict harmonic force constants, vibrational wavenumbers, infrared intensities, Raman activities and depolarization ratios. The results are discussed and compared to the corresponding properties of some related molecules.

Guirgis, Gamil A.; Klaassen, Joshua J.; Pate, Brooks H.; Seifert, Nathan A.; Darkhalil, Ikhlas D.; Deodhar, Bhushan S.; Wyatt, Justin K.; Dukes, Horace W.; Kruger, Michael; Durig, James R.

2013-10-01

121

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  

NASA Astrophysics Data System (ADS)

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.

Ramalingam, S.; Periandy, S.

2011-03-01

122

Vibrational zero-point energies and thermodynamic functions beyond the harmonic approximation.  

PubMed

This paper compares harmonic and anharmonic zero-point energies and thermodynamic functions for a number of molecules of small and medium size. Anharmonic corrections cannot be neglected for quantitative studies, but can be obtained quite effectively by a perturbative treatment including cubic force constants to the second order and semidiagonal quartic constants to the first order. Simple finite difference equations provide all the necessary terms by at most 6N-11 Hessian evaluations, where N is the number of atoms in the system. Accurate values are obtained by this method using the Becke three parameter Lee-Yang-Parr functional, medium size basis sets, and, when needed, proper treatment of internal rotations. The whole model has been completely automated in the Gaussian package. PMID:15268458

Barone, Vincenzo

2004-02-15

123

Calculation of vibrational frequencies in large molecules . Part II. Application to ethane and ethane-d6  

Microsoft Academic Search

The theory developed in the preceding paper for calculating the vibrational frequencies of molecules in terms of mixtures of vibrations within groups, and skeletal vibrations due to group rotations and translations, is applied to C2H6 and C2D6. It is shown that the matrix elements in the secular equation which reveal the couplings between the intragroup vibrations on the two CH3

H. L. McMurry

1959-01-01

124

A simplified spherical harmonic method for coupled electron-photon transport calculations  

SciTech Connect

In this thesis the author has developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. He has performed a first time Fourier analysis of the source iteration scheme and the P{sub 1} diffusion synthetic acceleration (DSA) scheme applied to the 2-D SP{sub N} equations. The theoretical analyses indicate that the source iteration and P{sub 1} DSA schemes are as effective for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. In addition, he has applied an angular multigrid acceleration scheme, and computationally demonstrated that it performs as well as for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. It has previously been shown for 1-D S{sub N} calculations that this scheme is much more effective than the DSA scheme when scattering is highly forward-peaked. The author has investigated the applicability of the SP{sub N} approximation to two different physical classes of problems: satellite electronics shielding from geomagnetically trapped electrons, and electron beam problems.

Josef, J.A.

1997-12-01

125

Simplified spherical harmonic method for coupled electron-photon transport calculations  

NASA Astrophysics Data System (ADS)

In this paper we apply the simplified spherical harmonic (SPN) approximation to coupled electron-photon transport problems in two-dimensional cylindrical geometry in the energy range from roughly 10 keV to 10 MeV. The SPN equations represent an asymptotic approximation that does not necessarily converge to the exact transport solution as N-->?, but can sometimes produce solutions that are much more accurate than diffusion theory at a fraction of the cost of a full transport treatment. To our knowledge, the SPN approximation has previously been applied only to neutron transport problems. We investigate the applicability of the SPN method to satellite electronics shielding calculations. In addition to applying the approximation, we generalize certain iterative convergence acceleration techniques originally developed for the one-dimensional SN (discrete ordinates) equations, and apply them to the two-dimensional SPN equations. We present numerical comparisons with Monte Carlo calculations for the purpose of examining both the accuracy of the SPN approximation and the computational efficiency of our solution techniques.

Josef, J. A.; Morel, J. E.

1998-05-01

126

Using steady state vibrational temperatures to model effects of N2* on calculations of electron densities  

NASA Astrophysics Data System (ADS)

Measurements of NmF2 and hmF2 at Millstone Hill are compared with results from the Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN) time-dependent mathematical model of the Earth's ionosphere and plasmasphere during the periods March 16-23 and April 6-12, 1990. The effects of vibrationally excited N2 are studied by using two approaches: (1) obtaining a full solution of the vibrational quanta continuity equation and (2) calculating an analytical solution of the steady state vibrational quanta continuity equation using a simple FORTRAN subroutine. It is shown that during both undisturbed periods and magnetic storms the full solution and the analytical approach give very similar results for NmF2 and hmF2 derived from the IZMIRAN model, so the analytical approach can be recommended for use in ionospheric models for calculation of electron densities during both quiet and disturbed conditions.

Pavlov, A. V.; Buonsanto, M. J.

1996-12-01

127

Numerical calculation for determining sonar self noise sources due to structural vibration  

Microsoft Academic Search

It is important to determine dominant sonar self noise sources on a ship due to structural vibration. Much computation time is required for conventional simulation methods like BEM because it needs matrix inversion to determine the sound pressure on the radiating surface. In this paper, the simplified simulation method which reduces the calculation by using a vibro-acoustic transfer function is

Takaaki Musha; Tatsuo Kikuchi

1999-01-01

128

Free vibration of rotating non-uniform discs: Spline interpolation technique calculations  

Microsoft Academic Search

Stress distributions and flexural vibration of rotating annular discs with radially varying thickness are calculated by means of a spline interpolation technique. For this purpose, the disc is divided into many ring-shaped elements and the radial displacement is expressed as a cubic spline function, which satisfies the equation of equilibrium of force at all the knots and also satisfies boundary

T. Irie; G. Yamada; R. Kanda

1979-01-01

129

Vibrations  

NASA Astrophysics Data System (ADS)

Low frequent vibrations may cause from disturbing up to damaging effects. There is no precise distinction between structure-borne sound and vibrations. However - depending on the frequency range - measurements and predictions require different techniques. In a wide frequency range, the generation, transmission and propagation of vibrations can be investigated similar to structure-borne sound (see Chap. 9).

Guggenberger, Johannes; Müller, Gerhard

130

Convergence properties of ab initio calculations of light nuclei in a harmonic oscillator basis  

NASA Astrophysics Data System (ADS)

We study recently proposed ultraviolet and infrared momentum regulators of the model spaces formed by construction of a variational trial wave function which uses a complete set of many-body basis states based upon three-dimensional harmonic oscillator (HO) functions. These model spaces are defined by a truncation of the expansion characterized by a counting number (N) and by the intrinsic scale (??) of the HO basis—in short by the ordered pair (N,??). In this study we choose for N the truncation parameter Nmax related to the maximum number of oscillator quanta, above the minimum configuration, kept in the model space. The uv momentum cutoff of the continuum is readily mapped onto a defined uv cutoff in this finite model space, but there are two proposed definitions of the ir momentum cutoff inherent in a finite-dimensional HO basis. One definition is based upon the lowest momentum difference given by ?? itself and the other upon the infrared momentum which corresponds to the maximal radial extent used to encompass the many-body system in coordinate space. Extending both the uv cutoff to infinity and the ir cutoff to zero is prescribed for a converged calculation. We calculate the ground-state energy of light nuclei with “bare” and “soft” nucleon-nucleon (NN) interactions. By doing so, we investigate the behaviors of the uv and ir regulators of model spaces used to describe 2H, 3H, 4He, and 6He with NN potentials Idaho N3LO and JISP16. We establish practical procedures which utilize these regulators to obtain the extrapolated result from sequences of calculations with model spaces characterized by (N,??).

Coon, S. A.; Avetian, M. I.; Kruse, M. K. G.; van Kolck, U.; Maris, P.; Vary, J. P.

2012-11-01

131

Calculations of stretching vibrational energy levels of the CH3I molecule by a nonlinear model  

Microsoft Academic Search

A nonlinear model, i.e. the quantized discrete self-trapping equation, is applied to calculate the highly excited CH stretching vibrational energy levels of the CH3I molecule in the liquid phase at the electronic ground state up to n=8. The obtained results agree well with the experimental data and with those obtained from local mode model calculations. We note that the dominant

Jun Zhu; Qing-quan Gou

2001-01-01

132

First-principles calculations of the vibrational spectra of one-dimensional C60 polymers  

NASA Astrophysics Data System (ADS)

The vibrational properties of several C60 dimers belonging to the Stone-Wales rearrangement sequence [described by E. Osawa and K. Honda, Full. Sci. Technol. 4, 939 (1996)], along with a trimer and a tetramer isomer are investigated by tight-binding and density functional calculations. The IR absorption bands found by Onoe, Nakayama, Aono and Hara [Appl. Phys. Lett. 82, 595 (2003)] in the spectra of electron-beam irradiated C60 films are explained and attributed mainly to surface vibrations located in the waist region of the considered polymers. The features of the Raman spectra are also discussed and related to experimental spectra of photopolymerized C60 .

Beu, Titus A.; Onoe, Jun

2006-11-01

133

Multidimensional local mode calculations for the vibrational spectra of OH(-)(H2O)2 and OH(-)(H2O)2ˇAr.  

PubMed

Multidimensional local mode calculations are performed for OH stretching vibrations of the gas phase OH(-)(H2O)2 and OH(-)(H2O)2ˇAr clusters in the 1000-4000 cm(-1) energy range. The potential energies and the associated dipole moment values are calculated with MP2/6-311++G(3df,3pd). To fully take into account the anharmonic effects for the stretching vibrations of the ionic hydrogen bonded OHs (IHB OHs), those donating H to the O atom in OH(-), the vibrational Hamiltonian represented by the discrete variable representation (DVR) technique is diagonalized without using any truncation/contraction scheme for the basis. The necessary potential energies and dipole moment values at the DVR grid points are supplied by the polynomial inter- and extrapolations based on the values calculated at fine spatial grid points. We found that the peaks at 2700 cm(-1) should be assigned to the first overtone (?: 0 ? 2) of the IHB OH stretching vibrations rather than the previous assignment of the fundamental of the IHB OH based on harmonic frequencies. The relevant fundamental peaks should be observed around 1600-2000 cm(-1) where no experimental observation has been performed. This prediction of the fundamental peak positions leads to a simple correlation between the magnitude of the red-shift of the IHB OH stretching vibrational peak position and the cluster size of OH(-)(H2O)n for n = 1-3. Furthermore, to determine important contributions toward the assignment of the experimental spectrum, detailed analyses are performed from the following 3 viewpoints: (1) mode coupling between the inter water IHB OH stretching vibrations, (2) coupling between the IHB OH and the low-frequency OO stretching vibrations and (3) argon attachment to OH(-)(H2O)2. We found that the overall shape of the vibrational spectrum can be essentially described by considering only factor (1). However, fairly large peak shifts are caused by factors (2) and (3). PMID:23912845

Morita, Masato; Takahashi, Kaito

2013-08-21

134

Nuclear Quantum Vibrational Effects in Shock Hugoniot Temperatures  

Microsoft Academic Search

We present a straightforward method for the inclusion of quantum nuclear vibrational effects in molecular dynamics calculations of shock Hugoniot temperatures. Using a Griineisen equation of state and a quasi-harmonic approximation to the vibrational energies, we derive a simple, post-processing method for calculation of the quantum corrected Hugoniot temperatures. We have used our technique on ab initio simulations of shock

Nir Goldman; Evan J. Reed; Laurence E. Fried

2009-01-01

135

NUCLEAR QUANTUM VIBRATIONAL EFFECTS IN SHOCK HUGONIOT TEMPERATURES  

Microsoft Academic Search

We present a straightforward method for the inclusion of quantum nuclear vibrational effects in molecular dynamics calculations of shock Hugoniot temperatures. Using a Griineisen equation of state and a quasi-harmonic approximation to the vibrational energies, we derive a simple, post-processing method for calculation of the quantum corrected Hugoniot temperatures. We have used our technique on ab initio simulations of shock

Nir Goldman; Evan J. Reed; Laurence E. Fried

2009-01-01

136

2D calculation of anharmonic OH vibrations in a layered hydroxide crystal  

NASA Astrophysics Data System (ADS)

Anharmonic vibrational frequencies for the Raman-active (A1g) and the IR-active (A2u) modes have been calculated for the LiOH crystal within a plane-wave density functional theory (DFT) framework. We find that a two-dimensional quantum-mechanical vibrational approach, allowing for anharmonic coupling between symmetric and antisymmetric OH stretching modes, produces OH frequencies-both absolute frequencies and gas-to-solid frequency shifts-in good agreement with experiment. Remaining errors in the absolute frequencies are largely a consequence of the DFT model chosen. A one-dimensional normal-mode following vibrational treatment, on the other hand, fails to reproduce both absolute anharmonic frequencies and gas-to-solid frequency shifts.

Gajewski, Grzegorz; Mitev, Pavlin D.; Hermansson, Kersti

2008-08-01

137

Vibrational spectroscopic and DFT calculation studies of cobalt(II) complexes with 3-hydroxypicolinic acid.  

PubMed

Two cobalt(II) complexes with 3-hydroxypicolinic acid (3-hydroxypyridine-2-carboxylic acid, 3-OHpicH), trans-[Co(3-OHpic)2(py)2] (2) and cis-[Co(3-OHpic)2(4-pic)2] (3) (py=pyridine; 4-pic=4-picoline or 4-methylpyridine), previously synthesized and characterized by X-ray diffraction, are here studied by Raman and mid-infrared spectroscopy with the help from the corresponding DFT vibrational calculations using B3LYP/6-311G(d,p) computational model. Intramolecular O-H?O hydrogen bond appears in both complexes 2 and 3, while weak C-H?O hydrogen bonds assemble molecules of 2 or 3 into 3D architecture. A complete presentation of all Raman, infrared and theoretical results is given for complex 3. The measured spectra are shown, relative intensities and bandwidths are discussed and the assignment of vibrational bands is given on the basis of the DFT calculations. The calculated spectra agree very well with the presented experimental findings, thanks to the suitable grouping of modes. The same vibrational calculations also reveal insignificant influence of H?CH3 substitution for the spectroscopic characterization of the complex. A careful study of differences between calculated and observed wavenumbers suggests that modified single-factor scaling is actually better than the classic multi-factor scaling approach. PMID:23103469

Furi?, Krešimir; Kodrin, Ivan; Kukovec, Boris-Marko; Mihali?, Zlatko; Popovi?, Zora

2012-10-04

138

A numerical code for the calculation of relativistic electron cyclotron damping with an arbitrary distribution function at an arbitrary harmonic  

NASA Astrophysics Data System (ADS)

The relativistic expressions for the anti-Hermitian parts of the relativistic dielectric tensor elements can be expressed as a single integral over the parallel momentum variable, allowing an arbitrary electron distribution function. A computer program has been written for the calculation of this single integral. The numerical results are tested for a relativistic Maxwellian distribution function and agree with analytical expressions for this case. The numerical code is therefore an essential element in a more general validation, evaluation and demonstration of powerful analytical results presented. The computer program is then applied to the calculation of relativistic electron cyclotron harmonic damping at any arbitrary harmonic, for any distorted electron distribution function, distorted for example by an electric field or by RF power sources, as for instance by both electron cyclotron and lower-hybrid waves, as calculated from a relativistic Fokker-Planck code. For generality, we also include the case of relativistic Landau damping, also used to check the code.

Shkarofsky, I.; Shoucri, M.

2011-07-01

139

Vibrational spectral analysis, computation of thermodynamic functions for various temperatures and NBO analysis of 2,3,4,5-tetrachlorophenol using ab initio HF and DFT calculations.  

PubMed

FT-IR and FT-Raman spectra of 2,3,4,5-tetrachlorophenol (TCP) have been recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1) respectively. The total energy calculations of TCP were tried for the possible conformers. The molecular structure, geometry optimization, vibrational frequencies were obtained by the ab initio and DFT levels of theory (B3LYP and B3PW91) with the standard basis sets, 6-311++G(d, p) and 6-311+G(d, p) for C1 and C2 conformers. The harmonic frequencies were calculated and the scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The thermodynamic functions (heat capacity, entropy, vibrational partition function and Gibbs energy) from spectroscopic data by statistical methods were obtained for the range of temperature 100-1000 K. The polarizability, first hyperpolarizability, anisotropy polarizability invariant has been computed using quantum chemical calculations. The chemical parameters were calculated from the HOMO and LUMO values. PMID:23123243

Balachandran, V; Rajeswari, S; Lalitha, S

2012-10-12

140

Vibrational spectral analysis, computation of thermodynamic functions for various temperatures and NBO analysis of 2,3,4,5-tetrachlorophenol using ab initio HF and DFT calculations  

NASA Astrophysics Data System (ADS)

FT-IR and FT-Raman spectra of 2,3,4,5-tetrachlorophenol (TCP) have been recorded in the regions 4000-400 cm-1 and 3500-100 cm-1 respectively. The total energy calculations of TCP were tried for the possible conformers. The molecular structure, geometry optimization, vibrational frequencies were obtained by the ab initio and DFT levels of theory (B3LYP and B3PW91) with the standard basis sets, 6-311++G(d, p) and 6-311+G(d, p) for C1 and C2 conformers. The harmonic frequencies were calculated and the scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The thermodynamic functions (heat capacity, entropy, vibrational partition function and Gibbs energy) from spectroscopic data by statistical methods were obtained for the range of temperature 100-1000 K. The polarizability, first hyperpolarizability, anisotropy polarizability invariant has been computed using quantum chemical calculations. The chemical parameters were calculated from the HOMO and LUMO values.

Balachandran, V.; Rajeswari, S.; Lalitha, S.

2013-01-01

141

Ab initio calculation of vibrational properties of a-Si:H with inner voids  

NASA Astrophysics Data System (ADS)

We have performed an ab initio calculation of vibrational properties of hydrogenated amorphous silicon (a-Si:H) using a molecular dynamics method. A Wooten, Winer, Weaire (WWW) 216 atom model for pure amorphous silicon (a-Si) updated by Djordjevic, Thorpe and Wooten has been employed as a ``base'' for our a-Si:H models with voids that were made by removing a cluster of silicon atoms out of the bulk and terminating the resulting dangling bonds with hydrogens. Our calculation shows that the presence of voids leads to localized low energy (30-50 cm-1) states in vibrational spectrum of the system. The nature and localization properies of these states are carefully analysed by various visualization techniques. Web resources: http://www.phy.ohiou.edu/ ?nakhmans/Professional/Bubbles/bubpr.htm

Nakhmanson, S. M.; Drabold, D. A.

1998-05-01

142

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)

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.

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

2013-03-01

143

FT-IR, FT-Raman, NMR and UV-vis spectra, vibrational assignments and DFT calculations of 4-butyl benzoic acid  

NASA Astrophysics Data System (ADS)

The solid phase FTIR and FT-Raman spectra of 4-butyl benzoic acid (4-BBA) have been recorded in the regions 400-4000 and 50-4000 cm -1, respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-311++G(d,p) as basis set. The vibrational frequencies were calculated for monomer and dimer by DFT method and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. 13C and 1H NMR spectra were recorded and 13C and 1H nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV-visible spectrum of the compound was recorded in the region 200-400 nm and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. The geometric parameters, energies, harmonic vibrational frequencies, IR intensities, Raman intensities, chemical shifts and absorption wavelengths were compared with the available experimental data of the molecule.

Karabacak, M.; Cinar, Z.; Kurt, M.; Sudha, S.; Sundaraganesan, N.

2012-01-01

144

A comparison of force fields and calculation methods for vibration intervals of isotopic H+3 molecules  

Microsoft Academic Search

This paper reports (a) improved values for low-lying vibration intervals of H+3, H2D+, D2H+, and D+3 calculated using the variational method and Simons–Parr–Finlan representations of the Carney–Porter and Dykstra–Swope abinitio H+3 potential energy surfaces, (b) quartic normal coordinate force fields for isotopic H+3 molecules, (c) comparisons of variational and second-order perturbation theory, and (d) convergence properties of the Lai–Hagstrom internal

Grady D. Carney; Steven M. Adler-Golden; David C. Lesseski

1986-01-01

145

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

Microsoft Academic Search

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

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

1986-01-01

146

How to calculate the vibration of an inhomogeneous string using MATLAB programs  

NSDL National Science Digital Library

This paper presents a solution to the dynamics of a vibrating inhomogeneous string by the method of separation of variables in x and t. The solution consists in transforming the differential equation in x into an integral equation, which is subsequently solved by means of a spectral method. As an extension of a paper in the American Journal of Physics, this material describes and makes available the MATLAB programs required for the spectral calculations.

Rawitscher, George

2011-07-31

147

A simplified spherical harmonic method for coupled electron-photon transport calculations  

SciTech Connect

In this thesis we have developed a simplified spherical harmonic method (SP{sub N} method) and associated efficient solution techniques for 2-D multigroup electron-photon transport calculations. The SP{sub N} method has never before been applied to charged-particle transport. We have performed a first time Fourier analysis of the source iteration scheme and the P{sub 1} diffusion synthetic acceleration (DSA) scheme applied to the 2-D SP{sub N} equations. Our theoretical analyses indicate that the source iteration and P{sub 1} DSA schemes are as effective for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. Previous analyses have indicated that the P{sub 1} DSA scheme is unstable (with sufficiently forward-peaked scattering and sufficiently small absorption) for the 2-D S{sub N} equations, yet is very effective for the 1-D S{sub N} equations. In addition, we have applied an angular multigrid acceleration scheme, and computationally demonstrated that it performs as well for the 2-D SP{sub N} equations as for the 1-D S{sub N} equations. It has previously been shown for 1-D S{sub N} calculations that this scheme is much more effective than the DSA scheme when scattering is highly forward-peaked. We have investigated the applicability of the SP{sub N} approximation to two different physical classes of problems: satellite electronics shielding from geomagnetically trapped electrons, and electron beam problems. In the space shielding study, the SP{sub N} method produced solutions that are accurate within 10% of the benchmark Monte Carlo solutions, and often orders of magnitude faster than Monte Carlo. We have successfully modeled quasi-void problems and have obtained excellent agreement with Monte Carlo. We have observed that the SP{sub N} method appears to be too diffusive an approximation for beam problems. This result, however, is in agreement with theoretical expectations.

Josef, J.A.

1996-12-01

148

Acquisition time calculation and influence of vibrations for microsatellite laser communication in space  

NASA Astrophysics Data System (ADS)

The first step in creating an optical link between two LEO satellites is acquisition. In this process one of the satellites finds the maximal power of a received beam and locks on to it. This starts the tracking. In this paper we examine the time needed to finish the acquisition process and start tracking. The parameters included are the distribution function of satellite position, the size of the uncertainty area, the number of possible satellite positions, and the detection ability of a CCD. A model for the distribution function of position is given for two types of distribution: Gaussian and Uniform. Also considered the vibrations that come from internal systems of satellite, and from external sources. The characteristics of vibrations are considered and their influence on the scanning pattern that can deviate from the original path. A method of filtering the vibrations and compensating for them is suggested. The pointing system must be updated continuously from the star tracker with internal calculations of position, speed, velocity and vibrations characteristics. Examined also are several scanning methods: raster, spiral, Lissajo, Rose. Each method has its own possibilities and advantages, which are compared.

Scheinfeild, Michael; Kopeika, Norman S.; Arnon, Shlomi

2001-08-01

149

Design requirements and calculated performance of an XUV FEL oscillator operating on a higher harmonic  

SciTech Connect

We study, using numerical simulation methods, the design requirements for the electron beam, wiggler, and optical resonator of an extreme-ultraviolet (XUV, 100 nm {ge} {lambda} {ge} 10 nm) free-electron laser oscillator operating on a higher harmonic. Our previous theoretical studies of an XUV FEL oscillator have assumed operation at the fundamental wavelength. Higher harmonic operation is attractive because the energy of the electrons can be reduced, thus reducing the cost of the linac. A further reduction in beam energy is possible with the use of short-period wigglers: in the present work, we use the expected properties of pulsed-wire wigglers. Operation of an FEL oscillator on the third harmonic has been experimentally demonstrated at Stanford University and Los Alamos, and this mode of operation may also be both possible and desirable for an XUV device. 12 refs., 2 tabs.

Goldstein, J.C.; Warren, R.W.; Newnam, B.E.

1990-01-01

150

Converged quantum dynamics calculations of vibrational energies of CH4 and CH3D using an ab initio potential  

NASA Astrophysics Data System (ADS)

Exact variational calculations of vibrational energies of CH4 and CH3D are carried out using a two-layer Lanczos algorithm based on the ab initio potential energy surface of D. W. Schwenke and H. Partridge, Spectrochim. Acta, Part A 57, 887 (2001). The convergence of the calculated vibrational energies is discussed in detail. In addition, we report all well converged vibrational energy levels up to 6600 cm-1 for CH4, and those up to 5000 cm-1 for CH3D, respectively. These results clearly outperform previous theoretical calculations. And a comparison with experimental results available is also made.

Yu, Hua-Gen

2004-10-01

151

Converged quantum dynamics calculations of vibrational energies of CH4 and CH3D using an ab initio potential.  

PubMed

Exact variational calculations of vibrational energies of CH4 and CH3D are carried out using a two-layer Lanczos algorithm based on the ab initio potential energy surface of D. W. Schwenke and H. Partridge, Spectrochim. Acta, Part A 57, 887 (2001). The convergence of the calculated vibrational energies is discussed in detail. In addition, we report all well converged vibrational energy levels up to 6600 cm(-1) for CH4, and those up to 5000 cm(-1) for CH3D, respectively. These results clearly outperform previous theoretical calculations. And a comparison with experimental results available is also made. PMID:15446929

Yu, Hua-Gen

2004-10-01

152

Vibrational optical activity in perturbed degenerate modes: Concepts and model calculations in 1-substituted haloethanes  

NASA Astrophysics Data System (ADS)

Vibrational optical activity arising from perturbed degenerate modes (PDM) is defined in terms of the chiral perturbation of symmetric chemical groups containing degenerate pairs of modes. This approach predicts that each such degenerate pair of vibrations will give rise to a couplet signal having equal and opposite VOA intensity for the two modes. The PDM formalism is developed explicitly for the case of a chemical group of C3v symmetry in vibrational circular dichroism (VCD), which complements earlier descriptions of degeneracy in Raman optical activity (ROA). Calculations using the fixed partial charge (FPC) model for VCD and the atom dipole interaction (ADI) model of ROA were carried out for the molecules (R)-1-bromo-1-chloro-1-fluoroethane and (S)-1-chlor-1-fluoroethane-1-d1 (and d0) as simple examples of molecules with a methyl group in a chiral environment. To further analyze the nature of the chiral perturbation of the methyl group, VOA calculations for bromochlorofluoroethane were carried out for perturbations of charge or polarizability, mass, geometry and potential energy, applied individually and in combination to the symmetric parent molecule 1,1,1-trichloroethane. In most cases degenerate mode pairs gave calculated VOA couplets of nearly equal and opposite intensity. The signs and magnitudes of these couplets are discussed in relation to the perturbations applied. It is found that different types of degenerate vibrations behave differently thus reducing the scope of generalizations regarding the effect of the chiral perturbations. However, a more consistent picture emerges if the net sign of the combined VOA from each degenerate mode pair is used and a strong correlation of these signs to the sign of the methyl torsion mode is apparent. The significance of these results to actual VOA observation and interpretation is discussed.

Nafie, Laurence A.; Polavarapu, Prasad L.; Diem, Max

1980-10-01

153

FT-IR and Raman spectra, DFT and SQMFF calculations for geometrical interpretation and vibrational analysis of 3-nitro-p-toluic acid  

NASA Astrophysics Data System (ADS)

The Fourier transform infrared (FT-IR) and FT-Raman of 3-nitro-p-toluic acid (NTA) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of ab initio and density functional theory (DFT) methods. 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 optimized geometric bond lengths and bond angles obtained by computation show good agreement with experimental data of the relative compound. The computed dimer parameters also show good agreement with experimental data. The first hyperpolarizability (?0) of this noval molecular system and related properties (?, ?0, and ??) of NTA are calculated using B3LYP/6-311++G(d,p) method on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the ?\\midast and ?\\midast antibonding orbital and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The calculated HOMO and LUMO energies also show that charge transfer occurs within the molecule. Finally the calculations results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra.

Nataraj, A.; Balachandran, V.; Karthick, T.

2012-08-01

154

Synthesis, spectroscopy (vibrational, NMR and UV–vis) studies, HOMO–LUMO and NBO analysis of 8-formyl-7-hydroxy-4-methylcoumarin by ab initio calculations  

NASA Astrophysics Data System (ADS)

In this work, 8-formyl-7-hydroxy-4-methylcoumarin has been synthesized and characterized by elemental analysis, FT-IR, FT Raman, 1H NMR, 13C NMR and UV–vis spectra. The molecular geometry, harmonic vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C chemical shift values of the title compound in the ground state have been calculated by using Hartree-Fock (HF) and density functional methods (B3LYP) with 6-311++G(d,p) as basis set. The vibrational assignments of wave numbers were interpreted in terms of potential energy distribution (PED) analysis and the scaled B3LYP/6-311++G(d,p) results show the good agreement with the experimental values. The UV spectra of investigated compound were recorded in the region of 230–500 nm in chloroform solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) in gas and CHCl3 theoretically and results were compared with experimental observations. The molecular stability arising from hyperconjugative interactions and charge delocalization have been analyzed using natural bond orbital (NBO) analysis. In addition, Frontier Molecular Orbitals (FMO), Molecular Electrostatic Potential (MEP) and thermodynamic properties of the studied compound such as heat capacity (C), entropy (S) and enthalpy changes (H) at different temperatures have been calculated.

Moghanian, Hassan; Mobinikhaledi, Akbar; Monjezi, Roya

2013-11-01

155

Atomic hydrogen on the Pt(111) surface: ab-initio calculation of 3D vibrational modes  

NASA Astrophysics Data System (ADS)

We present the results of an ab-initio calculation for the H/Pt(111) system. Using the supercell method and a plane wave expansion, the H/Pt interaction potential is found. Our results agree with other recent calculations (G.Papoian, J.K.Norskov, R.Hoffman, J.Am.Chem.Soc. 122, 4129 (2000); R.A.Olsen, G.J.Kroes, E.J.Baerends, J.Chem.Phys. 111(24), 11155 (1999)). In particular, it is shown that the atop site is a stable adsorbtion site, which distinguishes H adsorption on Pt from other transition metals. A 3D vibrational band structure is built using the obtained potential and the corresponding most localized Wannier States are found by implementing Marzari and Vanderbilt's algorithm (N.Marzari, D.Vanderbilt, Phys.Rev.B, Vol.56, No.20, 12847 (1997) ). The in-plane, out-of-plane or hybridized symmetry of the vibrational states are identified with the help of these localized states . Finally, we compare the existing electron and He scattering data for this system to our new results for the vibrational states.

Badescu, Stefan; Ying, See-Chen; Salo, Petri; Ala-Nissila, Tapio; Alatalo, Matti; Trushin, Oleg

2001-03-01

156

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

NASA Astrophysics Data System (ADS)

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 ? ??, ? ? ??).

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

2012-12-01

157

Multi-input multi-output feedforward control of multi-harmonic gearbox vibrations using parallel adaptive notch filters in the principal component space  

NASA Astrophysics Data System (ADS)

Rotating mechanical systems such as gearbox are known to generate vibrations at specific frequencies. The generation of asymmetric frequency sidebands around gear meshing frequencies is typical of rotating systems, and often results in amplitude-modulated disturbances. In addition, when the angular speed of such systems exhibits small time variations, a frequency-modulation of the disturbance tones is observed. Such conditions may result in difficulties for feedforward active control systems based on short, finite impulse response control filters, as was observed by previous researchers. This is mainly due to the fact that the reference signal may not provide all the gear meshing frequencies and sidebands found in the disturbance. This work investigates adaptive notch filters in the principal component space to cancel multi-harmonic gearbox vibrations. Experimental results obtained with these adaptive notch filters show good control attenuations at targeted gearbox tones, without amplification of other closely located, unreferenced tones.

Pasco, Yann; Robin, Olivier; Bélanger, Pierre; Berry, Alain; Rajan, Srivatsa

2011-10-01

158

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

NASA Astrophysics Data System (ADS)

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.

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

2011-09-01

159

Calculated and Experimental Vibrational Properties of P700 and the Iron Sulfur Cluster in Photosystem I  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) based vibrational frequency calculations of Fe4S4(SR)4^n- clusters show that the intense iron-sulfur stretching modes lie in the frequency region between 300-400 cm-1. Among them the iron-sulfur ligand (Fe-S^t) stretching modes are more intense and ˜ 30 cm-1 lower in frequency than the iron-sulfur body (Fe-S^b) stretching modes. Calculations in tetrahydrofuran (THF) show that all these iron-sulfur stretching modes of vibration downshift by ˜ 20 cm-1 upon reduction of the molecule. On the other hand, we have not observed any intense bands from chlorophyll a in the frequency region 400 to 320 cm-1 from the calculations. In an attempt to detect modes associated with iron sulfur clusters in PS I we have obtained light induced (P700^+ - P700) FTIR difference spectra for PSI particles from S. 6803 in the far infrared region. We observe difference bands at many frequencies in the 600-300 cm-1 region. Based on our calculations and literature values we claim that the negative bands at 388 cm-1 and 353 cm-1 in the (P700^+ - P700) FTIR difference spectra be assigned to Fe-S^b and Fe-S^t stretching modes of the ground state of the iron-sulfur cluster FB.

Lamichhane, Hari; Hastings, Gary

2009-11-01

160

The ab initio assigning of the vibrational probing modes of tryptophan: linear shifting of approximate anharmonic frequencies vs. multiplicative scaling of harmonic frequencies.  

PubMed

To gain insight into the prospects for a few-dimensional ab initio quantum-mechanical description of the vibrational motions of conformationally flexible molecular systems, the NH-, NH(2)-, CO- and OH-stretching and COH-bending vibrations of the most stable tryptophan conformations have been probed using simple one- and two-dimensional anharmonic Hamiltonians and potential energy functions evaluated by means of the standard RI-MP2, CCSD(T) and DFT-D quantum chemical procedures. Although strongly dependent on the procedure used, the calculated vibrational spectral patterns have been found to be in a robust one-to-one harmony with their experimental counterparts, thus proving the adequacy of the theory used for the reliable assignment of the experimental data. Therefore, the approach appears to be a suitable tool for assigning the vibrational probing modes even of systems which are too large to be tractable by the standard normal-coordinate analysis. PMID:19440620

Kabelác, Martin; Hobza, Pavel; Spirko, Vladimír

2009-03-12

161

Infrared spectra, vibrational assignment, and ab initio calculations for N-bromo-hexafluoro-2-propanimine.  

PubMed

The infrared spectra of gaseous and solid N-bromo-hexafluoro-2-propanimine, (CF(3))(2)CNBr, have been obtained from 2000 to 50 cm(-1). The vibrational assignment for the normal modes is proposed based on infrared band contours, group frequencies and normal coordinate calculations utilizing C(s) symmetry. The structural parameters have been obtained from ab initio MP2(full)/6-311+G(d,p) calculations employing the Gaussian-03 program. Additionally, the frequencies and potential energy distributions for the normal modes have been calculated with the MP2(full)/6-31G(d). All of these results are compared to the corresponding data for some similar molecules. PMID:22336042

Panikar, Savitha S; Guirgis, Gamil A; Sheehan, Tracie G; Durig, Douglas T; Durig, James R

2012-01-10

162

Selective calculation of high-intensity vibrations in molecular resonance Raman spectra  

NASA Astrophysics Data System (ADS)

We present an intensity-driven approach for the selective calculation of vibrational modes in molecular resonance Raman spectra. The method exploits the ideas of the mode-tracking algorithm [M. Reiher and J. Neugebauer, J. Chem. Phys. 118, 1634 (2003)] for the calculation of preselected molecular vibrations and of Heller's gradient approximation [Heller et al., J. Phys. Chem. 86, 1822 (1982)] for the estimation of resonance Raman intensities. The gradient approximation allows us to construct a basis vector for the subspace iteration carried out in the mode-tracking calculation, which corresponds to an artificial collective motion of the molecule that contains the entire intensity in the resonance Raman spectrum. Subsequently, the algorithm generates new basis vectors from which normal mode approximations are obtained. It is then possible to provide estimates for (i) the accuracy of the normal mode approximations and (ii) the intensity of these modes in the final resonance Raman spectrum. This approach is tested for the examples of uracil and a structural motif from the E colicin binding immunity protein Im7, in which a few aromatic amino acids dominate the resonance Raman spectrum at wavelengths larger than 240 nm.

Kiewisch, Karin; Neugebauer, Johannes; Reiher, Markus

2008-11-01

163

Structural, elastic, vibrational and electronic properties of amorphous Al2O3 from ab initio calculations  

NASA Astrophysics Data System (ADS)

First-principles molecular dynamics calculations of the structural, elastic, vibrational and electronic properties of amorphous Al2O3, in a system consisting of a supercell of 80 atoms, are reported. A detailed analysis of the interatomic correlations allows us to conclude that the short-range order is mainly composed of AlO4 tetrahedra, but, in contrast with previous results, also an important number of AlO6 octahedra and AlO5 units are present. The vibrational density of states presents two frequency bands, related to bond-bending and bond-stretching modes. It also shows other recognizable features present in similar amorphous oxides. We also present the calculation of elastic properties (bulk modulus and shear modulus). The calculated electronic structure of the material, including total and partial electronic density of states, charge distribution, electron localization function and the ionicity for each species, gives evidence of correlation between the ionicity and the coordination for each Al atom.

Davis, Sergio; Gutiérrez, Gonzalo

2011-12-01

164

On the number of significant mode-mode anharmonic couplings in vibrational calculations: Correlation-corrected vibrational self-consistent field treatment of di-, tri-, and tetrapeptides  

NASA Astrophysics Data System (ADS)

A computational study is made of the number of important anharmonic mode-mode couplings in the context of vibrational calculations for di-, tri-, and tetrapeptides. The method employed is the correlation-corrected vibrational self-consistent field (CC-VSCF) algorithm, which includes correlation effects between different vibrational modes. It is found that results of good accuracy can be obtained in calculations that include only N log N mode-mode coupling terms, where N is the number of modes. This simplification significantly accelerates CC-VSCF calculations for large molecules. A criterion based on the characteristics of the normal-mode displacements is employed to predict a priori unimportant coupling terms. The criterion is tested statistically using Spearman's rank correlation coefficient. The results are illustrated by calculations for several di-, tri-, and tetrapeptides using semiempirical PM3 potential surfaces. These results are analyzed and a statistical model for error estimation is given. The decrease in the number of included coupling from N2 to N log N opens possibilities of anharmonic vibrational calculations for large peptides.

Pele, Liat; Gerber, R. Benny

2008-04-01

165

Calculation of low-frequency vibrational modes of biologically important isomers  

NASA Astrophysics Data System (ADS)

In this paper we compare the value of different molecular modeling techniques for the prediction of vibrational modes, especially in the mid- and far-infrared region. There is a wide range of different levels of theory available for molecular modelling - the choice depending on the kind of system to be investigated. For our calculations we use different theoretical approaches such as Hartree-Fock and Density functional theory. We also compare the performances of two available electronic structure programs-Gamess-US and Gaussian03. As examples, we use two different retinoids - all-trans retinal and all-trans retinoic acid - derivatives of Vitamin A.

Jones, Inke; Rainsford, Tamath J.; Fischer, Bernd M.; Abbott, Derek

2007-12-01

166

Harmonic synchronization of nonlinear oscillators  

Microsoft Academic Search

The locking range of a harmonic synchronized oscillator is calculated, and it is shown to be proportional to the relative harmonic amplitude produced by the nonlinearity. For completeness a simple method is given for calculating the harmonic output produced.

I. Schmideg

1971-01-01

167

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

NASA Astrophysics Data System (ADS)

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.

Kubicki, J. D.

2008-12-01

168

Optimal basis states for a microscopic calculation of intrinsic vibrational wave functions of deformed rotational nuclei  

NASA Astrophysics Data System (ADS)

The primary achievement of the symplectic model is to give a realistic microscopic shell-model expression of the nuclear collective model. However, in applications of the model, one has to contend with the fact that its Hilbert spaces, like those of the shell model, are infinite dimensional. This means that truncation of the model Hilbert space to a finite-dimensional subspace is inevitable. Nevertheless, it is in principle possible to get results to any desired accuracy if a sequence of increasingly large, but finite-dimensional subspaces of the full Hilbert space can be determined so that truncation to the subspaces of the sequence leads to rapidly convergent results. We show in this paper that generator coordinate (also called coherent state) bases can be constructed and optimized to give extraordinarily rapid convergence. This makes it possible to perform accurate symplectic model calculations with realistic microscopic Hamiltonians by a method that is essentially an angular-momentum projected, multi-determinant, Hartree-Fock calculation for which powerful but highly practical methods, that make a minimal use of group theory, have been developed. It is shown that the techniques developed give a natural representation of the intrinsic states of rotational bands as beta- and/or gamma-vibrational wave functions. The techniques are illustrated by computation of beta-vibrational wave functions for the ground-state and one-phonon excited rotational bands of 8Be for a microscopic Hamiltonian with a Brink-Boeker two-body interaction.

Carvalho, M. J.; Rowe, D. J.; Karram, S.; Bahri, C.

2002-05-01

169

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

PubMed

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

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

2013-07-14

170

Numerical Analysis of Third Harmonic Overtone of Thickness-Shear Vibrations in SC-Cut Quartz Resonators.  

National Technical Information Service (NTIS)

Research on algorithms, strategies and problems associated with the numerical modeling of high frequency piezoelectric resonators was performed. The research was applied principally to SC-cut quartz crystal resonators vibrating at the third overtone of th...

Y. K. Yong

1995-01-01

171

Orbital-optimized coupled-electron pair theory and its analytic gradients: accurate equilibrium geometries, harmonic vibrational frequencies, and hydrogen transfer reactions.  

PubMed

Orbital-optimized coupled-electron pair theory [or simply "optimized CEPA(0)," OCEPA(0), for short] and its analytic energy gradients are presented. For variational optimization of the molecular orbitals for the OCEPA(0) method, a Lagrangian-based approach is used along with an orbital direct inversion of the iterative subspace algorithm. The cost of the method is comparable to that of CCSD [O(N(6)) scaling] for energy computations. However, for analytic gradient computations the OCEPA(0) method is only half as expensive as CCSD since there is no need to solve the ?2-amplitude equation for OCEPA(0). The performance of the OCEPA(0) method is compared with that of the canonical MP2, CEPA(0), CCSD, and CCSD(T) methods, for equilibrium geometries, harmonic vibrational frequencies, and hydrogen transfer reactions between radicals. For bond lengths of both closed and open-shell molecules, the OCEPA(0) method improves upon CEPA(0) and CCSD by 25%-43% and 38%-53%, respectively, with Dunning's cc-pCVQZ basis set. Especially for the open-shell test set, the performance of OCEPA(0) is comparable with that of CCSD(T) (?R is 0.0003 A? on average). For harmonic vibrational frequencies of closed-shell molecules, the OCEPA(0) method again outperforms CEPA(0) and CCSD by 33%-79% and 53%-79%, respectively. For harmonic vibrational frequencies of open-shell molecules, the mean absolute error (MAE) of the OCEPA(0) method (39 cm(-1)) is fortuitously even better than that of CCSD(T) (50 cm(-1)), while the MAEs of CEPA(0) (184 cm(-1)) and CCSD (84 cm(-1)) are considerably higher. For complete basis set estimates of hydrogen transfer reaction energies, the OCEPA(0) method again exhibits a substantially better performance than CEPA(0), providing a mean absolute error of 0.7 kcal mol(-1), which is more than 6 times lower than that of CEPA(0) (4.6 kcal mol(-1)), and comparing to MP2 (7.7 kcal mol(-1)) there is a more than 10-fold reduction in errors. Whereas the MAE for the CCSD method is only 0.1 kcal mol(-1) lower than that of OCEPA(0). Overall, the present application results indicate that the OCEPA(0) method is very promising not only for challenging open-shell systems but also for closed-shell molecules. PMID:23927240

Bozkaya, U?ur; Sherrill, C David

2013-08-01

172

Calculation of highly excited vibrational energy levels of CH3CN molecule by non-linear quantum theory  

Microsoft Academic Search

A three-parameter nonlinear dynamical model, i.e., the quantized discrete self-trapping equation, was used to calculate the highly excited CH stretching vibrational energy levels of liquid phase CH3CN molecule in the electronic ground state up to n=7. The calculated results show that the experimental energy levels can be well described by the model.

Zhu Jun; Gou Qing-quan

1999-01-01

173

Variational calculation of specific, highly excited vibrational states in DFCO: comparison with experimental data.  

PubMed

A stimulated emission pumping spectra of jet-cooled DFCO performed by Crane et al. (J. Mol. Spectrosc. 1997, 183, 273) has provided a great number of ro-vibrational lines up to 9000 cm(-1) of excitation energy. By combining a Jacobi-Wilson (JW) approach with a Davidson scheme, we calculate the lines provided by the experiment up to 9000 cm(-1) using an ab initio global potential energy surface (PES) developed by Kato et al. (J. Chem. Phys. 1997, 107, 6114). Comparisons between experimental and calculated data provide a critical test of the quality of the PES used. We show that the variational calculated energies can be efficiently corrected by taking into account the error observed for the A' fundamental transitions nu(i) (i = 1, ..., 5) and the first overtone 2nu(6). A detailed analysis of the eigenstates obtained by the calculation allows one to quantify the coupling between the different modes. Such an information is essential to understand and predict the energy flow through a DFCO molecule that is initially excited. PMID:17880188

Iung, Christophe; Pasin, Gauthier

2007-09-20

174

Structural and vibrational properties of VO2 from DFT and DFT+U calculations  

NASA Astrophysics Data System (ADS)

Vanadium dioxide (VO2) undergoes a metal-insulator transition (MIT) at 340,from a metallic, high-temperature rutile phase to a insulating, low-temperature monoclinic phase. In thin films, the extremely fast switching times (˜100 femtoseconds) of the MIT have led to many suggested device applications. Understanding the MIT driving mechanism and the long-debated importance of electronic correlation is important to these developments. We have computed the relaxed geometry and phonon frequencies using DFT and DFT+U for both phases of VO2. The dependence of vibrational mode frequencies and oscillator strengths on the Hubbard U parameter and their sensitivity to the Born effective charges in the insulating monoclinic phase will be reported. The calculated frequencies for U=5 eV are in good agreement with recent experimental infrared micro-spectroscopy measurements on single crystal platelets of VO2 footnotetextT. J. Huffman et al., PRB, submitted.. Our results indicate that strong electron-electron correlation must be included to describe the vibrational properties.

Walter, Eric J.; Krakauer, Henry; Huffman, Tyler J.; Xu, Peng; Qazilbash, M. M.

2013-03-01

175

Analyzing the vibrational signatures of thiophenol adsorbed on small gold clusters by DFT calculations.  

PubMed

Using density functional theory, we calculate the IR and Raman signatures of the thiophenol (TP) molecule adsorbed on gold clusters by mimicking the different types of adsorption sites, and we analyze these signatures by using advanced tools implemented into the pyvib2 program. First, we follow the evolution of the vibrational normal modes from the isolated TP molecule to those of TP adsorbed on different clusters to highlight the influence of the site of adsorption on the vibrational motions. The use of the overlap matrix between the modes enables mode permutations, mode mixings, and mode splittings to be highlighted, all of which depend not only on the adsorption but also on the type of cluster and its symmetry. Second, the IR and Raman signatures were analyzed by using group coupling matrices and atomic contribution patterns based on the Hug decomposition scheme. Key results include 1) the fact that Raman spectroscopy is more sensitive than IR spectroscopy with respect to the nature of the coordination site, 2) an IR criterion that distinguishes between on-top coordination (onefold coordinated) with respect to the bridge (twofold coordinated) and hexagonal close-packed hollow site coordination (threefold coordinated), and 3) the best agreement to the experimental Raman spectrum with regard to signatures in the 500 to 1200 cm(-1) region is obtained for bridged, twofold coordination. PMID:23592337

Tetsassi Feugmo, Conrard Giresse; Liégeois, Vincent

2013-04-16

176

Effects of large vibration amplitudes on the mode shapes and natural frequencies of thin elastic structures, Part 3: Fully clamped rectangular isotropic plates - measurements of the mode shape amplitude dependence and the spatial distribution of harmonic distortion  

Microsoft Academic Search

In this work, the amplitude dependence of the resonance frequency and the spatial distribution of the first and second harmonic components of the dynamic response of a fully clamped rectangular homogeneous plate have been investigated experimentally. By using electrodynamic point excitation at the center of the plate and a non-contacting optical vibration transducer for response measurement, the spatial distribution of

R. Benamar; M. M. K. Bennouna; R. G. White

1994-01-01

177

Mutual Co-Assignment of the Calculated Vibrational Frequencies in the Ground and Lowest Excited Electronic States  

NASA Astrophysics Data System (ADS)

The shifts of the molecular vibrational frequencies when going from the ground electronic state to the lowest excited electronic states pose some problems for the mutual co-assignment of the calculated vibrational frequencies in the different excited states. The trans-{C_2 O_2 F_2} shift of the frequency of the symmetrical ?(C=O) stretching vibration between the S_0 and T_1 is 373 wn. The feasibility of mutual co-assignments of the vibrational frequencies in these electronic states has been demonstrated for trans-{C_2 O_2 F_2}. Matrices analogous to the Duschinsky matrix were used to juxtapose the a_g vibrational frequencies of this molecule calculated at the CASPT2/cc-pVTZ level in the ground S_0 and excited triplet T_1 and singlet S_1 electronic states. The analog of the Duschinsky matrix D was obtained for this molecule using the equation D = (L_{I})^{-1} L_{II} where L_{I} and L_{II} are the matrices of the vibrational modes (normalized atomic displacements) obtained by solving the vibrational problems for the S_0 and T_1 electronic states, respectively. Choosing the dominant elements in columns of the D matrix and permuting these columns to arrange these elements along the diagonal of the transformed matrix D^* makes it possible to establish the correct mutual co-assignments of the calculated a_g vibrational frequencies of the trans-{C_2 O_2 F_2} molecule in the S_0 and T_1 electronic states. The analogous procedure was performed for the trans-{C_2 O_2 F_2} molecule in the T_1 and S_1 excited electronic states. The recent reassignments of the ?b{2} and ?b{3} calculated vibrational frequencies in the trans-{C_2 O_2 F_2} molecule in the ground state were also obtained for the triplet T_1 and singlet S_1 excited electronic states. The approach set forth in this text makes it possible to juxtapose the calculated vibrational frequencies of the same molecule in the different electronic states and to refine the assignments of these frequencies. This is essential in correctly analyzing the vibronic spectra of a molecule under investigation. F. Duschinsky, Acta Physicochim. URSS, 7 (4), 551-566 (1937).

Panchenko, Yurii N.

2013-06-01

178

Vibrational investigation, molecular orbital studies and molecular electrostatic potential map analysis on 3-chlorobenzoic acid using hybrid computational calculations.  

PubMed

The FT-IR and FT-Raman spectra of 3-chlorobenzoic acid (3CBA) are recorded in the liquid state. The fundamental vibrational frequencies, intensity of vibrational bands and the optimized geometrical parameters of the compound are evaluated using HF and DFT (LSDA/B3LYP/B3PW91/MPW1PW91) methods with 6-311+G(d,p) basis set. The theoretical wave numbers are scaled down and compared with the experimental values which showed very good agreement. Comparison of stimulated spectra with the experimental spectra provides important information about the ability of the hybrid computational method to describe the vibrational modes. The HOMO, LUMO, chemical hardness (?), chemical potential (?), electrophilicity values (?) and maximum amount of electronic charge transfer (?N(max)) are calculated. The molecular electrostatic potential (MESP) is calculated and the corresponding graphs are drawn. Some thermodynamic parameters and physico-chemical properties are calculated and discussed. PMID:21993254

Ramalingam, S; Babu, P David Suresh; Periandy, S; Fereyduni, E

2011-09-20

179

Harmonic diversity and determining factors of radial forces in external rotor permanent magnet synchronous motors with concentrated windings  

Microsoft Academic Search

In external rotor permanent magnet synchronous motors, also the higher frequency harmonics of the radial forces generate considerable resonant vibrations and acoustic noise. Therefore, diversity of spatial and especially frequency harmonic ordinal numbers of representative slot and pole number combinations are derived analytically with open-circuit and under load. Amplitudes of radial force waves are calculated by means of the finite

Jens Krotsch; Bernhard Piepenbreier

2010-01-01

180

Collocation method for calculating vibrational bound states of molecular systems: with application to Ar--HCl  

SciTech Connect

The ability of the collocation method to calculate vibrational bound states of molecules is investigated. The technique is simpler to implement than conventional variational methods; no integration over the basis functions is involved. We apply the method to the weakly bound complex Ar--HCl, a real multidimensional system of considerable physical interest, and find the procedure to be of equivalent accuracy to the corresponding variational approach at all times. This confirms the conclusions of our previous studies on one-dimensional test problems (W. Yang and A. C. Peet, Chem. Phys. Lett. (in press)). Both low lying and highly excited states are examined and the conclusions hold even for levels very close to the dissociation limit. A test of the wave functions obtained also finds these to be of good accuracy and very similar to the ones given by the variational procedure.

Peet, A.C.; Yang, W.

1989-02-01

181

Structures and vibrational frequencies of 2-naphthoic acid and 6-bromo-2-naphthoic acid based on density functional theory calculations.  

PubMed

The solid phase mid FTIR and FT Raman spectra of 2-naphthoic acid (NA) and 6-bromo-2-naphthoic acid (BNA) have been recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The fundamental vibrational frequencies and intensities of the vibrational bands were evaluated using density functional theory (DFT) using standard B3LYP method and 6-311+G** basis set combinations. The vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. PMID:17822949

Krishnakumar, V; Mathammal, R; Muthunatesan, S

2007-07-28

182

Guanidinium perchlorate ferroelectric crystal. Study of vibrational properties based on experimental measurements and theoretical calculations  

NASA Astrophysics Data System (ADS)

The infrared and Raman spectra of guanidinium perchlorate were measured at room temperature. The spectra are discussed with the framework of literature X-ray structure in relation to internal hydrogen bond network. For complete vibrational analysis the theoretical calculation of both infrared and Raman spectra in DFT approach were performed. The clear-cut assignment of observed bands was made on the basis of PED analysis. On the basis of theoretical studies the electrostatic charges and energies of HOMO and LUMO orbitals were obtained. Additionally the first order hyperpolarizability of investigated molecule was calculated. The obtained results are in good agreement with literature data, but according to performed calculation the specific damping of ? hyperpolarizability in unit cell (comparable with isolated molecule) is observed. To explain in detail phase transitions phenomena (at ca. 452 and 454 K) described in literature the temperature dependent infrared powder spectra were recorded. The temperature dependencies of bands position and intensities for titled crystal in the range 11-480 K are analyzed.

Drozd, M.; Dudzic, D.

2013-11-01

183

Structural, vibrational, electronic and NMR spectral analysis of 3-chloro-6-methoxypyridazine by DFT calculations  

NASA Astrophysics Data System (ADS)

In this work, the FT-Raman and FT-Infrared spectra of 3-chloro-6-methoxypyridazine sample were measured to elucidate the spectroscopic properties of title molecule in the spectral range of 3500-50 cm-1 and 4000-400 cm-1, respectively. The molecular geometry and vibrational frequencies of 3-chloro-6-methoxypyridazine in the ground state were calculated using the DFT/B3LYP/6-31G(d),6-311G(d,p) level. The recorded FT-IR and FT-Raman spectral measurements favor the calculated structural parameters which are further supported by spectral simulation. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The UV-Visible absorption spectrum of the compound that dissolved in methanol was recorded in the range of 800-200 nm. The formation of hydrogen bond and the most possible interaction are explained using natural bond orbital (NBO) analysis. The isotropic chemical shift computed by 13C and 1H NMR analysis also shows good agreement with experimental observations. In addition, the molecular electrostatic potential (MEP) and frontier molecular orbitals (FMOs) analysis of the title compound were investigated using theoretical calculations.

Vijaya Chamundeeswari, S. P.; James Jebaseelan Samuel, E.; Sundaraganesan, N.

2013-06-01

184

Ab initio anharmonic calculations of vibrational frequencies of benzene by means of efficient construction of potential energy functions  

NASA Astrophysics Data System (ADS)

An efficient technique constructing anharmonic potential energy functions was applied to ab initio vibrational analysis of benzene. Anharmonic potentials including the 6-order terms, much higher than the full quartic force field, were automatically generated by a second-order algorithm using the scaled hypersphere search method, and vibrational calculations were performed at the level of VQDPT[1+2]. In comparison with previously reported anharmonic calculations, the present approach gave an excellent ab initio result for in-plane modes including the b 2u so called Kekulé mode. Characteristic properties of various approaches were discussed in connection with the anharmonic effects and the strong vibronic effects.

Ohno, Koichi; Maeda, Satoshi

2011-02-01

185

Two-Dimensional Spectroscopy for Harmonic Vibrational Modes with Nonlinear System-Bath Interactions. II. Gaussian-Markovian Case  

NASA Astrophysics Data System (ADS)

The relaxation processes in a quantum system nonlinearly coupled to a harmonic Gaussian-Markovian heat bath are investigated by the quantum Fokker-Planck equation in the hierarchy form. This model describes frequency fluctuations in the quantum system with an arbitrary correlation time and thus bridges the gap between the Brownian oscillator model and the stochastic model by Anderson and Kubo. The effects of the finite correlation time and the system-bath coupling strength are studied for a harmonic model system by numerically integrating the equation of motion. The one-time correlation function of the system coordinate, which is measured in conventional Raman and infrared absorption experiments, already reflects the inhomogeneous character of the relaxation process. The finite correlation time of the frequency fluctuations, however, is directly evident only in the two- and three-time correlation function as probed by multidimensional spectroscopic techniques such as the Raman echo and the fifth-order 2D Raman experiment.

Tanimura, Yoshitaka; Steffen, Thomas

2000-12-01

186

Flexural vibrations of a thin circular elastic inclusion in an unbounded body under the action of a plane harmonic wave  

Microsoft Academic Search

The interaction of a plane harmonic longitudinal wave with a thin circular elastic inclusion is considered. The wave front\\u000a is assumed to be parallel to the inclusion plane. Since the inclusion is thin, the matrix-inclusion interface conditions (perfect\\u000a bonding) are formulated on the mid-plane of the inclusion. The bending displacements of the inclusion are determined from\\u000a the bending equation for

L. V. Vakhonina; V. G. Popov

2008-01-01

187

Conformational stability, r0 structural parameters, ab initio calculations, and vibrational assignment for silacyclopentane  

NASA Astrophysics Data System (ADS)

The infrared spectra (3500 50 cm-1) of the gas and solid and the Raman spectrum (3200 30 cm-1) of liquid silacyclopentane, c-C4H8SiH2, have been recorded. Additionally the infrared spectrum (3200 400 cm-1) of liquid xenon solutions has been recorded at -65 and -95 °C. In all of the physical states only one conformer was detected which is the twisted C2 form. The conformational energetics have been calculated with the Mřller Plesset perturbation method to the second order, (MP2(full)) as well as with density functional theory by the B3LYP method utilizing a variety of basis sets. All of these calculations predict only one stable conformer i.e. the C2 form with an average barrier to planarity of 2558 cm-1 (30.60 kJ/mol) from the MP2 calculations and a significantly lower value of 1918 cm-1 (22.95 kJ/mol) from the DFT calculations with neither calculations being significantly effect by inclusion of diffuse functions. From the isolated SiH frequency from the SiHD isotopomer the SiH distance was calculated to be 1.486(3) Ĺ. By utilizing the previously reported microwave rotational constants for three isotopomers (28Si,29Si, and 28Si-d2) combined with the structural parameters predicted from the MP2(full)/6-311 + G(d,p) calculations, adjusted r0 structural parameters have been obtained. The determined heavy atom distances are: r0(SiC) = 1.890(5); r0(C2C4) and (C3C5) = 1.547(5); r0(C4C5) = 1. 535(5) Ĺ and the angles in degrees: ?CSiC = 95.9(5)°; ?SiCC = 103.3(5)°; ?CCC = 107.9(5)° with the two dihedral angles ?SiCCC = -38.3(3)° and ?CCCC = 52.4(3)°. A complete vibrational assignment is given for the twisted C2 conformer for the normal species and the Si-d2 isotopomer which are supported by normal coordinate calculations utilizing scaled force constants from ab initio MP2(full)/6-31G(d) calculations. The results of these spectroscopic and theoretical studies are discussed and compared to the corresponding results for some similar molecules.

Guirgis, Gamil A.; El Defrawy, Ahmed M.; Gounev, Todor K.; Soliman, Mamdouh S.; Durig, James R.

2007-04-01

188

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

NASA Astrophysics Data System (ADS)

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

Takahashi, Masae; Ishikawa, Yoichi; Ito, Hiromasa

2013-03-01

189

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

SciTech Connect

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.

Carter, S.; Bowman, J.M.

2000-03-23

190

Vibrational spectra, DFT quantum chemical calculations and conformational analysis of P-iodoanisole  

NASA Astrophysics Data System (ADS)

The solid phase FT-IR and FT-Raman spectra of P-iodoanisole (P-IA) have been recorded in the regions 400-4000 and 50-4000 cm-1, respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by ab initio (HF) and density functional theory (B3LYP) methods with LanL2DZ as basis set. The potential energy surface scan for the selected dihedral angle of P-IA has been performed to identify stable conformer. The optimized structure parameters and vibrational wavenumbers of stable conformer have been predicted by density functional B3LYP method with LanL2DZ (with effective core potential representations of electrons near the nuclei for post-third row atoms) basis set. The nucleophilic and electrophilic sites obtained from the molecular electrostatic potential (MEP) surface were calculated. The temperature dependence of thermodynamic properties has been analyzed. Several thermodynamic parameters have been calculated using B3LYP with LanL2DZ basis set.

Arivazhagan, M.; Anitha Rexalin, D.; Geethapriya, J.

2013-09-01

191

Vibrational spectra, DFT quantum chemical calculations and conformational analysis of P-iodoanisole.  

PubMed

The solid phase FT-IR and FT-Raman spectra of P-iodoanisole (P-IA) have been recorded in the regions 400-4000 and 50-4000 cm(-1), respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by ab initio (HF) and density functional theory (B3LYP) methods with LanL2DZ as basis set. The potential energy surface scan for the selected dihedral angle of P-IA has been performed to identify stable conformer. The optimized structure parameters and vibrational wavenumbers of stable conformer have been predicted by density functional B3LYP method with LanL2DZ (with effective core potential representations of electrons near the nuclei for post-third row atoms) basis set. The nucleophilic and electrophilic sites obtained from the molecular electrostatic potential (MEP) surface were calculated. The temperature dependence of thermodynamic properties has been analyzed. Several thermodynamic parameters have been calculated using B3LYP with LanL2DZ basis set. PMID:23727676

Arivazhagan, M; Anitha Rexalin, D; Geethapriya, J

2013-05-07

192

Quantum chemical calculations, vibrational studies, HOMO-LUMO and NBO/NLMO analysis of 2-bromo-5-nitrothiazole  

NASA Astrophysics Data System (ADS)

The complete vibrational assignment and analysis of the fundamental modes of 2-bromo-5-nitrothiazole (BNT) was carried out using the experimental FTIR and FT-Raman 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 ab initio HF and DFT-B3LYP gradient calculations employing 6-311++G(d,p) basis set. Thermodynamic properties like entropy, heat capacity and zero point energy have been calculated for the molecule. 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 electric dipole moment and first hyperpolarizability of BNT have been computed using B3LYP quantum chemical calculation.

Gobinath, E.; Xavier, R. John

2013-03-01

193

Lattice vibrations and thermal properties of carbon nitride with defect ZnS structure from first-principles calculations  

Microsoft Academic Search

The phonon spectrum of C3N4 with defect zincblende-type structure (?-C3N4) was calculated by density functional theory(DFT) techniques. The results permit an assessment of important mechanical and thermodynamical properties such as the bulk modulus, lattice specific heat, vibration energy, thermal expansion coefficient, and thermal Grneisen parameter. The thermal Grneisen parameter of ?-C3N4 is calculated to be about 1.19 at 300K, comparable

C. M. Fang; G. A. de Wijs

2004-01-01

194

A variational calculation of weakly bound rotational-vibrational states of the mesic molecules ddmu and dtmu  

Microsoft Academic Search

Variational calculations of energy levels, of ?Jv and lambda-factors of weakly bound rotational-vibrational states (J=1, v=1) of the mesic molecules ddmu and dtmu, which are of main interest for recent muon-catalysed fusion experiments are performed. A set of about 2000 basis functions has been used in calculations which has enabled us to obtain the following extrapolated values: ?11 (ddmu) =

V. I. Korobov; I. V. Puzynin; S. I. Vinitsky

1987-01-01

195

On quadrupole vibrations in nearly spherical nuclei  

NASA Astrophysics Data System (ADS)

A new understanding of low-lying quadrupole vibrations in nuclei is emerging through lifetime measurements performed with fast neutrons at the accelerator laboratory of the University of Kentucky in combination with high-sensitivity measurements with other probes. In the stable cadmium nuclei, which have long been considered to be the best examples of vibrational behavior, we find that many E2 transition probabilities are well below harmonic vibrator expectations, and the B(E2)s cannot be explained with calculations incorporating configuration mixing between vibrational phonon states and intruder excitations. These data place severe limits on the collective models, and it is suggested that the low-lying levels of the Cd isotopes may not be of vibrational origin. An additional example of an apparent quadrupole vibrational nucleus, 62Ni, is considered.

Yates, S. W.

2012-09-01

196

Franck-Condon transitions in a system with large-amplitude anharmonic vibrations coupled to a harmonic-oscillator bath: Application to the C 1s photoelectron spectrum of ethanol  

SciTech Connect

A vibrational adiabatic approach to Franck-Condon analysis is presented for systems with a few highly displaced oscillators coupled to a bath of harmonic oscillators. The model reduces the many-coupled-oscillator problem to few-body problems, albeit with corrections due to coupling to harmonic modes. The theory is applied with very good results to the carbon 1s photoelectron spectrum of ethanol, which is strongly influenced by change in conformation from gauche to anti when ethanol is ionized at the methyl site.

Abu-samha, M.; Boerve, K. J. [Department of Chemistry, University of Bergen, NO-5007 Bergen (Norway)

2006-10-15

197

Reduction of electromagnetic force harmonics in asynchronous traction motor by adapting the rotor slot number  

SciTech Connect

The harmonics in electromagnetic force are source of the mechanical vibration and the audible noise in an asynchronous traction motor. This paper describes an approach to reduce the force harmonics by changing the rotor slot number. Both the radial and tangential forces acting on the stator teeth are calculated by Maxwell stress tenser and their time harmonics are examined by the discrete Fourier decomposition. As a result, the optimal slot number of the rotor to reduce or eliminate the specific force harmonics is determined.

Kim, B.T.; Kwon, B.I.; Park, S.C.

1999-09-01

198

Calculation of the Elastic Tube Bending Vibrations Using the Carbine K 98 as an Example Berechnung der Elastischen Rohrbiegeschwingungen Am Beispiel des Karabiners K 98.  

National Technical Information Service (NTIS)

The vertical elastic bending vibrations were calculated for the K 98 carbine barrel (caliber 7.62 mm) during projectile transit. The band was assumed to be fixed at one end. The calculation was based on vibration excitation by the projectile mass during t...

K. Wolf R. Heiser

1975-01-01

199

Predictive calculation of the lattice thermal conductivity with temperature-dependent vibrational parameters  

NASA Astrophysics Data System (ADS)

This paper presents a predictive model for the lattice thermal conductivity. The model is based on Callaway's solution to the Boltzmann equation for phonons which discriminates between the natures of the resistive and nonresistive phonon processes. However, the present model uses temperature-dependent lattice vibrational parameters and sound group velocities calculated on the basis of a dynamical matrix. No adjustment to thermal conductivity measurements is required. The model requires only the material mechanical properties as inputs to yield the material thermal conductivity as a function of temperature. A precise transmission probability function is introduced in the model in order to widen its application for the cases where interfaces are present. The importance of all the features of the developed model is demonstrated clearly with reference to reported data regarding the effects of surface orientation and isotope composition in single crystals, the effect of alloy composition in alloys, and the effect of grains boundaries in polycrystals. Namely, the developed model accounts for (i) the effects of surface orientation and isotope composition on the thermal conductivity of silicon and germanium single crystals, (ii) the effect of alloy composition on the thermal conductivity of silicon-germanium alloys, and (iii) the effect of phonon scattering at grains boundaries on the thermal conductivity of polycrystalline silicon.

Alameh, Z.; Kazan, M.

2012-12-01

200

A unifying model for non-adiabatic coupling at metallic surfaces beyond the local harmonic approximation: from vibrational relaxation to scanning tunneling microscopy.  

PubMed

A model for treating excitation and relaxation of adsorbates at metallic surfaces induced by non-adiabatic coupling is developed. The derivation is based on the concept of resonant electron transfer, where the adsorbate serves as a molecular bridge for the inelastic transition between an electron source and a sink. In this picture, energy relaxation and scanning tunneling microscopy (STM) at metallic surfaces are treated on an equal footing as a quasi-thermal process. The model goes beyond the local harmonic approximation and allows for an unbiased description of floppy systems with multiple potential wells. Further, the limitation of the product ansatz for the vibronic wave function to include the position-dependence of the non-adiabatic couplings is avoided by explicitly enforcing detailed balance. The theory is applied to the excitation of hydrogen on palladium, which has multiple local potential minima connected by low energy barriers. The main aspects investigated are the lifetimes of adsorbate vibrations in different adsorption sites, as well as the dependence of the excitation, response, and transfer rates on an applied potential bias. The excitation and relaxation simulations reveal intricate population dynamics that depart significantly from the simplistic tunneling model in a truncated harmonic potential. In particular, the population decay from an initially occupied local minimum induced by the contact with an STM tip is found to be better described by a double exponential. The two rates are interpreted as a response to the system perturbation and a transfer rate following the perturbation. The transfer rate is found to obey a power law, as was the case in previous experimental and theoretical work. PMID:23822226

Tremblay, Jean Christophe

2013-06-28

201

MR harmonic quad study  

SciTech Connect

To understand the effect of Main Ring harmonic quadruple correctors. Previous data taken with the harmonic quads did not agree well with the SYNCH calculation. The ultimate goal of this study was to be able to change the harmonic quads and verify the changes in lattice function.

Yang, M.-J.; /Fermilab

1995-01-01

202

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)

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.

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

2011-12-01

203

Seminar on Ship Vibration.  

National Technical Information Service (NTIS)

Contents: Pressure fluctuations induced by a cavitating propeller; Experiences in defining propeller induced hull forces; Ship vibration calculations; Current trends in vibration calculation methods; Ship vibration measurements; State of the art of ship's...

1982-01-01

204

Exploring the correlation between network structure and electron binding energy in the (H(2)O)(7)(-) cluster through isomer-photoselected vibrational predissociation spectroscopy and ab initio calculations: addressing complexity beyond types I-III.  

PubMed

We report a combined photoelectron and vibrational spectroscopy study of the (H(2)O)(7)(-) cluster anions in order to correlate structural changes with the observed differences in electron binding energies of the various isomers. Photoelectron spectra of the (H(2)O)(7)(-) . Ar(m) clusters are obtained over the range of m=0-10. These spectra reveal the formation of a new isomer (I') for m>5, the electron binding energy of which is about 0.15 eV higher than that of the type I form previously reported to be the highest binding energy species [Coe et al., J. Chem. Phys. 92, 3980 (1990)]. Isomer-selective vibrational predissociation spectra are obtained using both the Ar dependence of the isomer distribution and photochemical depopulation of the more weakly (electron) binding isomers. The likely structures of the isomers at play are identified with the aid of electronic structure calculations, and the electron binding energies, as well as harmonic vibrational spectra, are calculated for 28 low-lying forms for comparison with the experimental results. The HOH bending spectrum of the low binding type II form is dominated by a band that is moderately redshifted relative to the bending origin of the bare water molecule. Calculations trace this feature primarily to the bending vibration localized on a water molecule in which a dangling H atom points toward the electron cloud. Both higher binding forms (I and I') display the characteristic patterns in the bending and OH stretching regions signaling electron attachment primarily to a water molecule in an AA binding site, a persistent motif found in non-isomer-selective spectra of the clusters up to (H(2)O)(50)(-). PMID:18345895

Roscioli, Joseph R; Hammer, Nathan I; Johnson, Mark A; Diri, Kadir; Jordan, Kenneth D

2008-03-14

205

Global Calculations Using Potential Functions and Effective Hamiltonian Models for Vibration-Rotation Spectroscopy and Dynamics of Small Polyatomic Molecules  

Microsoft Academic Search

It has become increasingly common to use accurate potential energy surfaces and dipole moment surfaces for predictions and assignment of high-resolution vibration-rotation molecular spectra. These surfaces are obtained either from high-level ab initio electronic structure calculations or from a direct fit to experimental spectroscopic data. The talk will continue a discussion of some recent advances in the domain of the

Vladimir Tuyterev

2010-01-01

206

Calculation of conformations and vibrational spectra of a monomeric fragment of the 2,6-carboxymethyl cellulose molecule  

Microsoft Academic Search

A theoretical conformational analysis has been carried out for the side substituents of a fragment of the molecule for 2,6-carboxymethyl cellulose (a water-soluble cellulose ether), and the frequencies and the potential energy distribution of the normal vibrations have been calculated for the most stable conformers of the ether groups of this fragment in the approximation of the molecular mechanics method.

V. M. Andrianov

2007-01-01

207

Calculation of conformations and vibrational spectra of a monomeric fragment of the 2,6-carboxymethyl cellulose molecule  

Microsoft Academic Search

A theoretical conformational analysis has been carried out for the side substituents of a fragment of the molecule for 2,6-carboxymethyl\\u000a cellulose (a water-soluble cellulose ether), and the frequencies and the potential energy distribution of the normal vibrations\\u000a have been calculated for the most stable conformers of the ether groups of this fragment in the approximation of the molecular\\u000a mechanics method.

V. M. Andrianov

2007-01-01

208

Calculation of conformations and vibrational spectra of a monomeric fragment of the 2,6-carboxymethyl cellulose molecule  

NASA Astrophysics Data System (ADS)

A theoretical conformational analysis has been carried out for the side substituents of a fragment of the molecule for 2,6-carboxymethyl cellulose (a water-soluble cellulose ether), and the frequencies and the potential energy distribution of the normal vibrations have been calculated for the most stable conformers of the ether groups of this fragment in the approximation of the molecular mechanics method. It has been shown that the most stable conformers are those that have the conformations gg, t, g-, g-, g--for the groups of atoms on the bonds C5-C6, C6-O6, C13-O6, C10-C13, C10-O9 and the conformations g+g-, g+, g-, g-; g+g-, g-, g-, g-; g+g-, g-, g+, t for the groups of atoms on the bonds C2-O2, C11-O2, C7-C11, C7-O8. Comparative analysis of the calculated frequencies and the potential energy distribution of the normal vibrations for 13 of the most stable conformers showed, as in the case of the 2,6-hydroxyethyl cellulose molecule, that the frequencies and modes of the normal vibrations are highly sensitive to conformational transitions in the analyzed spectral region (800-1500 cm-1). The characteristic patterns for the change in the frequencies and modes of the normal vibrations have been established in connection with conformational transitions within both side substituents. The observed conformational lability of the bulky substituents in the cellulose ether molecules and its manifestations in the vibrational spectrum provide a basis for hypothesizing that one of the major mechanisms for the process of their thermal gelation in aqueous solutions is conformational transitions within these substituents.

Andrianov, V. M.

2007-01-01

209

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

210

Harmonic and Anharmonic Properties of Diamond Structure Crystals with Application to the Calculation of the Thermal Expansion of Silicon.  

National Technical Information Service (NTIS)

Silicon has interesting harmonic and anharmonic properties such as the low lying transverse acoustic modes at the X and L points of the Brillouin zone, negative Gruneisen parameters, negative thermal expansion and anomalous acoustic attenuation. In an att...

K. H. Wanser

1981-01-01

211

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)

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).

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

2011-11-01

212

Quantum Calculations of Quenching of Vibrationally Excited OH in Collisions With Atomic Oxygen  

NASA Astrophysics Data System (ADS)

Reaction between atomic hydrogen and ozone is an important source of vibrationally excited OH in the mesosphere. Radiative decay of vibrationally excited OH competes with collisional quenching by atomic and molecular oxygen and to a lesser extent by molecular nitrogen. Here we present the first explicit quantum mechanical investigation of quenching of vibrationally excited OH(v=1) by collisions with atomic oxygen. We explore both non-reactive quenching to OH(v=0) and reactive collisions leading to H+O2. It is found that the branching between reactive and non-reactive channels is strongly influenced by long-range dipole-quadrupole forces in the O+OH channel. The computed results are found to be in close agreement with available experimental results. This work was supported by NSF grant ATM-0635715.

Naduvalath, B.; Juanes-Marcos, J.; Quéméner, G.; Kendrick, B. K.

2011-12-01

213

Ground vibration due to railway traffic—The calculation of the effects of moving static loads and their experimental verification  

NASA Astrophysics Data System (ADS)

The propagation of waves through homogeneous or layered soil is calculated based on half-space theory. The moving dynamic loads of a train are approximated by fixed dynamic loads and the wave field can be calculated if the spectrum of the dynamic train loads is known. In addition to this dynamic wave field, there are three different components at three different frequency ranges which are caused by the passage of the static loads:the regular static component at low frequencies,the irregular static component at medium frequencies,the sleeper-passing component at high frequencies. For each of these components, an approximate solution is presented. The calculated wave field is compared with measurements of different trains at different sites. The measurement of impulse and harmonic point load excitation verifies the soil dynamic base of the method.

Auersch, L.

2006-06-01

214

Calculation of the even harmonics of emf in the winding of a ring core magnetized by an external constant field, with magnetic hysteresis taken into account  

SciTech Connect

The calculation of the even harmonics of electromotive force in the secondary winding of a ferromagnetic ring core or a core extended in one direction, having a closed magnetic circuit in relation to the magnetic excitation flux and being magnetized in the plane of the core (ring) by a weak magnetic field, is carried out taking into account magnetic hysteresis and using the criterion of physical similarity.

Ponomarev, Yu.V.

1988-09-01

215

Molecular and vibrational structure of 2,4-dinitrophenol: FT-IR, FT-Raman and quantum chemical calculations  

NASA Astrophysics Data System (ADS)

The molecular vibrations of 2,4-dinitrophenol (DNP) were investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopies. In parallel, semiempirical, ab initio and various density functional theory (DFT) methods are used to determine the geometrical, energetic and vibrational characteristics of DNP. Both the experimental and theoretical data suggest a rather strong intramolecular H-bond (HB) involving the hydroxyl and its neighbor nitro group. Semiempirical PM3 and ab initio methods fail to describe the HB while among different exchange and correlation functionals used in conjunction with DFT methods, only the B3LYP combination is able to quantitatively reproduce the effects of intramolecular HB, as reflected in FT-IR and FT-Raman spectra. The vibrational experimental bands were assigned to normal modes on the basis of DFT calculations at the B3LYP/6-31G(d) and B3LYP/6-311G(df,p) levels of theory and by comparison with vibrational spectra of phenol, nitrobenzene, 2-nitrophenol and p-nitrophenol. The second nitro group brings a large atomic charge to the phenol ring, especially on C4 atom and this is mainly reflected in frequency sequence and intensity pattern of some ?(CC) vibrations with ?(NO 2) symmetric stretch contributions. The characteristic marker IR bands of DNP are discussed, and the intensities of several bands have been explained. It is also shown that in spite of its simplicity, AM1 semiempirical method is able to give surprisingly good agreement with experiment, especially for hydrogen bonding parameters in DNP.

Chi?, Vasile

2004-05-01

216

Vibrational dynamics of the H5+ and its isotopologues from multiconfiguration time-dependent Hartree calculations  

NASA Astrophysics Data System (ADS)

Full-dimensional multiconfiguration time-dependent Hartree (MCTDH) computations are reported for the vibrational states of the H5+ and its H4D+, H3D2+, H2D3+, HD4+, D5+ isotopologues employing two recent analytical potential energy surfaces of Xie et al. [J. Chem. Phys. 122, 224307 (2005)] and Aguado et al. [J. Chem. Phys. 133, 024306 (2010)]. The potential energy operators are constructed using the n-mode representation adapted to a four-combined mode cluster expansion, including up to seven-dimensional grids, chosen adequately to take advantage in representing the MCTDH wavefunction. An error analysis is performed to quantify the convergence of the potential expansion to reproduce the reference surfaces at the energies of interest. An extensive analysis of the vibrational ground state properties of these isotopes and comparison with the reference diffusion Monte Carlo results by Acioli et al. [J. Chem. Phys. 128, 104318 (2008)] are presented. It is found that these systems are highly delocalized, interconverting between equivalent minima through rotation and internal proton transfer motions even at their vibrational ground state. Isotopic substitution affects the zero-point energy and structure, showing preference in the arrangements of the H and D within the mixed clusters, and the most stable conformers of each isotopomer are the ones with the H in the central position. Vibrational excited states are also computed and by comparing the energies and structures predicted from the two surfaces, the effect of the potential topology on them is discussed.

Valdés, Álvaro; Prosmiti, Rita; Delgado-Barrio, Gerardo

2012-12-01

217

DFT calculations and vibrational (FT-IR, FT-Raman) spectra on an uracilyl-pyridinium salt  

NASA Astrophysics Data System (ADS)

In the present article we have studied the structural and vibrational properties of the N-protonated derivative of a cross-conjugated heterocyclic mesomeric betaine formed by an uracilyl and a dimethylamino substituted pyridinium group. Fourier transform infrared and Raman spectra were recorded from solid samples. Quantum chemistry density functional theory calculations were performed at the B3PW91/6-31G?? level. Geometrical parameters, charge distribution and natural bond orders were calculated for the ground-state minimum energy structure. The optimized geometry was found twisted with respect to the two aromatic planes. The pyridinium ring presents a quinoid structure, while the uracilyl ring only presents a localized double-bond, which is far from the carbonyl groups. The molecule is strongly polar along the longest molecular axis, being largely originated by the charge separation between the heterocycles. A force field and normal coordinate calculation was performed in order to correctly assign the measured infrared and Raman bands. Assignments suggest the existence of centro-symmetrical structures in solid state bonded by the CO and N H groups of the uracilyl ring. The calculated force constants in vibrational internal coordinates are in agreement with the structural parameters.

Schmidt, A.; Lindner, A. S.; Ramírez, F. J.

2007-05-01

218

Vibrational dynamics of a trinuclear oxo-bridged iron complex as studied by nuclear inelastic scattering, Mössbauer spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

We have applied nuclear inelastic scattering (NIS) and computational predictions based on density functional theory (DFT) to explore the vibrational dynamics of 57Fe in a trinuclear oxo-bridged iron(III) complex. Quantitative comparison of the experimentally measured vibrational dynamics of the Mössbauer nuclei 57Fe, with normal mode analysis, calculated via quantum chemical calculation based on DFT methods generally yields a good overall agreement and enables the assignment of Fe vibrational modes. The oxidation and spin state of the complex were determined by 57Fe Mössbauer spectroscopy.

Rajagopalan, S.; Asthalter, T.; Rabe, V.; Laschat, S.; Rauhut, G.; Roduner, E.

2010-03-01

219

Vibrational dynamics of the H5(+) and its isotopologues from multiconfiguration time-dependent Hartree calculations.  

PubMed

Full-dimensional multiconfiguration time-dependent Hartree (MCTDH) computations are reported for the vibrational states of the H(5)(+) and its H(4)D(+), H(3)D(2)(+), H(2)D(3)(+), HD(4)(+), D(5)(+) isotopologues employing two recent analytical potential energy surfaces of Xie et al. [J. Chem. Phys. 122, 224307 (2005)] and Aguado et al. [J. Chem. Phys. 133, 024306 (2010)]. The potential energy operators are constructed using the n-mode representation adapted to a four-combined mode cluster expansion, including up to seven-dimensional grids, chosen adequately to take advantage in representing the MCTDH wavefunction. An error analysis is performed to quantify the convergence of the potential expansion to reproduce the reference surfaces at the energies of interest. An extensive analysis of the vibrational ground state properties of these isotopes and comparison with the reference diffusion Monte Carlo results by Acioli et al. [J. Chem. Phys. 128, 104318 (2008)] are presented. It is found that these systems are highly delocalized, interconverting between equivalent minima through rotation and internal proton transfer motions even at their vibrational ground state. Isotopic substitution affects the zero-point energy and structure, showing preference in the arrangements of the H and D within the mixed clusters, and the most stable conformers of each isotopomer are the ones with the H in the central position. Vibrational excited states are also computed and by comparing the energies and structures predicted from the two surfaces, the effect of the potential topology on them is discussed. PMID:23231232

Valdés, Álvaro; Prosmiti, Rita; Delgado-Barrio, Gerardo

2012-12-01

220

Complete pure vibrational spectrum of HD calculated without the Born-Oppenheimer approximation and including relativistic corrections  

SciTech Connect

All 18 bound pure vibrational levels of the HD molecule have been calculated within the framework that does not assume the Born-Oppenheimer (BO) approximation. The nonrelativistic energies of the states have been corrected for the relativistic effects of the order of {alpha}{sup 2} (where {alpha} is the fine structure constant), calculated using the perturbation theory with the nonrelativistic non-BO wave functions being the zero-order approximation. The calculations were performed by expanding the non-BO wave functions in terms of one-center explicitly correlated Gaussian functions multiplied by even powers of the internuclear distance and by performing extensive optimization of the Gaussian nonlinear parameters. Up to 10 000 basis functions were used for each state.

Bubin, Sergiy [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Stanke, Monika [Department of Physics, Nicholas Copernicus University, ul. Grudziadzka 5, PL-87-100 Torun (Poland); Adamowicz, Ludwik [Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States); Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States)

2011-04-15

221

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

SciTech Connect

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.}

Skokov, S. [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); Bowman, J.M. [Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322 (United States)

1998-08-01

222

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

PubMed

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

Layfield, Joshua P; Hammes-Schiffer, Sharon

2012-12-31

223

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

NASA Astrophysics Data System (ADS)

We report an investigation of the structure and vibrational modes of (AgI)x (AsSe)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 (As4Sen, 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 As4Sen 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 AsSemI3-m provided useful information augmenting the interpretation of the Raman spectra.

Kostadinova, O.; Chrissanthopoulos, A.; Petkova, T.; Petkov, P.; Yannopoulos, S. N.

2011-02-01

224

Infrared and NMR spectra, tautomerism, vibrational assignment, normal coordinate analysis, and quantum mechanical calculations of 4-amino-5-pyrimidinecarbonitrile  

NASA Astrophysics Data System (ADS)

The infrared (4000-200 cm-1) spectrum for 4-amino-5-pyrimidinecarbonitrile (APC, C5H4N4) was acquired in the solid phase. In addition, the 1H and 13C NMR spectra of APC were obtained in DMSO-d6 along with its mass spectrum. Initially, six isomers were hypothesized and then investigated by means of DFT/B3LYP and MP2(full) quantum mechanical calculations using a 6-31G(d) basis set. Moreover, the 1H and 13C NMR chemical shifts were predicted using a GIAO approximation at the 6-311+G(d,p) basis set and the B3LYP method with (and without) solvent effects using PCM method. The correlation coefficients showed good agreement between the experimental/theoretical chemical shift values of amino tautomers (1 and 2) rather than the eliminated imino tautomers (3-6), in agreement with the current quantum mechanical calculations. Structures 3-6 are less stable than the amino tautomers (1 and 2) by about 5206-8673 cm-1 (62.3-103.7 kJ/mol). The MP2(full)/6-31G(d) computational results favor the amino structure 1 with a pyramidal NH2 moiety and calculated real vibrational frequencies, however; structure 2 is considered a transition state owing to the calculated imaginary frequency. It is worth mentioning that, the calculated structural parameters suggest a strong conjugation between the amino nitrogen and pyrimidine ring. Aided by frequency calculations, normal coordinate analysis, force constants and potential energy distributions (PEDs), a complete vibrational assignment for the observed bands is proposed herein. Finally, NH2 internal rotation barriers for the stable non-planar isomer (1) were carried out using MP2(full)/6-31G(d) optimized structural parameters. Our results are discussed herein and compared to structural parameters for similar molecules whenever appropriate.

Afifi, Mahmoud S.; Farag, Rabei S.; Shaaban, Ibrahim A.; Wilson, Lee D.; Zoghaib, Wajdi M.; Mohamed, Tarek A.

225

Force-field calculation and geometry of the HOOO radical.  

PubMed

High-level ab initio calculations using the Davidson-corrected multireference configuration interaction (MRCI) level of theory with Dunning's correlation consistent basis sets and force-field calculations were performed for the HOOO radical. The harmonic vibrational frequencies and their anharmonic constants obtained by the force-field calculations reproduce the IR-UV experimental vibrational frequencies with errors less than 19 cm(-1). The rotational constants for the ground vibrational state obtained using the vibration-rotation interaction constants of the force-field calculations also reproduce the experimentally determined rotational constants with errors less than 0.9%, indicating that the present quantum chemical calculations and the derived spectroscopic constants have high accuracy. The equilibrium structure was determined from the experimentally determined rotational constants combined with the theoretically derived vibration-rotation interaction constants. The determined geometrical parameters agree well with the results of the present MRCI calculation. PMID:24028111

Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

2013-09-01

226

A split-frequency harmonic balance method for nonlinear oscillators with multi-harmonic forcing  

NASA Astrophysics Data System (ADS)

A new harmonic balance method (HBM) is presented for accurately computing the periodic responses of a nonlinear sdof oscillator with multi-harmonic forcing and non-expansible nonlinearities. The presence of multi-harmonic forcing requires a large number of solution harmonics with a substantial increase in computational demand for either the conventional or the incremental HBM. In this method, the oscillator equation-error is first defined in terms of two functions (originally proposed for obtaining free-vibration periods in: R.E. Mickens, Iteration procedure for determining approximate solutions to nonlinear oscillator equations, Journal of Sound and Vibration 116 (1987) 185 187; and more recently: R.E. Mickens, A Generalised iteration procedure for calculating approximations to periodic solutions of “truly nonlinear oscillations”, Journal of Sound and Vibration 287 (2005) 1045 1051). A Fourier series solution is assumed, in which the total number of harmonics is fixed by the chosen discrete-time interval—this series is split into two partial sums nominally associated with either low-frequency or high-frequency harmonics. By exploiting a convergence property of the equation-error functions, the total solution is obtained in a new iterative scheme in which the low-frequency components are computed via a conventional HBM using a small number of algebraic equations, whereas the high frequency components are obtained in a separate step by updating. By gradually increasing the number of harmonics in the low-frequency group, the equation-error can be progressively reduced. Efficient use is made of FFT-based algebraic equation generation which allows an important class of non-expansible nonlinearities to be handled. The proposed method is tested on a Duffing-type oscillator, and an oscillator with a non-expansible 7th power stiffness term, where in both cases up to 24 component multi-harmonic forcing is applied. As a comparison, a conventional HBM is also used on the Duffing model in which the algebraic equations are generated in symbolic form to totally avoid errors from entering the formulation through complicated expansion of the cubic stiffness term (as in: I. Senjanovi?, Harmonic analysis of nonlinear oscillations of cubic dynamical systems, Journal of Ship Research 38 (3) (1994) 225 238; and in: A. Raghothama, S. Narayanan, Periodic response and chaos in nonlinear systems with parametric excitation and time delay, Nonlinear dynamics 27 (2002) 341 365). The paper shows that in obtaining period-1 solutions, the computational accuracy and efficiency of the proposed method is very good.

Dunne, J. F.; Hayward, P.

2006-08-01

227

Design of the Active Elevon Rotor for Low Vibration.  

National Technical Information Service (NTIS)

Helicopter fuselages vibrate more than desired, and traditional solutions have limited effectiveness and can impose an appreciable weight penalty. Alternative methods of combating high vibration, including Higher Harmonic Control (HHC) via harmonic swashp...

M. V. Fulton

2000-01-01

228

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

SciTech Connect

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.

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

229

The vibrational and NMR spectra, conformations and ab initio calculations of 1-aminoethylidene propanedinitrile and its N-methyl derivatives  

NASA Astrophysics Data System (ADS)

The IR and Raman spectra of 1-aminoethylidene propanedinitrile (AE) [H2N-C(CH3)?C(CN)2], 1-(methylamino)ethylidene propanedinitrile (MAE) [CH3NH-C(CH3)?C(CN)2] and 1-(dimethylamino)ethylidene propanedinitrile (DMAE) [(CH3)2N-C(CH3)?C(CN)2] were recorded as solids and solutes in various solvents in the region 4000-50cm-1. AE and DMAE can exist only as single conformers. From the vibrational and NMR spectra of MAE in solutions, the existence of two conformers with the methyl group oriented anti and syn towards the double C?C bond were confirmed. The enthalpy difference ?H0 between the conformers was measured to be 1.9ą1.3kJmol-1 from the NMR spectra in DMSO solution. Semi-empirical (AM1, PM3, MNDO, MINDO3) and ab initio SCF calculations using a DZP basis set were carried out for all the three compounds. The calculations support the existence of two conformers anti and syn for MAE with anti being 9.4kJmol-1 more stable than syn from ab initio and 7.4, 12.0, 7.8 and 9.2kJmol-1 from AM1, PM3, MNDO and MINDO3 calculations, respectively. Finally, complete assignments of the vibrational spectra for all the three compounds were made with the aid of normal coordinate calculations employing scaled ab initio force constants. The scale factors from the similar aminomethylene propanedinitrile and its N-methyl derivatives were used and a very good agreement between calculated and experimental frequencies was achieved.

Gatial, A.; Sklenák, Š.; Milata, V.; Biskupi?, S.; Salzer, R.; Scheller, D.; Woelki, G.

1999-10-01

230

LETTER TO THE EDITOR: Ab initio calculation of the local vibrational modes of the interstitial boron interstitial oxygen defect in Si  

NASA Astrophysics Data System (ADS)

The first stage in the anneal of interstitial boron below room temperature in Czochralski-grown Si (Cz-Si) is the formation of the interstitial boron-oxygen (BiOi) defect. First principles modelling show that this defect has a structure similar to the interstitial carbon-oxygen complex. However, whereas the latter defect has been characterized by local vibrational mode infra-red spectroscopy, there is no information on the local vibrational modes of BiOi even though the defect is known to be a dominant interstitial boron defect in irradiated Cz-Si. Here, we carry out density functional calculations to determine its vibrational modes and respective isotope shifts, concluding that it possesses six local vibrational modes. As in the case of CiOi, we find an oxygen-related vibrational mode with frequency far below the 1136 cm-1 of the oxygen interstitial, characteristic of the three-fold coordinated oxygen.

Carvalho, A.; Jones, R.; Coutinho, J.; Briddon, P. R.

2005-05-01

231

Ab initio calculation of vibrational spectra of orthorhombic IV-VI layered crystals  

NASA Astrophysics Data System (ADS)

Phonon modes of IV-VI semiconductor crystals with the orthorhombic structure of the crystal lattice have been calculated from first principles using the linear response method. The calculations are compared with the results of theoretical calculations available in the literature for some of the crystals and with the experimental data obtained by IR and Raman spectroscopies. Equilibrium lattice parameters and phonon spectra are calculated for all the crystals.

Gashimzade, F. M.; Guseinova, D. A.; Jahangirli, Z. A.; Nizametdinova, M. A.

2013-09-01

232

Hydrogen-bonded phenol-acid clusters studied by vibrational resolved laser spectroscopy and ab initio calculations. I. Formic acid  

NASA Astrophysics Data System (ADS)

The hydrogen-bonded complexes of phenol with one and two molecules of formic acid are studied by resonant two-photon ionization, IR-UV double-resonance spectroscopy, dispersed fluorescence spectroscopy and ab initio calculations at the Hartree-Fock level. The shifts of the electronic spectra, the intermolecular vibrations in the S 0 and S 1 states and the calculated binding energies point to cyclic arrangements for both phenol(formic acid) 1 and phenol(formic acid) 2. Phenol is involved in two hydrogen bonds acting as proton donor to the carboxylic group of the acid and as proton acceptor. The stable (formic acid) 2 dimer opens to allow insertion of a phenol molecule and formation of a cyclic phenol(formic acid) 2 structure.

Imhof, Petra; Roth, Wolfgang; Janzen, Christoph; Spangenberg, Daniel; Kleinermanns, Karl

1999-04-01

233

Composed vibration pulses for ultrasound vibrometry  

Microsoft Academic Search

Composed vibration pulses are developed to generate ultrasound radiation force for stimulating vibrations in a tissue region with preferred spectral distributions and increasing specific vibration harmonics when the peak radiation power is limited. The new vibration sequence has multiple pulses in one fundamental period of the vibration. The pulses are sparsely sampled from an orthogonal frequency wave composed of several

Yi Zheng; Aiping Yao; Yu Liu; Ke Chen; Shigao Chen; Matthew W. Urban; James F. Greenleaf

2010-01-01

234

Global Calculations Using Potential Functions and Effective Hamiltonian Models for Vibration-Rotation Spectroscopy and Dynamics of Small Polyatomic Molecules  

NASA Astrophysics Data System (ADS)

It has become increasingly common to use accurate potential energy surfaces and dipole moment surfaces for predictions and assignment of high-resolution vibration-rotation molecular spectra. These surfaces are obtained either from high-level ab initio electronic structure calculations or from a direct fit to experimental spectroscopic data. The talk will continue a discussion of some recent advances in the domain of the "potentiology". The role of basis extrapolations, of the Born-Oppenheimer breakdown corrections , in particular for very highly excited vibration states will be considered. As effective polyad Hamiltonians and band transition moment operators are still widely used for data reductions in high-resolutions molecular spectroscopy, experimental spectra analyses invoke a need for accurate methods of building physically meaningful effective models from ab initio surfaces. This involves predictions for various spectroscopic constants, including vibration dependence of rotational and centrifugal distortion and resonance coupling parameters. Topics planned for discussion include: high-order Contact Transformations of rovibrational Hamiltonians and of the dipole moment for small polyatomic molecules; convergence issues; the role of the anharmonicity in a potential energy function and of resonance couplings on the normal mode mixing and on vib-rot assignments with application to high energy vibration levels of SO_2 and to ozone near the dissociation limit; intensity anomalies in H_2S / HDS / D_2S spectra, relation of the shape of ab initio dipole moment surfaces with a "mystery" of nearly vanishing symmetry allowed bands. A full account for symmetry properties requires efficient theoretical tools for transformations of molecular Hamiltonians such as irreducible tensor formalism, applications using phosphine and methane potentials will be discussed. Both potential functions and effective polyad Hamiltonians allow studying changes in quasi-classical vibration periodic orbits and in of the nodal structure of wavefunctions with mass variations. An investigation of the consequences of symmetry breaking by isotopic substitution, in the classical and quantum dynamics is particularly instructive. This helps understanding the fingerprints of bifurcations effects in the quantum states of isotopologues and their assignment. The work of our research team with collaborators in these areas will be described.

Tuyterev, Vladimir

2010-06-01

235

Simulations of solid-state vibrational circular dichroism spectroscopy of (S)-alternarlactam by using fragmentation quantum chemical calculations.  

PubMed

Simulations of vibrational circular dichroism (VCD) spectroscopy of optical active aggregates of chiral molecules in the amorphous solid encounter great difficulties in the description of complicated intermolecular interactions by using the conventional quantum mechanical (QM) methods. The fragmentation approach is applied to calculate the VCD spectra of the covalently bonded oligomers and nonbonded molecular aggregates of (S)-alternarlactam, a new fungal cytotoxin with cyclopentenone and isoquinolinone scaffolds. Starting from the statistically averaged configurations that are sampled from the molecular dynamic simulations, the target oligomers or packing systems are divided into several fragments with a proper treatment of boundary effects on the separated segments. Each fragment is embedded in the background point charges centered on the distant atoms to simulate the long-range electrostatic interactions. The total VCD signals are assembled from the rotational strength of all the fragments. Test calculations on the ?-bonded oligomers and molecular aggregates using fragmentation method show good agreement with the conventional QM results. The packing effects on the infrared (IR) absorption and VCD spectroscopies of amorphous (S)-alternarlactam solid are investigated with density of 0.5 and 0.8 g/cm(3), respectively. The fragment-based VCD calculations on (S)-alternarlactam aggregates give a better agreement with experimental spectra than the Boltmann-weighted spectra of various possible monomeric, dimeric, and trimeric configurations. Hydrogen-bonded networks are the dominant packing configurations at the density of 0.5 g/cm(3). The (C?)OˇˇˇH-N hydrogen-bonding interactions result in the signal splitting of IR and VCD spectra at the C?O stretching vibrational regions. When the density is increased to 0.8 g/cm(3), ?-? stacking turns to be the dominating intermolecular interaction pattern. The computational cost of fragmentation calculation scales linearly with the number of the molecular fragments, facilitating the future applications to a wide range of the large-sized chiral systems. PMID:21391541

Jiang, Nan; Tan, Ren Xiang; Ma, Jing

2011-03-10

236

Interaction of atomic hydrogen with a UV pulse: model based calculations of the energy transfers from the laser field into both the electron kinetic energy and the harmonics  

NASA Astrophysics Data System (ADS)

We study both the above-threshold ionization spectrum and harmonics generation resulting from the interaction of atomic hydrogen with a UV pulse. Our calculations are based on the solution of the time-dependent Schrödinger equation in momentum space where the kernel of the non-local Coulomb potential is replaced by a sum of separable potentials, each of them supporting one bound state of atomic hydrogen. It is shown that the interaction of hydrogen with a field, the frequency of which corresponds to the 1s-2p transition, leads, quite unexpectedly, to the emission of very energetic electrons.

Tetchou Nganso, H. M.; Popov, Yu V.; Piraux, B.; Madrońero, J.; Njock, M. G. Kwato

2012-11-01

237

On determination of the natural frequency of transverse and longitudinal vibrations of a cracked beam. Part 2. Experimental and calculation results  

Microsoft Academic Search

The results of experimental investigation of the relationship between the natural frequency of the first mode bending and\\u000a longitudinal vibrations of titanium alloy and alloyed steel cantilever beams and the crack parameters (crack depth and location)\\u000a are presented together with the data on calculation of the relative change of the vibration frequency of cracked beams, which\\u000a are obtained by the

A. P. Bovsunovskii

1999-01-01

238

A theoretical approach to the molecular structure and vibrational spectrum of the AlC{sub 2}H{sub 4} complex from CASSCF and UHF second-order perturbation calculations  

SciTech Connect

Ab initio quantum mechanical calculations have been carried out on the molecular structure and vibrational spectra of the AlC{sub 2}H{sub 4} complex. Equilibrium geometries, harmonic force fields, and frequencies have been calculated by using a double-{zeta} basis set with polarization functions on the heavy atoms at CASSCF and UHF second-order Moller-Plesset levels. The preferred type of the aluminum-ethylene bonding, {pi}-bonded (C{sub 2v}) or {sigma}-bonded (C{sub s}), depends dramatically on the wave function being correlated or not, and the author`s calculations show that the effect of the electron correlation is of nondynamical character. The low value found for the force constant F{sub Al-C} reveals the weakness of the Al-C bond while the lowering of the force constant associated with C-C stretching shows that the ethylenic C-C bond is considerably weakened upon complexation. The calculated frequencies both for AlC{sub 2}H{sub 4} and its isotopic derivatives agree reasonably well with the experiment. 22 refs., 1 fig., 7 tabs.

Sanz, J.F.; Marquez, A.; Anguiano, J. [Univ. of Sevilla (Spain)

1992-08-20

239

Vibrational properties of hexagonal boron nitride: inelastic X-ray scattering and ab initio calculations.  

PubMed

The phonon dispersion relations of bulk hexagonal boron nitride have been determined from inelastic x-ray scattering measurements and analyzed by ab initio calculations. Experimental data and calculations show an outstanding agreement and reconcile the controversies raised by recent experimental data obtained by electron-energy loss spectroscopy and second-order Raman scattering. PMID:17359168

Serrano, J; Bosak, A; Arenal, R; Krisch, M; Watanabe, K; Taniguchi, T; Kanda, H; Rubio, A; Wirtz, L

2007-03-01

240

Polarizability calculation of vibrating nanoparticles for intensity of low wavenumber Raman scattering  

Microsoft Academic Search

A new numerical method is introduced for calculating the polarizability of an arbitrary dielectric object with position dependent complex permittivity. Three separate numerical approaches are provided to calculate the dipole moment of a nanoparticle embedded in a dielectric matrix in the presence of an applied electric field. Numerical tests confirm the accuracy of this method when applied to several cases

Daniel B. Murray; Caleb H. Netting; Robin D. Mercer; Lucien Saviot

2007-01-01

241

Three-Dimensional Quantum Calculations on the Ground and Excited State Vibrations of Ethylene.  

National Technical Information Service (NTIS)

Three dimensional potential energy surfaces of the ground and excited states of ethylene were calculated at the MRCEPA (Multi Reference Coupled Electronic Pair Approximation) level. The modes included are the torsion, the CC stretch, and the symmetric sci...

G. C. Groenenboom

1991-01-01

242

Polarizability calculation of vibrating nanoparticles for intensity of low wavenumber Raman scattering  

Microsoft Academic Search

A new numerical method is introduced for calculating the polarizability of an\\u000aarbitrary dielectric object with position dependent complex permittivity. Three\\u000aseparate numerical approaches are provided to calculate the dipole moment of a\\u000ananoparticle embedded in a dielectric matrix in the presence of an applied\\u000aelectric field. Numerical tests confirm the accuracy of this method when\\u000aapplied to several cases

Daniel B. Murray; Caleb H. Netting; Robin D. Mercer; Lucien Saviot

2007-01-01

243

Structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide) SF5N=S(O)F2: vibrational analysis, gas electron diffraction, and quantum chemical calculations.  

PubMed

The molecular structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide), SF5N=S(O)F2, have been studied by vibrational spectroscopy (IR (gas) and Raman (liquid)), by gas electron diffraction (GED), and by quantum chemical calculations (MP2 and B3LYP with (6-31G(d) and 6-311+G(2df) basis sets). According to GED, the prevailing conformer possesses a syn structure (N-SF5 bond synperiplanar with respect to the bisector of the SF2 group). Splitting of the symmetric N=S=O stretching vibration in gas and liquid spectra demonstrates the presence of a second conformer (11(5)%) with anticlinal orientation of the N-SF5 bond according to quantum chemical calculations. The geometric structure, conformational properties, and vibrational frequencies are well reproduced by quantum chemical calculations. PMID:17388270

Alvarez, Rosa M S; Cutin, Edgardo H; Mews, Rüdiger; Oberhammer, Heinz

2007-02-23

244

FTIR and FT-Raman spectra, vibrational assignments and density functional theory calculations of 2,6-dibromo-4-nitroaniline and 2-(methylthio)aniline  

NASA Astrophysics Data System (ADS)

The FTIR and FT-Raman spectra of 2,6-dibromo-4-nitroaniline (2,6-DB4NA) in solid phase and 2-(methylthio)aniline (2-MTA) in liquid phase were measured. The geometry and normal vibrations have been obtained from the density functional theory (DFT) with the B3LYP method employing the 6-31G* basis set. Scale factors, which bring computational frequencies in closer agreement with the experimental data, have been calculated for predominant vibrational motions of the normal modes. The effects of the amino, bromine, nitro, thio and methyl substituents on vibrational frequencies have been investigated. The infrared and Raman spectra were also predicted from the calculated intensities. The observed and the calculated spectra were found to be in good agreement.

Krishnakumar, V.; Balachandran, V.

2005-06-01

245

Vibrational thermodynamics of materials  

Microsoft Academic Search

The literature on vibrational thermodynamics of materials is reviewed. The emphasis is on metals and alloys, especially on the progress over the last decade in understanding differences in the vibrational entropy of different alloy phases and phase transformations. Some results on carbides, nitrides, oxides, hydrides and lithium-storage materials are also covered.Principles of harmonic phonons in alloys are organized into thermodynamic

Brent Fultz

2010-01-01

246

Calculation of cross sections for vibrational excitation and dissociative attachment in electron collisions with HBr and DBr  

SciTech Connect

The nonlocal resonance model developed earlier for the description of low-energy inelastic and reactive electron-HCl collisions has been adapted to the electron-HBr collision system. The parameters of the model have been determined by fitting the eigenphase sum in the fixed-nuclei approximation to the data of an {ital ab} {ital initio} {ital R}-matrix calculation of Morgan, Burke, and collaborators. The Schwinger-Lanczos method has been employed to solve the nuclear scattering problem with a nonlocal, complex, and energy-dependent effective potential. Fully converged cross sections have been obtained on a dense grid of energies for many vibrational excitation, deexcitation, and dissociative channels in both HBr and DBr. The computed cross sections are generally in good agreement with experiment as far as data are available. {copyright} {ital 1996 The American Physical Society.}

Horacek, J. [Department of Theoretical Physics (Czech Republic)]|[Faculty of Mathematics and Physics, Charles University Prague]|[V Holesovickach 2, 180 00 Praha 8]|[Czech Republic; Domcke, W. [Institute of Physical and Theoretical Chemistry]|[Technical University Munich]|[D-85748 Garching (Germany)

1996-04-01

247

The isomers and conformers of some push pull enamines studied by vibrational and NMR spectroscopy and by ab initio calculations  

NASA Astrophysics Data System (ADS)

The isomers and conformers of six push pull enamines: 3-dimethylamino-, 3-methylamino- and 3-amino-2-acetyl propenenitrile [(H3C)2N CHC(CN)(COCH3), H3C NH CHC(CN)(COCH3) and H2N CHC(CN)(COCH3)] and 3-dimethylamino-, 3-methylamino- and 3-amino-2-methylsulfonyl propenenitrile [(H3C)2N CHC(CN)(SO2CH3), H3C NH CHC(CN)(SO2CH3) and H2N CHC(CN)(SO2CH3)] have been studied experimentally by vibrational and NMR spectroscopy and theoretically by the ab initio calculations at MP2 level in 6-31G** basis set. The IR and Raman spectra of all compounds as a solid and solute in various solvents have been recorded in the region 4000 50 cm-1. The NMR spectra were obtained in chloroform and DMSO at room temperature. All six compounds have been prepared by the same way. NMR spectra revealed that both dimethylamino compounds were prepared as a pure E isomers whereas in the case of methylamino compounds the 3-methylamino-2-methylsulfonyl propenenitrile was prepared also as a pure E isomer but 3-methylamino-2-acetyl propenenitrile as a pure Z isomer. Also 3-amino-2-methylsulfonyl propenenitrile was obtained as a pure the E isomer, but 3-amino-2-acetyl propenenitrile as a mixture of both E and Z isomers. Confomational possibilities of studied compounds are given only by the rotation of the acetyl and methylamino groups. Vibrational spectra revealed existence of two conformers with Z and E orientation of acetyl group for 3-dimethylamino-2-acetyl propenenitrile. Two conformers with anti or syn orientation of methylamino group for 3-methylamino-2-methylsulfonyl propenenitrile have been confirmed by vibrational and NMR spectra, but only one conformer with anti orientation of methylamino group for 3-methylamino-2-acetyl propenenitrile in chloroform solution and in solid phase was found. For latter compound the additional isomer/conformer was detected in more polar solvents (acetonitrile/DMSO). These experimental findings have been supported by ab initio solvent effect calculations.

Pigošová, J.; Gatial, A.; Milata, V.; ?ernuchová, P.; Prónayová, N.; Liptaj, T.; Mat?jka, P.

2005-06-01

248

Analysis of Vibrational Spectra of Pyridoxazinone Based on Density Functional Theory Calculations  

NASA Astrophysics Data System (ADS)

Solid phase FTIR and FT-Raman spectra of pyridoxazinone have been recorded in regions of 4000-50 cm-1 and 3500-100 cm-1 respectively. The spectra were interpreted by normal coordinate analysis following full structure optimizations and force field calculations based on density functional theory (DFT) using the standard B3LYP/6-31G* and B3LYP/6-311+G** method and basis set combinations. The results of the calculations are applied to simulate infrared and Raman spectra of the title compound, which showed excellent agreement with the observed spectra.

Ramasamy, R.

2013-09-01

249

Identification of hydrogen defects in SrTiO3 by first principles local vibrational mode calculations  

SciTech Connect

For over three decades, the infrared spectroscopy peaks of around 3500 cm{sup -1} observed in hydrogen-doped SrTiO{sub 3} samples have been assigned to an interstitial hydrogen (H{sub i}) attached to a lattice oxygen with two possible configuration models: the octahedral edge (OE) and the cubic face (CF) models. Based on our first-principles calculations of H{sub i} around O, both OE and CF configurations are not energetically stable. Starting from either configuration, the H{sub i} would spontaneously relax into an off axis (OA) site; lowering the energy by 0.25 eV or more. The calculated vibrational frequency of 2745 cm{sup -1} for OA invalidates the assignment of H{sub i} to the observed 3500 cm{sup -1} peak. In addition, the calculated diffusion barrier is low, suggesting that H{sub i} can be easily annealed out. We propose that the observed peaks around 3500 cm{sup -1} are associated with defect complexes. A Sr vacancy (V{sub Sr}) can trap H{sub i} and form a H-V{sub Sr} complex which is both stable and has the frequency in agreement with the observed main peak. The complex can also trap another H{sub i} and form 2H-V{sub Sr}; consistent with the observed additional peaks at slightly higher frequencies (3510-3530 cm{sup -1}).

T-Thienprasert, J [Kasetsart University, Thailand; Fongkaew, Ittipon [Suranaree University; Singh, David J [ORNL; Du, Mao-Hua [ORNL; Limpijumnong, Sukit [Kasetsart University, Thailand

2012-01-01

250

Vibrational frequencies for NO chemisorbed on different sites: DFT calculations on Pd clusters  

Microsoft Academic Search

Density functional theory calculations within the adiabatic coupling method have been performed for NO bound to Pd clusters exhibiting the structure appropriate to Pd{110} in order to estimate the influence of adsorption site on the NO stretching frequency. Three cluster sizes were investigated, with four, five and eight Pd atoms. In each case the N?O bond length is found to

Manuel Pérez Jigato; Kausala Somasundram; Volker Termath; Nicholas C. Handy; David A. King

1997-01-01

251

An ab initio calculation of the fundamental and overtone HCl stretching vibrations for the HCl dimer  

Microsoft Academic Search

We have previously determined an analytical ab initio six-dimensional potential energy surface for the HCl dimer, and have used it to determine the minimum energy path for the trans-tunneling motion. In the present paper we refine this path by fitting to data. We calculate a further 178 ab initio points in order to determine the HCl stretching energies, and HCl

Per Jensen; P. R. Bunker; V. C. Epa; A. Karpfen

1992-01-01

252

Microwave, infrared and Raman spectra, r0 structural parameters, ab initio calculations and vibrational assignment of 1-fluoro-1-silacyclopentane.  

PubMed

The microwave spectrum (6500-18 ,500 MHz) of 1-fluoro-1-silacyclopentane, c-C(4)H(8)SiHF has been recorded and 87 transitions for the (28)Si, (29)Si, (30)Si, and (13)C isotopomers have been assigned for a single conformer. Infrared spectra (3050-350 cm(-1)) of the gas and solid and Raman spectrum (3100-40 cm(-1)) of the liquid have also been recorded. The vibrational data indicate the presence of a single conformer with no symmetry which is consistent with the twist form. Ab initio calculations with a variety of basis sets up to MP2(full)/aug-cc-pVTZ predict the envelope-axial and envelope-equatorial conformers to be saddle points with nearly the same energies but much lower energy than the planar conformer. By utilizing the microwave rotational constants for seven isotopomers ((28)Si, (29)Si, (30)Si, and four (13)C) combined with the structural parameters predicted from the MP2(full)/6-311+G(d,p) calculations, adjusted r(0) structural parameters have been obtained for the twist conformer. The heavy atom distances in A? are: r(0)(SiC(2)) = 1.875(3); r(0)(SiC(3)) = 1.872(3); r(0)(C(2)C(4)) = 1.549(3); r(0)(C(3)C(5)) = 1.547(3); r(0)(C(4)C(5)) = 1.542(3); r(0)(SiF) = 1.598(3) and the angles in degrees are: [angle]CSiC = 96.7(5); [angle]SiC(2)C(4) = 103.6(5); [angle]SiC(3)C(5) = 102.9(5); [angle]C(2)C(4)C(5) = 108.4(5); [angle]C(3)C(5)C(4) = 108.1(5); [angle]F(6)Si(1)C(2) = 110.7(5); [angle]F(6)Si(1)C(3) = 111.6(5). The heavy atom ring parameters are compared to the corresponding r(s) parameters. Normal coordinate calculations with scaled force constants from MP2(full)/6-31G(d) calculations were carried out to predict the fundamental vibrational frequencies, infrared intensities, Raman activities, depolarization values, and infrared band contours. These experimental and theoretical results are compared to the corresponding quantities of some other five-membered rings. PMID:22299870

Durig, James R; Panikar, Savitha S; Obenchain, Daniel A; Bills, Brandon J; Lohan, Patrick M; Peebles, Rebecca A; Peebles, Sean A; Groner, Peter; Guirgis, Gamil A; Johnston, Michael D

2012-01-28

253

Microwave, infrared and Raman spectra, r0 structural parameters, ab initio calculations and vibrational assignment of 1-fluoro-1-silacyclopentane  

NASA Astrophysics Data System (ADS)

The microwave spectrum (6500-18 500 MHz) of 1-fluoro-1-silacyclopentane, c-C4H8SiHF has been recorded and 87 transitions for the 28Si, 29Si, 30Si, and 13C isotopomers have been assigned for a single conformer. Infrared spectra (3050-350 cm-1) of the gas and solid and Raman spectrum (3100-40 cm-1) of the liquid have also been recorded. The vibrational data indicate the presence of a single conformer with no symmetry which is consistent with the twist form. Ab initio calculations with a variety of basis sets up to MP2(full)/aug-cc-pVTZ predict the envelope-axial and envelope-equatorial conformers to be saddle points with nearly the same energies but much lower energy than the planar conformer. By utilizing the microwave rotational constants for seven isotopomers (28Si, 29Si, 30Si, and four 13C) combined with the structural parameters predicted from the MP2(full)/6-311+G(d,p) calculations, adjusted r0 structural parameters have been obtained for the twist conformer. The heavy atom distances in A? are: r0(SiC2) = 1.875(3); r0(SiC3) = 1.872(3); r0(C2C4) = 1.549(3); r0(C3C5) = 1.547(3); r0(C4C5) = 1.542(3); r0(SiF) = 1.598(3) and the angles in degrees are: ?CSiC = 96.7(5); ?SiC2C4 = 103.6(5); ?SiC3C5 = 102.9(5); ?C2C4C5 = 108.4(5); ?C3C5C4 = 108.1(5); ?F6Si1C2 = 110.7(5); ?F6Si1C3 = 111.6(5). The heavy atom ring parameters are compared to the corresponding rs parameters. Normal coordinate calculations with scaled force constants from MP2(full)/6-31G(d) calculations were carried out to predict the fundamental vibrational frequencies, infrared intensities, Raman activities, depolarization values, and infrared band contours. These experimental and theoretical results are compared to the corresponding quantities of some other five-membered rings.

Durig, James R.; Panikar, Savitha S.; Obenchain, Daniel A.; Bills, Brandon J.; Lohan, Patrick M.; Peebles, Rebecca A.; Peebles, Sean A.; Groner, Peter; Guirgis, Gamil A.; Johnston, Michael D.

2012-01-01

254

Characteristics of atomic vibrational motion in a one-component defective crystal  

NASA Astrophysics Data System (ADS)

Vibrations of atoms in a defective argon crystal are considered. Frequencies are calculated in the harmonic approximation and Mie and Einstein approximations. The vibrations are calculated for a set of local clusters differing in the position of a vacancy at different distances from a selected atom. Probabilities for these clusters are calculated within a quasichemical approximation of the lattice gas model. It is shown that when combined contributions from lateral interactions and vibrational motions are allowed for in the free crystal energy, there is an increase in the lattice constant upon a rise in temperature in all approximations. It is found that the frequencies calculated using the Mie model become closer to the frequency distribution in the harmonic approximation as the degree of crystal defectiveness increases.

Tovbin, Yu. K.; Titov, S. V.

2013-10-01

255

Post-processing of EPR spectra by convolution filtering: calculation of a harmonics' series and automatic separation of fast-motion components from spin-label EPR spectra.  

PubMed

This communication reports on post-processing of continuous wave EPR spectra by a digital convolution with filter functions that are subjected to differentiation or the Kramers-Krönig transform analytically. In case of differentiation, such a procedure improves spectral resolution in the higher harmonics enhancing the relative amplitude of sharp spectral features over the broad lines. At the same time high-frequency noise is suppressed through filtering. These features are illustrated on an example of a Lorentzian filter function that has a principal advantage of adding a known magnitude of homogeneous broadening to the spectral shapes. Such spectral distortion could be easily and accurately accounted for in the consequent least-squares data modeling. Application examples include calculation of higher harmonics from pure absorption echo-detected EPR spectra and resolving small hyperfine coupling that are unnoticeable in conventional first derivative EPR spectra. Another example involves speedy and automatic separation of fast and broad slow-motion components from spin-label EPR spectra without explicit simulation of the slow motion spectrum. The method is illustrated on examples of X-band EPR spectra of partially aggregated membrane peptides. PMID:17967556

Smirnov, Alex I

2007-10-14

256

Density functional theory study, FT-IR and FT-Raman spectra and SQM force field calculation for vibrational analysis of 1, 3-Bis (hydroxymethyl) benzimidazolin-2-one  

NASA Astrophysics Data System (ADS)

FT-IR and FT-Raman spectra of 1, 3-Bis (hydroxymethyl) benzimidazolin-2-one were recorded and analyzed in the solid phase. The optimized molecular geometry and vibrational wavenumbers have also been calculated in optimized structure by using DFT method. Scaled quantum mechanical force fields have also been used to calculate potential energy distributions in order to make conspicuous vibrational assignments. The red shifting of the Osbnd H stretching wavenumber is due to the formation of Osbnd H⋯O intermolecular hydrogen bonding. The lowering and splitting of the carbonyl stretching vibrational modes is assigned to the intermolecular association based on Cdbnd O⋯H type hydrogen bonding in the molecule. Chemical interpretation of hyperconjugative interactions was done by natural bond orbital analysis.

Joseph, Lynnette; Sajan, D.; Chaitanya, K.; Devarajegowda, H. C.; Isac, Jayakumary

2013-10-01

257

Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations.  

PubMed

Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from the heartwood of Auxemma oncocalyx Taub popularly known as "pau branco". Oncocalyxone A (Onco A) has many pharmaceutical uses such as: antitumor, analgesic, antioxidant and causative of inhibition of platelet activation. We have performed the optimized geometry, total energy, conformational study, molecular electrostatic potential mapping, frontier orbital energy gap and vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set. Stability of the molecule arising from hyperconjugative interactions and/or charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was recorded in DMSO and MeOH solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using IEF-PCM and 6-31G basis set. The (13)C NMR chemical shifts have been calculated with the B3LYP/6-311++G(d,p) basis set and compared with the experimental values. These methods have been used as tools for structural characterization of Onco A. PMID:23747376

Joshi, Bhawani Datt; Srivastava, Anubha; Honorato, Sara Braga; Tandon, Poonam; Pessoa, Otília Deusdęnia Loiola; Fechine, Pierre Basílio Almeida; Ayala, Alejandro Pedro

2013-05-20

258

Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations  

NASA Astrophysics Data System (ADS)

Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from the heartwood of Auxemma oncocalyx Taub popularly known as "pau branco". Oncocalyxone A (Onco A) has many pharmaceutical uses such as: antitumor, analgesic, antioxidant and causative of inhibition of platelet activation. We have performed the optimized geometry, total energy, conformational study, molecular electrostatic potential mapping, frontier orbital energy gap and vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d, p) basis set. Stability of the molecule arising from hyperconjugative interactions and/or charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was recorded in DMSO and MeOH solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using IEF-PCM and 6-31G basis set. The 13C NMR chemical shifts have been calculated with the B3LYP/6-311++G(d, p) basis set and compared with the experimental values. These methods have been used as tools for structural characterization of Onco A.

Joshi, Bhawani Datt; Srivastava, Anubha; Honorato, Sara Braga; Tandon, Poonam; Pessoa, Otília Deusdęnia Loiola; Fechine, Pierre Basílio Almeida; Ayala, Alejandro Pedro

2013-09-01

259

Analysis of a System of Two Weakly Non-Linear Coupled Harmonic Oscillators Arising from the Field of Wind-Induced Vibrations.  

National Technical Information Service (NTIS)

In the paper a system of two weakly non-linear coupled harmonic oscillators is considered. For the lower order frequency ratios the influence of the coupling terms on the occurrence and (local) stability of periodic motions is studied, as well as the glob...

C. G. A. van der Beek

1989-01-01

260

Determination of Ground State Vibrational Frequencies of Jet-Cooled Resorcinol by Means of Dispersed Fluorescence Spectroscopy and ab Initio Calculations  

NASA Astrophysics Data System (ADS)

The vibrational frequencies of the electronic ground state of resorcinol have been determined via laser-induced dispersed fluorescence spectroscopy. An assignment based on comparison with ab initio calculations on the MP2 and B3LYP (6-311 G (d,p)) level is presented.

Imhof, Petra; Brause, Robert; Kleinermanns, Karl

2002-01-01

261

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)

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.

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

1992-06-01

262

Flexual Rigidity of a Thin Walled Build-Up Rotor for Jet Engine. Measurement by Static Load Test and Vibration Test and Calculation by Finite Element Method.  

National Technical Information Service (NTIS)

Results of flexural rigidity tests and flexural vibration tests of a thin walled built-up rotor for a single spool jet engine are presented. Calculations of deformation of the rotor under similar loading and supporting conditions occuring in the tests are...

T. Miyachi A. Ogawa S. Hoshiya Y. Sofue

1973-01-01

263

Monte Carlo direct (test-particle) simulation of rotational and vibrational relaxation and dissociation of diatomic molecules using classical trajectory calculations  

NASA Astrophysics Data System (ADS)

For the physically accurate simulation of molecular gases, the CTC-DSMC method is developed by directly coupling classical trajectory calculations (CTC) for rigid and vibrating rotators with the direct simulation Monte Carlo (DSMC) method. Using the CTC-DSMC method for rigid rotators, the rotational relaxation of nitrogen through a normal shock wave is simulated by employing the accurate potential energy surface. The CTC-DSMC results agree well with the experimental results. The CTC-DSMC method for vibrating rotators is used for the simulation of the vibrational relaxation and dissociation of oxygen infinitely dilute in an isothermal heat bath of argon with the model potentials, where the test-particle procedure is efficiently employed. It is shown that the dissociation occurs preferentially from the upper rotational quantum levels over almost all the vibrational quantum levels and that the steady velocity, rotational, and vibrational distributions considerably deviate from the heat-bath equilibrium distributions. The CTC-DSMC calculation reasonably reproduces the experimental results measured in shock-heated dilute oxygen-argon mixtures. .

Koura, Katsuhisa

2001-08-01

264

Ab Initio Calculation Of Vibrational Frequencies In AsxS1-x Glass And The Raman Spectra  

NASA Astrophysics Data System (ADS)

We have made many different models for the understanding of the structure of AsS glass. In particular, we made the models of AsS3 (triangular), AsS3 (pyramid), AsS4 (3S on one side, one on the other side of As, S3-As-S), AsS4 (pyramid), AsS4 (tetrahedral), AsS7, As2S6 (dumb bell), As2S3 (bipyramid), As2S3 (zig-zag), As3S2 (bipyramid), As3S2 (linear), As4S4 (cubic), As4S4 (ring), As4S (tetrahedral), As4S (pyramid), As4S3 (linear) and As6S2 (dumb bell) by using the density functional theory which solves the Schrödinger equation for the given number of atoms in a cluster in the local density approximation. The models are optimized for the minimum energy which determines the structures, bond lengths and angles. For the optimized clusters, we calculated the vibrational frequencies in each case by calculating the gradients of the first principles potential. We compare the experimentally observed Raman frequencies with those calculated so that we can identify whether the cluster is present in the glass. In this way we find that AsS4 (S3-As-S), As4S4 (ring), As2S3 (bipyramid), As4S4 (cubic), As4S3 (linear), As2S3 (zig-zag), AsS4 (Td), As2S6 (dumb bell), AsS3 (triangle) and AsS3 (pyramid) structures are present in the actual glass.

Rosli, Ahmad Nazrul; Kassim, Hasan Abu; Shrivastava, Keshav N.

2009-06-01

265

Isomers and conformers of two push pull hydrazines studied by NMR and vibrational spectroscopy and by ab initio calculations  

NASA Astrophysics Data System (ADS)

The isomers and conformers of two push pull hydrazines: 3-N,N-dimethylhydrazino-2-acetyl propenenitrile [(H3C)2NNHCHC(CN)(COCH3)] (DMHAP) and 3-N,N-dimethylhydrazino-2-methylsulfonyl propenenitrile [(H3C)2NNHCHC(CN)(SO2CH3)] (DMHSP) have been studied experimentally by NMR and vibrational spectroscopy and theoretically by the ab initio calculations at MP2 level in 6-31G** basis set. The IR and Raman spectra of both compounds as a solid and solute in various solvents have been recorded. The NMR spectra were obtained in chloroform and DMSO at room temperature. Both compounds have been prepared by the same way. NMR spectra revealed that DMHAP was prepared as a pure Z-isomer whereas in the case of DMHSP a pure E-isomer was obtained. Due to the low barrier for both compounds practically free isomerisation process occurred in the solutions but in opposite directions. Whereas DMHAP exists in the solid state and in the less polar solvent as Z-isomer, in more polar solvents the appearance of next two conformers of E-isomer was observed. On the contrary DMHSP exists in the solid state and in the more polar solvent as E-isomer only but in less polar solvent the presence of Z-isomer was observed as well. Conformational possibilities of both studied compounds are given by the rotation of dimethylhydrazino group with its anti- or syn-orientation towards the olefinic double bond. Moreover, by the rotation of the acetyl group with Z- and E-orientation of carbonyl bond towards olefinic double bond can occur in DMHAP. Vibrational and NMR spectra revealed the existence of single conformer with intramolecular hydrogen bond for Z-isomer in less polar solvent and next two conformers for E-isomer of DMHAP with Z-orientation of acetyl group and anti and syn orientation of dimethylhydrazine group in more polar solvents. For E-isomer of DMHSP two conformers with anti or syn orientations of dimethylhydrazino group have been also confirmed by NMR spectra in more polar solvents. Additionally the third DMHSP conformer with anti orientation of dimethylhydrazino group originating from Z-isomer was detected in less polar solvents. These experimental findings have been supported by ab initio calculations with solvent effect inclusion.

Gróf, M.; Polovková, J.; Gatial, A.; Milata, V.; ?ernuchová, P.; Prónayová, N.; Mat?jka, P.

2007-05-01

266

Prediction and measurements of vibrations from a railway track lying on a peaty ground  

Microsoft Academic Search

This paper introduces a two-dimensional model for the response of the ground surface due to vibrations generated by a railway traffic. A semi-analytical wave propagation model is introduced which is subjected to a set of harmonic moving loads and based on a calculation method of the dynamic stiffness matrix of the ground. In order to model a complete railway system,

B. Picoux; R. Rotinat; J. P. Regoin; D. Le Houédec

2003-01-01

267

Travelling Wave Ultrasonic Motors, Part II: A Numerical Method For The Flexural Vibrations Of The Stator  

Microsoft Academic Search

A finite difference scheme is used to calculate the forced transverse vibrations of thin annular plates with radially varying thickness. Under the assumption of harmonic motion, the governing partial differential equation reduces to a system of ordinary differential equations with variable coefficients. The numerical scheme that solves this system for various boundary conditions is successfully tested vs. known analytical solutions,

P. Hagedorn; J. Wallaschek; W. Konrad

1993-01-01

268

Vibrational spectroscopy of polyatomic materials: Semiempirical calculations of anharmonic couplings and infrared and Raman linewidths in naphthalene and PETN crystals  

NASA Astrophysics Data System (ADS)

We have developed a computational approach that yields anharmonic vibrational couplings in molecular crystals. The approach is based on anharmonic vibrational potential-energy surface reconstruction starting from a normal-mode vibrational basis. The method was implemented for semiempirical Hamiltonians with periodic boundary conditions, with applications to crystalline naphthalene and pentaerythritol tetranitrate. For each material, we predicted infrared and Raman linewidths, and vibrational anharmonic couplings associated with up- and down-conversions, as well as pure-dephasing processes. Comparison is made to experimental data for Raman linewidths and averaged anharmonic couplings; reasonable agreement is obtained, suggesting that implementation of the method within a first-principles electronic structure framework is warranted.

Piryatinski, Andrei; Tretiak, Sergei; Sewell, Thomas D.; McGrane, Shawn D.

2007-06-01

269

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)

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 Mřller-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 A?, 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 A? 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.

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

2013-09-01

270

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

NASA Astrophysics Data System (ADS)

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 Mřller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix.

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

2011-09-01

271

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

PubMed

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 Mřller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix. PMID:21932876

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

2011-09-14

272

Modeling Vibrational Structure Using Harmonically-Coupled Morse Oscillators: a Global Description of the C-H Stretches in Methyl Radical and its Deuterated Isotopomers  

NASA Astrophysics Data System (ADS)

Methyl radical has been the subject of numerous theoretical and experimental studies over the past 50 years, including several studies fitting force constants to experimental data. Only recently have high-resolution gas phase data become available for most of the stretches of all four isotopic species: CH_3, CH_2D, CHD_2, and CD_3. A harmonically-coupled Morse oscillator model, developed by Halonen and Child for tetrahedral molecules, is used to describe the set of high resolution data for the first time. In this picture, each C-H (or C-D) stretch is modeled as a Morse oscillator and the interactions between the local mode stretches are modeled as harmonic interactions. The C-H and C-D stretches differ only by analytic G-matrix element terms thus making this a three parameter model that describes each of the three stretches for all four isotopic species, where the parameters are the Morse oscillator dissociation energy (D), the range parameter (a), and the harmonic potential coupling constant. L. Halonen and M. S. Child Mol. Phys. 46, 239 (1982).

Roberts, Melanie A.; Nesbitt, David J.; McCoy, Anne B.

2011-06-01

273

Ecient Calculation of Fluid Structure Interaction in Ship Vibration Alexander MenkMark Wilkeny Christian Cabosz Heinrich Vossx  

Microsoft Academic Search

Because of its high mass density, water has a signicant impact on vibrations of ship structures and uid-structure interaction has to be considered in an accurate modeling of global ship vibration. In this presentation we discuss an approach for including the eect of water in such simulations eciently.

Robert Bosch

274

Structure of Au4 (0?-1) in the gas phase: A joint geometry relaxed ab initio calculations and vibrationally resolved photoelectron imaging investigation.  

PubMed

We have combined photoelectron velocity-map imaging spectroscopy and high-level ab initio calculations to elucidate the geometries of Au4 (0?-1). Well-resolved ground-state electronic transition was observed in the photoelectron spectrum of Au4 (-) at 446 nm, leading to more accurate electron affinity and vibrational frequencies for the ground state of the neutral Au4 (-). The pure and vibrationally resolved spectra provide definitive experimental evidence for the resolution of the ground-state gold tetramer in the gaseous phase, with the aid of the ab initio calculations and Franck-Condon simulations. The comprehensive comparisons between the experiment and theoretical calculations suggest that the Y-shaped structure is the global minimum for both the neutral and anionic Au4. PMID:24028116

Liu, Zhiling; Qin, Zhengbo; Xie, Hua; Cong, Ran; Wu, Xia; Tang, Zichao

2013-09-01

275

Ab initio calculation of Raman vibrational signatures of 2,4-dinitrotoluene, 2,6-dinitrotoluene and 2,4,6-trinitrotoluene  

NASA Astrophysics Data System (ADS)

The Raman vibrational frequencies in the finger print region (700-1600 cm-1) have been calculated for 2,4- dinitrotoluene, 2,6-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT). The Raman vibrational intensities and frequencies for these molecules have been calculated using B3LYP Density Functional Theory method with 6-311+G** and Sadlejs medium-sized polarized basis sets (Sadlej pVTZ). The normal mode assignments in the finger print region were carried out by Normal Coordinate Analysis, where localized and de-localized coordinates were used to facilitate an accurate description of the vibrational modes. The Raman intensities were calculated from the Raman scattering cross sections using the ab initio calculated Raman scattering activities. Comparison of these intensities using different basis sets indicates that the Sadlej pVTZ basis sets increase the calculated intensities for the NO2 symmetric stretching and bending frequencies by more than 15 % relative to 6-311+G** basis. The potential energy distribution for the symmetric and asymmetric NO2 stretches indicates that 2-NO2 and 6-NO2 couple strongly in 2,6-DNT and 2,4,6-TNT, while 2-NO2 and 4-NO2 groups couple weakly in 2,4- DNT. These findings suggest that the coupling strength of 2-NO2, 6-NO2 and 4-NO2 groups can be used to distinguish between dinitro and trinitro toluenes.

Castillo-Chará, Jairo; Manrique-Bastidas, César; Mina, Nairmen; Castro, Miguel E.; Hernández-Rivera, Samuel P.

2007-10-01

276

Non-Linear Correction of Vibration Protection System Containing Tuned Dynamic Absorber  

NASA Astrophysics Data System (ADS)

In this paper, the system of vibration protection containing the tuned dynamic absorber is analyzed. To control the system's extraneous resonant responses without affecting the ability of essential linear vibration suppression at antiresonant frequency, the absolute motion of the absorber is limited by the stops mounted upon the base. The analytical solution relies on the theory of momentary impact and technique of periodic Green functions and is obtained in explicit closed form. The frequency responses of the vibration protection system under harmonic excitation with variable frequency are obtained in terms of impact impulses, magnitudes of fundamental harmonics of motion for the primary and secondary systems and also the forces transmitted to the base. The results of calculations are in good agreement with a numerical simulation, which utilizes the realistic model of visco-elastic collision. Some general concepts of practical design of such a vibration protection system are discussed. In particular, the influences of restitution ratio and clearance value are addressed.

Veprik, A. M.; Babitsky, V. I.

2001-01-01

277

Efficient and automatic calculation of optical band shapes and resonance Raman spectra for larger molecules within the independent mode displaced harmonic oscillator model.  

PubMed

In this work, an improved method for the efficient automatic simulation of optical band shapes and resonance Raman (rR) intensities within the "independent mode displaced harmonic oscillator" is described. Despite the relative simplicity of this model, it is able to account for the intensity distribution in absorption (ABS), fluorescence, and rR spectra corresponding to strongly dipole allowed electronic transitions with high accuracy. In order to include temperature-induced effects, we propose a simple extension of the time dependent wavepacket formalism developed by Heller which enables one to derive analytical expressions for the intensities of hot bands in ABS and rR spectra from the dependence of the wavepacket evolution on its initial coordinate. We have also greatly optimized the computational procedures for numerical integration of complicated oscillating integrals. This is important for efficient simulations of higher-order rR spectra and excitation profiles, as well as for the fitting of experimental spectra of large molecules. In particular, the multimode damping mechanism is taken into account for efficient reduction of the upper time limit in the numerical integration. Excited state energy gradient as well as excited state geometry optimization calculations are employed in order to determine excited state dimensionless normal coordinate displacements. The gradient techniques are highly cost-effective provided that analytical excited state derivatives with respect to nuclear displacements are available. Through comparison with experimental spectra of some representative molecules, we illustrate that the gradient techniques can even outperform the geometry optimization method if the harmonic approximation becomes inadequate. PMID:23267471

Petrenko, Taras; Neese, Frank

2012-12-21

278

The effect of an infinite plane-wave approximation on calculations for second-harmonic generation in a one-dimensional nonlinear crystal  

NASA Astrophysics Data System (ADS)

In this paper, the second-harmonic generation (SHG) in a one-dimensional nonlinear crystal that is embedded in air is investigated. Previously, the identical configuration was studied in Li Z. Y. et al., Phys. Rev. B, 60 (1999) 10644, without the use of the slowly varying amplitude approximation (SVAA), but by adopting the infinite plane-wave approximation (PWA), despite the fact that this approximation is not quite applicable to such a system. We calculate the SHG conversion efficiency without a PWA, and compare the results with those from the quoted reference. The investigation reveals that conversion efficiencies of SHG as calculated by the two methods appear to exhibit significant differences, and that the SHG may be modulated by the field of a fundamental wave (FW). The ratio between SHG conversion efficiencies as produced by the two methods shows a periodic variation, and this oscillatory behavior is fully consistent with the variation in transmittance of the FW. Quasi-phase matching (QPM) is also studied, and we find that the location of the peak for SHG conversion efficiency deviates from ?d=0, which differs from the conventional QPM results.

Zhao, Jing; Zhao, Li-Ming

2012-05-01

279

Regulatory Harmonization  

Center for Biologics Evaluation and Research (CBER)

. The Agency engages in a range of explicit harmonization initiatives, a subset of which includes the participation of CBER. ... More results from www.fda.gov/biologicsbloodvaccines/internationalactivities

280

Modeling of the influence of conformation, isotopic substitution, and aqueous environment on the vibrational spectrum of L-glutamic acid  

NASA Astrophysics Data System (ADS)

Quantum-mechanical calculations of optimized structures, harmonic force fields, and vibrational spectra were performed for 10 L-glutamic acid conformers. The vibrational spectra were interpreted using B3LYP/6-31+G** calculations for the stablest conformer. Satisfactory agreement between the experimental and theoretical data was obtained. Vibrational frequency shifts caused by isotopic substitution of various types in the L-glutamic acid molecule were analyzed taking into account the conformational structure and the influence of water medium and molecule ionization. Isotopic tags are suggested that can be used in biochemical studies taking into account their special characteristics.

Dotsenko, G. S.; Kuramshina, G. M.; Pentin, Yu. A.

2010-07-01

281

Infrared spectra of permanganate anions in potassium perchlorate matrices: vibrational anharmonicity, effective symmetry and vibrational mode mixing effects  

Microsoft Academic Search

Fourier transform infrared spectra of MnO4? anions isomorphously isolated in potassium perchlorate matrices were recorded at room and low temperature (LT, ?100 K). On the basis of the detected second-order vibrational transitions involving the dopant species ?3 mode components, anharmonicity constants and harmonic eigenvalues for these modes were calculated. Despite the fact that, rigorously speaking, the appearance of the spectra

Ljup?o Pejov; Vladimir M. Petruševski

2002-01-01

282

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

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.

McGuire, John Andrew

2004-11-24

283

Currents and vibrations in asynchronous motor with externally induced vibration  

Microsoft Academic Search

This paper presents an experimental investigation of the airgap variation model for vibration and current harmonics relationship in induction motors. To this aim, an external vibra- tion source was employed, together with ball bearing alterations in order to decrease stiffness. The direction of the external vibration is radial with respect to the axis of the electric machine under test. To

Fabio Immovilli; Claudio Bianchini; Marco Cocconcelli; Alberto Bellini; Riccardo Rubini

2011-01-01

284

Complex Vibrational Analysis of an Antiferroelectric Liquid Crystal Based on Solid-State Oriented Quantum Chemical Calculations and Experimental Molecular Spectroscopy.  

PubMed

The experimental and theoretical vibrational spectroscopic study of one of a novel antiferroelectric liquid crystals (AFLC), known under the MHPSBO10 acronym, have been undertaken. The interpretation of both FT-IR and FT-Raman spectra was focused mainly on the solid-state data. To analyze the experimental results along with the molecular properties, density functional theory (DFT) computations were performed using several modern theoretical approaches. The presented calculations were performed within the isolated molecule model, probing the performance of modern exchange-correlations functionals, as well as going beyond, i.e., within hybrid (ONIOM) and periodic boundary conditions (PBC) methodologies. A detailed band assignment was supported by the normal-mode analysis with SQM ab initio force field scaling. The results are supplemented by the noncovalent interactions analysis (NCI). The relatively noticeable spectral differences observed upon Crystal to AFLC phase transition have also been reported. For the most prominent vibrational modes, the geometries of the transition dipole moments along with the main components of vibrational polarizability were analyzed in terms of the molecular frame. One of the goals of the paper was to optimize the procedure of solid-state calculations to obtain the results comparable with the all electron calculations, performed routinely for isolated molecules, and to test their performance. The presented study delivers a complex insight into the vibrational spectrum with a noticeable improvement of the theoretical results obtained for significantly attracting mesogens using modern molecular modeling approaches. The presented modeling conditions are very promising for further description of similar large molecular crystals. PMID:22709148

Dru?bicki, Kacper; Mikuli, Edward; Kocot, Antoni; Ossowska-Chru?ciel, Miros?awa Danuta; Chru?ciel, Janusz; Zalewski, S?awomir

2012-07-19

285

Harmonic frequency scaling factors for Hartree-Fock, S-VWN, B-LYP, B3-LYP, B3PW91 and MP2 with the Sadlej pVTZ electric property basis set  

Microsoft Academic Search

.   Scaling factors for obtaining fundamental vibrational frequencies from harmonic frequencies calculated at six of the most\\u000a commonly used levels of theory have been determined from regression analysis for the polarized-valence triple-zeta (pVTZ)\\u000a Sadlej electric property basis set. The Sadlej harmonic frequency scaling factors for first- and second-row molecules were\\u000a derived from a comparison of a total of 900 individual

Mathew D. Halls; Julia Velkovski; H. Bernhard Schlegel

2001-01-01

286

Calculation of the interaction potential energy curve and vibrational levels for the a3?u+ state of Li27 molecule  

NASA Astrophysics Data System (ADS)

We solve the Schrödinger equation with the improved expression of the Manning–Rosen empirical potential energy model. The rotation-vibrational energy spectra and the unnormalized radial wave functions have been obtained. The interaction potential energy curve for the a3?u+ state of Li27 molecule is modeled by employing Manning–Rosen potential model. Favorable agreement for the Manning–Rosen potential is found in comparing with ab initio data. The vibrational energy levels predicted by using the Manning–Rosen potential for the a3?u+ state of Li27 are in good agreement with the RKR data and ab initio determinations.

Liu, Jian-Yi; Zhang, Guang-Dong; Jia, Chun-Sheng

2013-09-01

287

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

ERIC Educational Resources Information Center

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…

Fang, Tian-Shen

2007-01-01

288

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

ERIC Educational Resources Information Center

|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…

Fang, Tian-Shen

2007-01-01

289

The evolution of harmonic Indian musical drums: A mathematical perspective  

NASA Astrophysics Data System (ADS)

We explain using mathematics how harmonic musical drums were discovered by Indian artisans and musicians more than 2000 years ago. To this end, we introduce a harmonic error function which measures the quality of the harmonic relationship and degeneracy of the first modes of vibration of a centrally symmetric loaded membrane. We explain that although the tabla configuration found by the ancient Indians is the most natural one, other configurations exist and some are harmonically superior to the classical one.

Gaudet, Samuel; Gauthier, Claude; Léger, Sophie

2006-03-01

290

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 Astrophysics Data System (ADS)

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.

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

1993-07-01

291

Comparison of the performance of different DFT methods in the calculations of the molecular structure and vibration spectra of serotonin (5-hydroxytryptamine, 5-HT)  

NASA Astrophysics Data System (ADS)

Serotonin (5-hydroxytryptamine, 5-HT) is a monoamine neurotransmitter which plays an important role in treating acute or clinical stress. The comparative performance of different density functional theory (DFT) methods at various basis sets in predicting the molecular structure and vibration spectra of serotonin was reported. The calculation results of different methods including mPW1PW91, HCTH, SVWN, PBEPBE, B3PW91 and B3LYP with various basis sets including LANL2DZ, SDD, LANL2MB, 6-31G, 6-311++G and 6-311+G\\midast were compared with the experimental data. It is remarkable that the SVWN/6-311++G and SVWN/6-311+G\\midast levels afford the best quality to predict the structure of serotonin. The results also indicate that PBEPBE/LANL2DZ level show better performance in the vibration spectra prediction of serotonin than other DFT methods.

Yang, Yue; Gao, Hongwei

2012-04-01

292

Hydrogen transfer in photo-excited phenol/ammonia clusters by UV-IR-UV ion dip spectroscopy and ab initio molecular orbital calculations. II. Vibrational transitions  

NASA Astrophysics Data System (ADS)

The vibrational spectra of phenol/ammonia clusters (1:2-5) in S0 and those of their photochemical reaction products, (NH3)n-1NH4 (n=2-5), which are generated by excited-state hydrogen transfer, have been measured by UV-IR-UV ion dip spectroscopy. The geometries, IR spectra and normal modes of phenol-(NH3)n (n=1-5) have been examined by ab initio molecular orbital calculations, at the second-order Mřller-Plesset perturbation theory level with large basis sets. For the n=2 and 3 reaction products, similar vibrational analyses have been carried out. From the geometrical information of reactants and products, it has been suggested that the reaction products have memories of the reactant's structure, which we call ``memory effect.''

Ishiuchi, Shun-Ichi; Daigoku, Kota; Saeki, Morihisa; Sakai, Makoto; Hashimoto, Kenro; Fujii, Masaaki

2002-10-01

293

Variational Calculations of Vibrational Energies and IR Spectra of trans- and cis-HOCO Using New ab Initio Potential Energy and Dipole Moment Surfaces  

NASA Astrophysics Data System (ADS)

We report ab initio potential energy and dipole moment surfaces that span the regions describing the minima of trans- and cis-HOCO and the barrier separating them. We use the new potential in three types of variational calculations of the vibrational eigenstates, for zero total angular momentum. Two use the code MULTIMODE (MM) in the so-called single-reference and reaction path versions. The third uses the exact Hamiltonian in diatom-diatom Jacobi coordinates. The single-reference version of MM is limited to a description of states that are localized at each minimum separately, whereas the reaction-path version and the Jacobi approach describe localized and delocalized states. The vibrational IR spectrum for zero total angular momentum is also reported for the trans and cis fundamentals and selected overtone and combination states with significant oscillator strength.

Wang, Yimin; Carter, Stuart; Bowman, Joel M.

2013-10-01

294

Calculations of nonlinear wave-packet interferometry signals in the pump-probe limit as tests for vibrational control over electronic excitation transfer.  

PubMed

The preceding paper [J. D. Biggs and J. A. Cina, J. Chem. Phys. 131, 224101 (2009)] (referred to here as Paper 1), describes a strategy for externally influencing the course of short-time electronic excitation transfer (EET) in molecular dimers and observing the process by nonlinear wave-packet interferometry (nl-WPI). External influence can, for example, be exerted by inducing coherent intramolecular vibration in one of the chromophores prior to short-pulse electronic excitation of the other. Within a sample of isotropically oriented dimers having a specified internal geometry, a vibrational mode internal to the acceptor chromophore can be preferentially driven by electronically nonresonant impulsive stimulated Raman (or resonant infrared) excitation with a short polarized "control" pulse. A subsequent electronically resonant polarized pump then preferentially excites the donor, and EET ensues. Paper 1 investigates control-pulse-influenced nl-WPI as a tool for the spectroscopic evaluation of the effect of coherent molecular vibration on excitation transfer, presenting general expressions for the nl-WPI difference signal from a dimer following the action of a control pulse of arbitrary polarization and shape. Electronic excitation is to be effected and its interchromophore transfer monitored by resonant pump and probe "pulses," respectively, each consisting of an optical-phase-controlled ultrashort pulse-pair having arbitrary polarization, duration, center frequency, and other characteristics. Here we test both the control strategy and its spectroscopic investigation-with some sacrifice of amplitude-level detail-by calculating the pump-probe difference signal. That signal is the limiting case of the control-influenced nl-WPI signal in which the two pulses in the pump pulse-pair coincide, as do the two pulses in the probe pulse-pair. We present calculated pump-probe difference signals for (1) a model excitation-transfer complex in which two equal-energy monomers each support one moderately Franck-Condon active intramolecular vibration; (2) a simplified model of the covalent dimer dithia-anthracenophane, representing its EET dynamics following selective impulsive excitation of the weakly Franck-Condon active nu(12) anthracene vibration at 385 cm(-1); and (3) a model complex featuring moderate electronic-vibrational coupling in which the site energy of the acceptor chromophore is lower than that of the donor. PMID:20001031

Biggs, Jason D; Cina, Jeffrey A

2009-12-14

295

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)

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.

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

2013-10-01

296

Multi-Frequency Harmonics Technique for HIFU Tissue Treatment  

NASA Astrophysics Data System (ADS)

New technique for enhancing of tissue lysis and enlarging treatment volume during one HIFU sonification is proposed. The technique consists in simultaneous or alternative (at optimal repetition frequency) excitation of single element HIFU transducer on a frequencies corresponding to odd natural harmonics of piezoceramic element at ultrasound energy levels sufficient for producing cavitational, thermal or mechanical damage of fat cells at each of aforementioned frequencies. Calculation and FEM modeling of transducer vibrations and acoustic field patterns for different frequencies sets were performed. Acoustic pressure in focal plane was measured in water using calibrated hydrophone and 3D acoustic scanning system. In vitro experiments on different tissues and phantoms confirming the advantages of multifrequency harmonic method were performed.

Rybyanets, Andrey N.; Lugovaya, Maria A.; Rybyanets, Anastasia A.

2010-03-01

297

Ethylenediammonium dication: H-bonded complexes with terephthalate, chloroacetate, phosphite, selenite and sulfamate anions. Detailed vibrational spectroscopic and theoretical studies of ethylenediammonium terephthalate.  

PubMed

Crystalline complexes between ethylenediammonium dication and terephthalate, chloroacetate, phosphite, selenite and sulfamate anions were obtained by slow evaporation from water solution method. Room temperature powder infrared and Raman measurements were carried out. For ethylenediammonium terephthalate theoretical calculations of structure were performed by two ways: ab-initio HF and semiempirical PM3. In this case the PM3 method gave more accurate structure (closer to X-ray results). The additional PM3 calculations of vibrational spectra were performed. On the basis theoretical approach and earlier vibrational studies of similar compounds the vibrational assignments for observed bands have been proposed. All compounds were checked for second harmonic generation (SHG). PMID:23078789

Marchewka, M K; Drozd, M

2012-09-24

298

Structure, stability, depolarized light scattering, and vibrational spectra of fullerenols from all-electron density-functional-theory calculations  

Microsoft Academic Search

We have investigated the stability, electronic properties, Rayleigh (elastic), and Raman (inelastic) depolarization ratios, infrared and Raman absorption vibrational spectra of fullerenols [C60(OH)n] with different degrees of hydroxylation by using all-electron density-functional-theory (DFT) methods. Stable arrangements of these molecules were found by means of full geometry optimizations using Becke's three-parameter exchange functional with the Lee, Yang, and Parr correlation functional.

Roberto Rivelino; Thaciana Malaspina; Eudes E. Fileti

2009-01-01

299

Application of the generalized Euler series transformation for calculation of vibration-rotation energy levels of diatomic molecules  

NASA Astrophysics Data System (ADS)

The detailed spectroscope information about highly excited molecules and radicals such us as H+3, H2, HI, H2O, CH2 is needed for a number of applications in the field of laser physics, astrophysics and chemistry. Studies of highly excited molecular vibration-rotation states face several problems connected with slowly convergence or even divergences of perturbation expansions. The physical reason for a perturbation expansion divergence is the large amplitude motion and strong vibration-rotation coupling. In this case one needs to use the special method of series summation. There were a number of papers devoted to this problem: papers 1-10 in the reference list are only example of studies on this topic. The present report is aimed at the application of GET method (Generalized Euler Transformation) to the diatomic molecule. Energy levels of a diatomic molecule is usually represented as Dunham series on rotational J(J+1) and vibrational (V+1/2) quantum numbers (within the perturbation approach). However, perturbation theory is not applicable for highly excited vibration-rotation states because the perturbation expansion in this case becomes divergent. As a consequence one need to use special method for the series summation. The Generalized Euler Transformation (GET) is known to be efficient method for summing of slowly convergent series, it was already used for solving of several quantum problems Refs.13 and 14. In this report the results of Euler transformation of diatomic molecule Dunham series are presented. It is shown that Dunham power series can be represented of functional series that is equivalent to its partial summation. It is also shown that transformed series has the butter convergent properties, than the initial series.

Kruglova, T. V.

2004-01-01

300

Analysis of UV and vibrational spectra (FT-IR and FT-Raman) of hexachlorocyclotriphosphazene based on normal coordinate analysis, MP2 and DFT calculations  

NASA Astrophysics Data System (ADS)

The Raman (1400-100 cm-1) and infrared (4000-400 cm-1) of solid hexachlorocyclotriphosphazene, P3N3Cl6 (HCCTP) were recorded. The conformational energies were calculated using MP2 and DFT (B3LYP and B3PW91) methods utilizing a variety of basis sets up to 6-311+G(d). On the basis of D3h symmetry, the simulated vibrational spectra of P3N3Cl6 from MP2 and DFT methods were in excellent agreement with those obtained experimentally. Additionally, Frontier Molecular Orbitals and electronic transitions were predicted using steady state and time dependent DFT(B3LYP)/PCM calculations respectively, each employing the 6-311+G(d,p) optimized structural parameters. The predicted wavelengths were in excellent agreement with experimental values when CH2Cl2 was used as solvent. The 14N and 31P chemical shifts were predicted with B3LYP/6-311+G(2d,p) calculations using the GIAO technique with solvent effect modeled using the PCM method. The computed structural parameters of the planar P3N3Cl6 (D3h) agree well with experimental values from both X-ray and electron diffraction data with slight distortions observed due to lattice defects in the solid phase. The experimental/computational results favor a slightly distorted D3h symmetry for the title compound in the gas and solid phases and in solution (?PNPN and ?NPNP ranged from 0.018° to 0.90°). Aided by normal coordinate analysis, and the simulated vibrational spectra utilizing MP2, B3LYP and B3PW91 methods at 6-31G(d) basis set, revised and complete vibrational assignments for all fundamentals are provided herein.

Zoghaib, Wajdi M.; Husband, John; Soliman, Usama A.; Shaaban, Ibrahim A.; Mohamed, Tarek A.

2013-03-01

301

On simple, accurate calculations of atomic charges, bond properties and molecular energies. IV. Butane gauche interactions and vibrational energies of alkylcyclohexanes and related polycyclic hydrocarbons  

Microsoft Academic Search

The vibrational frequencies of selected alkylcyclohexanes and related polycyclic molecules consisting of chair and boat six-membered rings were calculated using conventional Hartree–Fock theory with a 6-31G(d) basis and a hybrid density functional procedure (B3LYP) with a standard 6-311G(d,p) basis. Appropriate scale factors were determined. The sums of zero-point (ZPE) and heat-content (HT?H0) energies thus obtained are well reproduced by an

S. Fliszár; E. C. Vauthier; S. Chrétien

2004-01-01

302

Calculation of the Transition from Pairing Vibrational to Pairing Rotational Regimes between Magic Nuclei {sup 100}Sn and {sup 132}Sn via Two-Nucleon Transfer Reactions  

SciTech Connect

Absolute values of two-particle transfer cross sections along the Sn-isotopic chain are calculated. They agree with measurements within errors and without free parameters. Within this scenario, the predictions concerning the absolute value of the two-particle transfer cross sections associated with the excitation of the pairing vibrational spectrum expected around the recently discovered closed shell nucleus {sub 50}{sup 132}Sn{sub 82} and the very exotic nucleus {sub 50}{sup 100}Sn{sub 50} can be considered quantitative, opening new perspectives in the study of pairing in nuclei.

Potel, G.; Barranco, F.; Marini, F.; Idini, A.; Vigezzi, E.; Broglia, R. A. [Departamento de Fisica Atomica, Molecular y Nuclear y Departamento de Fisica Aplicada III, Universidad de Sevilla (Spain); INFN, Sezione di Milano and Departimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milano (Italy)

2011-08-26

303

Vibrations and hydrogen bonding in porphycene.  

PubMed

Combined use of IR, Raman, neutron scattering and fluorescence measurements for porphycene isolated in helium nanodroplets, supersonic jet and cryogenic matrices, as well as for solid and liquid solutions, resulted in the assignments of almost all of 108 fundamental vibrations. The puzzling feature of porphycene is the apparent lack of the N-H stretching band in the IR spectrum, predicted to be the strongest of all bands by standard harmonic calculations. Theoretical modeling of the IR spectra, based on ab initio molecular dynamics simulations, reveals that the N-H stretching mode should appear as an extremely broad band in the 2250-3000 cm(-1) region. Coupling of the N-H stretching vibration to other modes is discussed in the context of multidimensional character of intramolecular double hydrogen transfer in porphycene. The analysis can be generalized to other strongly hydrogen-bonded systems. PMID:22415158

Gawinkowski, Sylwester; Walewski, ?ukasz; Vdovin, Alexander; Slenczka, Alkwin; Rols, Stephane; Johnson, Mark R; Lesyng, Bogdan; Waluk, Jacek

2012-03-13

304

Dynamic Analysis of Wind Turbine Planetary Gears Using an Extended Harmonic Balance Approach: Preprint  

SciTech Connect

The dynamics of wind turbine planetary gears with gravity effects are investigated using an extended harmonic balance method that extends established harmonic balance formulations to include simultaneous internal and external excitations. The extended harmonic balance method with arc-length continuation and Floquet theory is applied to a lumped-parameter planetary gear model including gravity, fluctuating mesh stiffness, bearing clearance, and nonlinear tooth contact to obtain the planetary gear dynamic response. The calculated responses compare well with time domain integrated mathematical models and experimental results. Gravity is a fundamental vibration source in wind turbine planetary gears and plays an important role in system dynamics, causing hardening effects induced by tooth wedging and bearing-raceway contacts. Bearing clearance significantly reduces the lowest resonant frequencies of translational modes. Gravity and bearing clearance together lowers the speed at which tooth wedging occurs lower than the resonant frequency.

Guo, Y.; Keller, J.; Parker, R. G.

2012-06-01

305

Theoretical study of high-order-harmonic generation from asymmetric diatomic molecules  

NASA Astrophysics Data System (ADS)

The molecular high-order-harmonic generation (molecular HHG) of HeH2+ is investigated by numerical integration of the non-Born-Oppenheimer time-dependent Schrödinger equation. The results show that multichannel interference plays a very important role in the process of asymmetric molecular high-order-harmonic generation. By means of the classical returning kinetic energy map and the time-frequency distribution, the mechanism of molecular HHG for HeH2+ is discussed in detail. Further studies show that asymmetric molecular harmonic emission is very sensitive to the nuclear signatures, i.e., the initial vibrational state and the isotopic effect. Besides, the electron-nuclear probability density distributions are calculated to better understand the process of the asymmetric molecular HHG, from which the electron-nuclear dynamics can be revealed.

Miao, Xiang-Yang; Du, Hui-Ni

2013-05-01

306

Calculation of the structure, potential energy surface, vibrational dynamics, and electric dipole properties for the Xe:HI van der Waals complex  

NASA Astrophysics Data System (ADS)

We report the structure and spectroscopic characteristics for the Xe:HI van der Waals binary isomers determined from variational solutions of two-dimensional and three-dimensional (3D) vibrational Schrödinger equations. The solutions are based on a potential energy surface computed at the coupled-cluster level of theory including single and double excitations and a non-iterative perturbation treatment of triple excitations [CCSD(T)]. The dipole moment surface was calculated using quadratic configuration interaction (QCISD). The global potential minimum is shown to be located at the anti-hydrogen-bonded Xe-IH isomer, 21 cm-1 below the secondary local minimum associated with the hydrogen-bonded Xe-HI isomeric form. The dissociation energy from the global minimum is 245.9 cm-1. 3D Schrödinger equations are solved for the rotational quantum numbers J = k = 0, 1, and 2, without invoking an adiabatic separation of high- and low-frequency degrees of freedom. The vibrational ground state resides in the Xe-HI potential well, while the first excited state, 8.59 cm-1 above the ground, occupies the Xe-IH well. We find that intra-complex dynamics exhibits a sudden transformation upon increase of the r(HI) bond length, accompanied by abrupt changes in the geometric and dipole parameters. A similar chaotic behavior is predicted to occur for Xe:DI at a shorter r(DI) bond length, which implies stronger coupling between low- and high-frequency motions in the heavier complex. Our calculations confirm a strong enhancement for the r(HI) stretch fundamental and a significant weakening for the first overtone vibrational transitions in Xe:HI, as compared to those in the free HI molecule. A qualitative explanation of this, earlier experimentally detected effect is suggested.

Preller, M.; Grunenberg, J.; Bulychev, V. P.; Bulanin, M. O.

2011-05-01

307

Calculation of the fundamental vibrational frequencies and intensities of H2, D2, and N2 in the presence of Li(+) or Na  

NASA Astrophysics Data System (ADS)

Self-consistent-field (SCF) and second-order Moller-Plesset (MP2) calculations, using large basis sets, have been carried out for the system X2...Y(+), with X = H, D, and N and Y = Li and Na. In particular, the fundamental vibrational frequency shifts and intensities induced in the diatomic by the cation have been found. For Y = Na these properties may be compared with the experimental infrared spectra of the same diatomics when trapped in a NaA zeolite. There is good agreement between theory and experiment for the frequency shifts but the calculated intensity for N2...Na(+) is several times larger than that found in the zeolite. This indicates that either the model for the trapped species is too simple or the experimental result needs reassessment.

Bishop, David M.; Cybulski, Slawomir M.

1994-11-01

308

Harmonic generation at high intensities  

SciTech Connect

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.

Schafer, K.J.; Krause, J.L.; Kulander, K.C.

1993-06-01

309

Anharmonic force field and vibrational dynamics of CH2F2 up to 5000 cm-1 studied by Fourier transform infrared spectroscopy and state-of-the-art ab initio calculations  

NASA Astrophysics Data System (ADS)

Difluoromethane (CH2F2, HFC-32) is a molecule used in refrigerant mixtures as a replacement of the more environmentally hazardous, ozone depleting, chlorofluorocarbons. On the other hand, presenting strong vibration-rotation bands in the 9 ?m atmospheric window, it is a greenhouse gas which contributes to global warming. In the present work, the vibrational and ro-vibrational properties of CH2F2, providing basic data for its atmospheric modeling, are studied in detail by coupling medium resolution Fourier transform infrared spectroscopy to high-level electronic structure ab initio calculations. Experimentally a full quantum assignment and accurate integrated absorption cross sections are obtained up to 5000 cm-1. Ab initio calculations are carried out by using CCSD(T) theory and large basis sets of either the correlation consistent or atomic natural orbital hierarchies. By using vibrational perturbation theory to second order a complete set of vibrational and ro-vibrational parameters is derived from the ab initio quartic anharmonic force fields, which well compares with the spectroscopic constants retrieved experimentally. An excellent agreement between theory and experiment is achieved for vibrational energy levels and integrated absorption cross sections: transition frequencies up to four quanta of vibrational excitation are reproduced with a root mean square deviation (RMSD) of 7 cm-1 while intensities are predicted within few km mol-1 from the experiment. Basis set performances and core correlation effects are discussed throughout the paper. Particular attention is focused in the understanding of the anharmonic couplings which rule the vibrational dynamics of the |?1>, |2?8>, |2?2> three levels interacting system. The reliability of the potential energy and dipole moment surfaces in reproducing the vibrational eigenvalues and intensities as well as in modeling the vibrational and ro-vibrational mixings over the whole 400-5000 cm-1 region is also demonstrated by spectacular spectral simulations carried out by using the ro-vibrational Hamiltonian constants, and the relevant coupling terms, obtained from the perturbation treatment of the ab initio anharmonic force field. The present results suggest CH2F2 as a prototype molecule to test ab initio calculations and theoretical models.

Tasinato, Nicola; Regini, Giorgia; Stoppa, Paolo; Charmet, Andrea Pietropolli; Gambi, Alberto

2012-06-01

310

Anharmonic force field and vibrational dynamics of CH2F2 up to 5000 cm(-1) studied by Fourier transform infrared spectroscopy and state-of-the-art ab initio calculations.  

PubMed

Difluoromethane (CH(2)F(2), HFC-32) is a molecule used in refrigerant mixtures as a replacement of the more environmentally hazardous, ozone depleting, chlorofluorocarbons. On the other hand, presenting strong vibration-rotation bands in the 9 ?m atmospheric window, it is a greenhouse gas which contributes to global warming. In the present work, the vibrational and ro-vibrational properties of CH(2)F(2), providing basic data for its atmospheric modeling, are studied in detail by coupling medium resolution Fourier transform infrared spectroscopy to high-level electronic structure ab initio calculations. Experimentally a full quantum assignment and accurate integrated absorption cross sections are obtained up to 5000 cm(-1). Ab initio calculations are carried out by using CCSD(T) theory and large basis sets of either the correlation consistent or atomic natural orbital hierarchies. By using vibrational perturbation theory to second order a complete set of vibrational and ro-vibrational parameters is derived from the ab initio quartic anharmonic force fields, which well compares with the spectroscopic constants retrieved experimentally. An excellent agreement between theory and experiment is achieved for vibrational energy levels and integrated absorption cross sections: transition frequencies up to four quanta of vibrational excitation are reproduced with a root mean square deviation (RMSD) of 7 cm(-1) while intensities are predicted within few km mol(-1) from the experiment. Basis set performances and core correlation effects are discussed throughout the paper. Particular attention is focused in the understanding of the anharmonic couplings which rule the vibrational dynamics of the |?(1)>, |2?(8)>, |2?(2)> three levels interacting system. The reliability of the potential energy and dipole moment surfaces in reproducing the vibrational eigenvalues and intensities as well as in modeling the vibrational and ro-vibrational mixings over the whole 400-5000 cm(-1) region is also demonstrated by spectacular spectral simulations carried out by using the ro-vibrational Hamiltonian constants, and the relevant coupling terms, obtained from the perturbation treatment of the ab initio anharmonic force field. The present results suggest CH(2)F(2) as a prototype molecule to test ab initio calculations and theoretical models. PMID:22697538

Tasinato, Nicola; Regini, Giorgia; Stoppa, Paolo; Pietropolli Charmet, Andrea; Gambi, Alberto

2012-06-01

311

Factorial design and principal component analyses of the vibrational frequencies and infrared intensities of methane and silane  

Microsoft Academic Search

A multivariate statistical approach is presented to analyze the changes in calculated harmonic vibrational frequencies and infrared intensities obtained from ab initio calculations for methane and silane. The effects of four wave function modifications on these spectral parameters are investigated using a two-level factorial design and principal component analyses: basis set (6-31G and 6-311G), inclusion of polarization and diffuse functions

Anselmo E. de Oliveira; Roy E. Bruns

1997-01-01

312

Vibrational overtone stretching transitions in sarin  

NASA Astrophysics Data System (ADS)

The CH stretching overtone transitions of the nerve agent sarin (O-isopropyl methylphosphonofluoridate) are of interest to the standoff detection of chemical warfare agents, as many of these transitions occur near regions where small, efficient, portable diode lasers (originally developed for use in the telecommunications industry) operate. However, the interpretation of experimental vibrational overtone spectra is often difficult, and the computational simulation of overtone transitions in a molecule is challenging. Presented herein are the simulated CH overtone stretching transitions in sarin. Spectral regions are simulated from overtone transition energies and intensities, both of which are calculated within the harmonically coupled anharmonic oscillator (HCAO) model. Data for HCAO calculations are obtained from ab initio calculations, without any recourse to experimental data.

Petryk, Michael W. P.

2006-10-01

313

Structural and vibrational spectral investigations of melaminium maleate monohydrate by FTIR, FT-Raman and quantum chemical calculations.  

PubMed

The structural investigations of the molecular complex of melamine with maleic acid, namely melaminium maleate monohydrate have been carried out by quantum chemical methods in addition to FTIR, FT-Raman and far-infrared spectral studies. The quantum chemical studies were performed with DFT (B3LYP) method using 6-31G(**), cc-pVDZ and 6-311++G(**) basis sets to determine the energy, structural and thermodynamic parameters of melaminium maleate monohydrate. The hydrogen atom from maleic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The ability of ions to form spontaneous three-dimensional structure through weak OHˇˇˇO and NHˇˇˇO hydrogen bonds shows notable vibrational effects. PMID:23416913

Arjunan, V; Kalaivani, M; Marchewka, M K; Mohan, S

2013-01-24

314

Study of structure-activity relationship of enantiomeric, protonated and deprotonated forms of warfarin via vibrational spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

The structure-activity relationship of the anticoagulant drug warfarin were studied by studying two enantiomeric forms (S-form and R-form) of warfarin and its protonated as well as deprotonated structures in aqueous media using density functional theory (DFT). Theoretically computed Raman and IR spectra of all the computed structures were compared and their specific vibrational spectroscopic signatures were discussed. The percentage contributions of individual normal modes of warfarin, which provides direct evidence of the different molecular activity due to change in relative atomic position of atoms in molecule, were investigated through potential energy distribution (PED). The optimized energy and molecular electrostatic potential (MEP) maps show that the S-form of the drug molecules warfarin is energetically more stable than R-form and provides higher docking opportunity for the molecular binding with the receptors in the bio-systems.

Mishra, Alok; Srivastava, Sunil Kumar; Swati, D.

2013-09-01

315

Harmonic engine  

DOEpatents

A high efficiency harmonic engine based on a resonantly reciprocating piston expander that extracts work from heat and pressurizes working fluid in a reciprocating piston compressor. The engine preferably includes harmonic oscillator valves capable of oscillating at a resonant frequency for controlling the flow of working fluid into and out of the expander, and also preferably includes a shunt line connecting an expansion chamber of the expander to a buffer chamber of the expander for minimizing pressure variations in the fluidic circuit of the engine. The engine is especially designed to operate with very high temperature input to the expander and very low temperature input to the compressor, to produce very high thermal conversion efficiency.

Bennett, Charles L. (Livermore, CA)

2009-10-20

316

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

NASA Astrophysics Data System (ADS)

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.

Srivastava, Santosh K.; Singh, Vipin B.

2013-11-01

317

DFT computation and experimental analysis of vibrational and electronic spectra of phenoxy acetic acid herbicides.  

PubMed

An absolute vibrational analysis has been attempted on the basis of experimental FTIR and NIR-FT Raman spectra with calculated vibrational wavenumbers and intensities of phenoxy acetic acids. The equilibrium geometry, bonding features and harmonic vibrational wavenumbers have been calculated with the help of B3LYP method with Dunning correlation consistent basis set aug-cc-pVTZ. The electronic structures of molecular fragments were described in terms of natural bond orbital analysis, which shows intermolecular O-HˇˇˇO and intramolecular C-HˇˇˇO hydrogen bonds. The electronic absorption spectra with different solvents have been investigated in combination with time-dependent density functional theory calculation. The pKa values of phenoxy acetic acids were compared. PMID:23466319

Arul Dhas, D; Hubert Joe, I; Roy, S D D; Balachandran, S

2013-02-09

318

DFT computation and experimental analysis of vibrational and electronic spectra of phenoxy acetic acid herbicides  

NASA Astrophysics Data System (ADS)

An absolute vibrational analysis has been attempted on the basis of experimental FTIR and NIR-FT Raman spectra with calculated vibrational wavenumbers and intensities of phenoxy acetic acids. The equilibrium geometry, bonding features and harmonic vibrational wavenumbers have been calculated with the help of B3LYP method with Dunning correlation consistent basis set aug-cc-pVTZ. The electronic structures of molecular fragments were described in terms of natural bond orbital analysis, which shows intermolecular Osbnd H⋯O and intramolecular Csbnd H⋯O hydrogen bonds. The electronic absorption spectra with different solvents have been investigated in combination with time-dependent density functional theory calculation. The pKa values of phenoxy acetic acids were compared.

Arul Dhas, D.; Hubert Joe, I.; Roy, S. D. D.; Balachandran, S.

2013-05-01

319

FTIR, Raman spectra and ab initio calculations of 2-mercaptobenzothiazole  

Microsoft Academic Search

FTIR and Raman spectra of a rubber vulcanization accelerator, 2-mercaptobenzothiazole (MBT), were recorded in the solid phase. The harmonic vibrational wavenumbers, for both the toutomeric forms of MBT, as well as for its dimeric complex, have been calculated, using ab initio RHF and density functional B3LYP methods invoking different basis sets upto RHF\\/6-31G** and B3LYP\\/6-31G** and the results were compared

Amareshwar K. Rai; Rachana Singh; K. N. Singh; V. B. Singh

2006-01-01

320

Electrodynamic vibrators  

Microsoft Academic Search

The present work describes current electrodynamic vibrators and vibration rigs for investigating materials, structural elements, machine parts, and certain biological objects subjected to vibrations and large accelerations. Methods of increasing the thrusting force and amplitude of oscillations in electrodynamic vibrators are discussed along with broadening of the frequency range. The characteristics of commercial vibrators are examined. Ways of preventing vibrations

M. D. Genkin; A. M. Rusakov; V. V. Iablonskii

1975-01-01

321

Calculation of reduced partial cross sections of molecules photodesorbing from a cold crystal surface with internal vibrations: Inclusion of curve-crossing effects  

NASA Astrophysics Data System (ADS)

A Gaussian wave packet/path integral (GWD/PI) method is used to compute final internal state distributions for a molecule photodesorbing from the surface of a zero-temperature crystal with internal vibrations in the situation where nonadiabatic coupling between two excited state potential surfaces is significant. The internal state distributions of the desorbed molecule are influenced by vast numbers of internal vibrational state transitions in the crystal which are not resolved in the calculation (or in experiment). A correlation function technique, introduced previously for the case of direct photodissociation on a single excited potential surface, is generalized to systems where two or more excited potential surfaces are nonadiabatically coupled. The accuracy of the method is successfully tested on a two-dimensional model for which numerically exact results can be computed. The method is then applied to a collinear model of a diatomic molecule photodesorbing from a chain of atoms coupled by Hooke's law springs. While exact results cannot be obtained in this case, sum rule checks suggest that the results of the GWD/PI are of acceptable accuracy (fractional error of several percent). It is found that for the class of problems under study, which feature nonadiabatic coupling that decays to zero along the photodesorption coordinate, only a few paths through the electronic state space have significant weight. This suggests that the method can be utilized to treat more complicated problems.

Cárdenas, A. E.; Coalson, R. D.

1999-06-01

322

DFT study of structure and vibrational spectra of ceramide 3: comparison to experimental data  

Microsoft Academic Search

The Fourier transform Raman and infrared (IR) spectra of the Ceramide 3 (CER3) have been recorded in the regions 200–3500 cm and 680–4000 cm, respectively. We have calculated the equilibrium geometry, harmonic vibrational wavenumbers, electrostatic potential surfaces, absolute Raman scattering activities and IR absorption intensities by the density functional theory with B3LYP functionals having extended basis set 6-311G. This work is undertaken

Soni Mishra; Poonam Tandon

2012-01-01

323

The vibrational progressions of the N-->V electronic transition of ethylene: A test case for the computation of Franck-Condon factors of highly flexible photoexcited molecules  

NASA Astrophysics Data System (ADS)

The vibrational progressions of the N-->V electronic transition of ethylene-a test case for the computation of Franck-Condon factors between electronic states exhibiting very different equilibrium geometries-have been calculated by using both the Cartesian and the curvilinear internal coordinate representations of the normal modes of vibration. The comparison of the theoretical spectra with the experimental one shows that the Cartesian representation yields vibrational progressions which are not observed in the experimental spectrum, whereas the curvilinear one gives a very satisfying agreement, even in harmonic approximation.

Borrelli, Raffaele; Peluso, Andrea

2006-11-01

324

Nonlinear vibrational resonance  

NASA Astrophysics Data System (ADS)

We examine the nonlinear response of a bistable system driven by a high-frequency force to a low-frequency weak field. It is shown that the rapidly varying temporal oscillation breaks the spatial symmetry of the centrosymmetric potential. This gives rise to a finite nonzero response at the second harmonic of the low-frequency field, which can be optimized by an appropriate choice of vibrational amplitude of the high-frequency field close to that for the linear response. The potential implications of the nonlinear vibrational resonance are analyzed.

Ghosh, Shyamolina; Ray, Deb Shankar

2013-10-01

325

Theoretical study of infrared spectra perturbed by uniform electric fields - Ab initio calculations on H2O, NH3, H2CO, and C2H4  

NASA Astrophysics Data System (ADS)

The changes in harmonic vibrational frequencies and line intensities with respect to different strengths of an applied electric field are computed using analytically calculated energy derivatives. The ground states of several small molecules are studied at the ab initio restricted Hartree-Fock self-consistent-field level with a double zeta plus polarization basis set. The dependence of vibrational frequencies and line intensities upon the applied field strength is discussed.

Andres, Jose L.; Marti, Josep; Duran, M.; Lledos, Agusti; Bertran, Juan

1991-09-01

326

Tautomeric stability, vibrational, electronic, NBO, and NMR analyses of N-[acetylamino-(3-nitrophenyl)methyl]-acetamide (ANPMA) by ab initio HF and DFT calculations  

NASA Astrophysics Data System (ADS)

This study represents an integrated approach towards understanding the vibrational, electronic, NMR, reactivity and structural aspects of N-[acetylamino-(3-nitrophenyl)methyl]-acetamide (ANPMA). Theoretical calculations were performed by ab initio HF and density functional theory (DFT)/B3LYP method using 6-311++G(d,p) basis sets. Tautomerism and the effect of solvent on the tautomeric equilibria in the gas phase and in different solvents were studied. Electronic transitions were also studied and the most prominent transition corresponds to ? ? ?\\midast. ANPMA exhibited good nonlinear optical activity and 10 times greater than that of urea. Molecular electrostatic potential (MEP) results predicted that the amide group of ANPMA to be the most reactive site for both electrophilic and nucleophilic attack.

Sridevi, C.; Panneer Selvam, N.; Shanthi, G.; Velraj, G.

2012-12-01

327

Conformational stability, structural parameters and vibrational assignment from variable temperature infrared spectra of krypton solutions and ab initio calculations of ethylisothiocyanate.  

PubMed

Variable temperature (-105 to -150 degrees C) studies of the infrared spectra (3500-400 cm(-1)) of ethylisothiocyanate, CH(3)CH(2)NCS, dissolved in liquid krypton have been recorded. Additionally the infrared spectra of the gas and solid have been re-investigated. These spectroscopic data indicate a single conformer in all physical states with a large number of molecules in the gas phase at ambient temperature in excited states of the CN torsional mode which has a very low barrier to conformational interchange. To aid in the analyses of the vibrational and rotational spectra, ab initio calculations have been carried out by the perturbation method to the second order (MP2) with valence and core electron correlation using a variety of basis sets up to 6-311+G(2df,2pd). With the smaller basis sets up to 6-311+G(d,p) and cc-PVDZ, the cis conformer is indicated as a transition state with all larger basis sets the cis conformer is the only stable form. The predicted energy difference from these calculations between the cis form and the higher energy trans conformer is about 125 cm(-1) which represents essentially the barrier to internal rotation of the NCS group (rotation around NC axis). Density functional theory calculation by the B3LYP method with the same basis sets predicts this barrier to be about 25 cm(-1). By utilizing the previously reported microwave rotational constants with the structural parameters predicted by the ab initio MP2(full)/6-311+G(d,p) calculations, adjusted r(0) structural parameters have been obtained for the cis form. The determined heavy atom parameters are: r(NC)=1.196(5), r(CS)=1.579(5), r(CN)=1.439(5), r(CC)=1.519(5)A for the distances and angles of angleCCN=112.1(5), angleCNC=146.2(5), angleNCS=174.0(5) degrees . The centrifugal distortion constants, dipole moments, conformational stability, vibrational frequencies, infrared intensities and Raman activities have been predicted from ab initio calculations and compared to experimental quantities when available. These results are compared to the corresponding quantities of some similar molecules. PMID:17433767

Durig, James R; Zheng, Chao

2007-01-09

328

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)

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.

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

2011-09-01

329

Vibrations of Orb Weaver Spider Webs  

Microsoft Academic Search

Orb weaver spiders surely use web vibrations as an information source but little is know of the subject. In order to discover what information is available, the vibrational modes of a web must be calculated. Modeling the web as a spiral on symmetric rays, vibrations will be computer-calculated and displayed. The computer-generated vibrations are compared with measurements made on a

John A. Cramer

2001-01-01

330

Ab initio calculation of 1H, 17O, 27Al and 29Si NMR parameters, vibrational frequencies and bonding energetics in hydrous silica and Na-aluminosilicate glasses  

NASA Astrophysics Data System (ADS)

Ab initio, molecular orbital (MO) calculations were performed on model systems of SiO 2, NaAlSi 3O 8 (albite), H 2O-SiO 2 and H 2O-NaAlSi 3O 8 glasses. Model nuclear magnetic resonance (NMR) isotropic chemical shifts (? iso) for 1H, 17O, 27Al and 29Si are consistent with experimental data for the SiO 2, NaAlSi 3O 8, H 2O-SiO 2 systems where structural interpretations of the NMR peak assignments are accepted. For H 2O-NaSi 3AlO 8 glass, controversy has surrounded the interpretation of NMR and infrared (IR) spectra. Calculated ? iso1H, ? iso17O, ? iso27Al and ? iso29Si are consistent with the interpretation of Kohn et al. (1992) that Si-(OH)-Al linkages are responsible for the observed peaks in hydrous Na-aluminosilicate glasses. In addition, a theoretical vibrational frequency associated with the Kohn et al. (1992) model agrees well with the observed shoulder near 900 cm -1 in the IR and Raman spectra of hydrous albite glasses. MO calculations suggest that breaking this Si-(OH)-Al linkage requires ˜+56 to +82 kJ/mol which is comparable to the activation energies for viscous flow in hydrous aluminosilicate melts.

Kubicki, J. D.; Sykes, D. G.

2004-10-01

331

Experimental and theoretical study of the vibrational spectra of 12-thiacrown-4 and 18-thiacrown-6, evaluation of the performance of the different anharmonic force fields compared to the scaled quantum mechanical force fields.  

PubMed

We report, to the best of our knowledge, for the first time the vibrational, IR and Raman, spectra of 12-thiacrown-4 (12t4) and 18-thiacrown-6 (18t6). To predict in what conformation 12t4 and 18t6 exist, for the vibrational analysis of both molecules and to assess the performance of the different computational methods for the accurate prediction of the vibrational frequencies of relatively large molecules, the computations were done using the harmonic and anharmonic force fields using the 6-31G* and 6-311G** basis sets. The computations were performed at the HF, B3LYP, CAM-B3LYP, BLYP, BP86, G96LYP, PBE1PBE, TPSSH and MP2 levels. Comparison was made between the calculated and experimental vibrational frequencies as indicated by the root-mean-square (rms) deviations, using either the unscaled and scaled harmonic vibrational frequencies and, unscaled, anharmonic vibrational frequencies. For the harmonic vibrational frequencies two scaling schemes were used. One uses one-scale-factor (1SF) scaling and the other uses 8SF scaling. In terms of the vibrational analysis of 12t4 and 18t6, the report confirms the solid state X-ray structure of D4 of 12t4 and C2 of 18t6. It is concluded that a lower rms deviation is obtained using 1SF scaled harmonic vibrational frequencies at even the HF/6-31G* level than using anharmonic vibrational frequencies at the MP2/6-311G** level. The CAM-B3LYP method showed some improvement over the traditional B3LYP method. PMID:23978743

Al-Jallal, Nada A; Al-Badri, Nada I; El-Azhary, Adel A

2013-08-08

332

Method and apparatus for vibrating a substrate during material formation  

DOEpatents

A method and apparatus for affecting the properties of a material include vibrating the material during its formation (i.e., "surface sifting"). The method includes the steps of providing a material formation device and applying a plurality of vibrations to the material during formation, which vibrations are oscillations having dissimilar, non-harmonic frequencies and at least two different directions. The apparatus includes a plurality of vibration sources that impart vibrations to the material.

Bailey, Jeffrey A. (Richland, WA); Roger, Johnson N. (Richland, WA); John, Munley T. (Benton City, WA); Walter, Park R. (Benton City, WA)

2008-10-21

333

Estimation of formamide harmonic and anharmonic modes in the Kohn-Sham limit using the polarization consistent basis sets.  

PubMed

Formamide harmonic and anharmonic frequencies of fundamental vibrations in the gas phase and in several solvents were successfully estimated in the B3LYP Kohn-Sham complete basis set limit (KS CBS). CBS results were obtained by extrapolating a power function (two-parameter formula) to the results calculated with polarization-consistent basis sets. Anharmonic corrections using the second order perturbation treatment (PT2) and hybrid B3LYP functional combined with polarization consistent pc-n (n=0, 1, 2, 3, 4) and several Pople's basis sets were analyzed for all fundamental formamide vibrational modes in the gas phase and solution. Solvent effects were modeled within a PCM method. The anharmonic frequency of diagnostic amide vibration C=O in the gas phase and the CCl(4) solution calculated with the VPT2 method was significantly closer to experimental data than the corresponding harmonic frequency. Both harmonic and anharmonic frequencies of C=O stretching mode decreased linearly with solvent polarity, expressed by relative environment permittivity (?) ratio (?-1)/(2?+1). However, an unphysical behavior of solvent dependence of some low frequency anharmonic amide modes of formamide (e.g., CN stretch, NH(2) scissoring, and NH(2) in plane bend) was observed, probably due to the presence of severe anharmonicity and Fermi resonance. PMID:21267754

Buczek, Aneta; Kupka, Teobald; Broda, Ma?gorzata A

2011-01-26

334

Vibrationally Excited C6H  

NASA Astrophysics Data System (ADS)

Rotational spectra of the linear carbon chain radical C6H in two low-lying excited vibrational states were observed both at millimeter wavelengths in a low-pressure glow discharge and at centimeter wavelengths in a supersonic molecular beam. Two series of harmonically related lines with rotational constants within 0.3% of the 2? ground state were assigned to the 2? and 2? vibronic components of an excited bending vibrational level. Measurements of the intensities of the lines in the glow discharge indicate that the 2? component lies very close to ground, but the 2? component is much higher in energy. The standard Hamiltonian for an isolated 2? state with five spectroscopic constants reproduces the observed rotational spectrum, but several high-order distortion terms in the spin-rotation interaction are needed to reproduce the spectrum of the 2? component in C6H and C6D. The derived spectroscopic constants allow astronomers to calculate the rotational spectra of the 2? and 2? states up to 260 GHz to within 0.1 km s-1 or better in equivalent radial velocity.

Gottlieb, C. A.; McCarthy, M. C.; Thaddeus, P.

2010-08-01

335

Theoretical studies of high-harmonic generation based on the Keldysh Faisal Reiss theory  

NASA Astrophysics Data System (ADS)

We use the Keldysh-Faisal-Reiss (KFR) approach to study the process of high-harmonic generation (HHG) for hydrogen and helium atoms and a hydrogen molecule where the helium atom and hydrogen molecule wavefunctions are described by a 1s single Slater determinant. In this model we directly use the photoionization amplitude calculated by the KFR approach and relate it to the HHG spectra. We plot HHG from hydrogen and helium atoms, and a hydrogen molecule in the presence of a linearly and circularly polarized laser field, and also discuss the nuclear motion corrections for the hydrogen molecule, which are calculated under the Frank-Condon (FC) approximation by using both displaced-distorted harmonic oscillators and Morse wavefunctions. Contributions from each vibrational state are also discussed.

Mineo, H.; Nagaya, K.; Hayashi, M.; Lin, S. H.

2007-06-01

336

Finite amplitude gravity waves - Harmonics, advective steepening and saturation  

Microsoft Academic Search

A new approach is used to calculate steepening, harmonics generation, and saturation of a finite amplitude gravity wave, with attention confined to a single wave or wave packet in a quasi-stationary background. The calculation indicates that harmonics are generated which cause the wave velocity fluctuation to steepen; harmonics of the density fluctuation are neglected. The wave velocity gradually steepens until

J. Weinstock

1986-01-01

337

Towards an understanding of the vibrational spectrum of the neutral Au7 cluster.  

PubMed

We present a detailed theoretical study of the vibrational spectrum of the neutral Au(7) cluster, aimed at understanding its reported experimental spectrum [P. Gruene et al., Science, 2008, 321, 674]. We study the effect of vibrational anharmonicity, polymorphism, noble gas embedding, and the use of various electronic-structure methods. We use a vibrational configuration-interaction approach (VCI) with a vibrational self-consistent field (VSCF) basis, in order to study the effect of vibrational anharmonicity for the density functional theory (DFT) global minimum energy structure. Our implementation of the VSCF/VCI method is based on the direct calculation of the potential energy surface (PES) using pseudo potential plane-wave DFT. An efficient reduction of the number of mode-mode couplings between vibrational modes (fast-VSCF/VCI) is used to speed up calculations. We show that the rather small anharmonicity does not account for the difference between harmonic and experimental frequencies and consequently for the large global scaling factor, reported by the authors of the experiment. Instead, the use of different electronic structure methods allows for a significant reduction of the scaling factor. We also show that krypton embedding does not significantly change the vibrational frequencies of the Au(7) cluster. PMID:23258549

Mancera, Luis A; Benoit, David M

2012-12-20

338

Magnetostriction and Motor Vibration  

NASA Astrophysics Data System (ADS)

These days, a quiet induction motor is strongly demanded. Electromagnetic factor is main cause of vibration and acoustic noise of small induction motor. Electromagnetic forces and magnetostrictive forces are considered of origin of electromagnetic vibration and noise. In this paper, magnetostrictive vibration of ring of electrical steel sheets was simulated by mechanical Finite Element Method. Magnetostriction was assumed as external forces and they were added at each node of meshed ring. Resonant frequency and mode of ring were calculated. In steel sheet ring excited by PWM voltage source inverter, frequency spectrum of vibration of ring was measured and compared with calculated results. It was confirmed that these procedure simulated magnetostriction behavior of electrical steel sheets. Furthermore, electromagnetic forces of small induction motor was calculated and compared with magnetostriction data. It became clear that electromagnetic vibration was affected by the magnetostriction of steel. These results will be useful to reduce the acoustic noise and to develop quiet motors.

Ishibashi, Fuminori; Noda, Shinichi; Yanase, Shunji; Sasaki, Tadashi

339

Vibrational spectra, structure, and theoretical calculations of 2-chloro- and 3-chloropyridine and 2-bromo- and 3-bromopyridine  

NASA Astrophysics Data System (ADS)

The infrared and Raman spectra of 2-chloropyridine, 3-chloropyridine, 2-bromopyridine, and 3-bromopyridine have been recorded and assigned. Density functional theory calculations (B3LYP with 6-311++G(d,p) basis set) produce excellent agreement with the experimental values. Ab initio calculations (MP2 with the cc-pVTZ basis set) were utilized to compute the molecular structures, which were compared to those of pyridine and the corresponding fluoropyridines. All of the 2-halopyridines show a shortening of the N-C(2) bond resulting from the halogen substitution on the C(2) carbon atom. All of the other ring bond distances for the 2-halopyridines and 3-halopyridines are little different from pyridine itself.

Boopalachandran, Praveenkumar; Sheu, Hong-Li; Laane, Jaan

2012-09-01

340

The combined use of SCF-MO calculations and experimental data in the evaluation of quadratic force fields MOCIC potential functions for fluoroform, methyl acetylene, and methyl cyanide  

Microsoft Academic Search

A semiempirical method combining SCF-MO calculations and limited vibrational data has been employed to evaluate the completely general quadratic potential fields of fluoroform, methyl acetylene, and acetonitrile. MOCIC (molecular orbital constraint using interaction coordinates) potential fields are presented for gas phase molecules of intermediate size. Here general harmonic force fields or excellent approximations utilizing extensive experimental data are available as

B. I. Swanson; T. H. Arnold; Y. Yamaguchi

1979-01-01

341

CALCULATIONS ON VIBRATIONAL PROPERTIES OF H-BONDED OH GROUPS, AS A FUNCTION OF H-BOND GEOMETRY  

Microsoft Academic Search

Ab initio calculations on (H,O), have been performed on 10 model geometries and 17 geometrieswhichshnulateG-H. . a0 contacts encountered in the crystals of P-D-fructose, p-D-srabinose and turanose. The variations with geometry of the hydrogen-bond energy AE, the lengthening of the donor OH distance (Ar), the frequency shift AUOH and the IR absorption intensity Z are investigated. The relation between AVOH

J. G. C. M. VAN DUIJNEVELDT-VAN; F. B. VAN DUIJNEVELDT; D. R. WILLIAMS

342

Some Aspects of the Harmonic Analysis of Irregularly Spaced Data.  

National Technical Information Service (NTIS)

An investigation into the effect of irregular spacing of data upon harmonic coefficients is presented. The statistical model for the irregularity of the spacing is subject to certain constraints. The coefficients of each harmonic are calculated individual...

E. P. Avara M. Kays

1970-01-01

343

Harmonic and power factor compensation using WRIM based on sliding mode controller  

Microsoft Academic Search

This paper proposes an APF (active power filter) with WRIM (wound rounded induction motor) controlled by sliding mode which can compensate harmonic currents generated in a power system. As nonlinear loads increase gradually in industry fields, harmonic current generated in the electric power network system also increases. Harmonic current makes a power network current distorted and generates heat, vibration and

Seung-Mo Kim; Kyoung-Soo Park; Yoon-Ho Kim

2003-01-01

344

Optimized Structure and Vibrational Properties by Error Affected Potential Energy Surfaces  

PubMed Central

The precise theoretical determination of the geometrical parameters of molecules at the minima of their potential energy surface and of the corresponding vibrational properties are of fundamental importance for the interpretation of vibrational spectroscopy experiments. Quantum Monte Carlo techniques are correlated electronic structure methods promising for large molecules, which are intrinsically affected by stochastic errors on both energy and force calculations, making the mentioned calculations more challenging with respect to other more traditional quantum chemistry tools. To circumvent this drawback in the present work, we formulate the general problem of evaluating the molecular equilibrium structures, the harmonic frequencies, and the anharmonic coefficients of an error affected potential energy surface. The proposed approach, based on a multidimensional fitting procedure, is illustrated together with a critical evaluation of systematic and statistical errors. We observe that the use of forces instead of energies in the fitting procedure reduces the statistical uncertainty of the vibrational parameters by 1 order of magnitude. Preliminary results based on variational Monte Carlo calculations on the water molecule demonstrate the possibility to evaluate geometrical parameters and harmonic and anharmonic coefficients at this level of theory with an affordable computational cost and a small stochastic uncertainty (<0.07% for geometries and <0.7% for vibrational properties).

Zen, Andrea; Zhelyazov, Delyan; Guidoni, Leonardo

2013-01-01

345

Melting of ?-Al2O3 and vitrification of the undercooled alumina liquid: Ab initio vibrational calculations and their thermodynamic implications  

NASA Astrophysics Data System (ADS)

We present the results of a computational investigation of the structure-energy and vibrational properties of alumina under various aggregation states (crystalline, glassy, and liquid) with ab initio procedures. IV-fold, V-fold, and VI-fold oxygen-coordinated aluminum monomeric forms in a dielectric continuum with dielectric constant ? = 4.575 were investigated through DFT/B3LYP gas-phase calculations coupled with a Polarized Continuum Model approach and those of the periodical structure D63d (R-3c) which leads to the ?-Al2O3 polymorph of alumina, when subjected to symmetry operations, were investigated with the same functional within the LCAO approximation and in the framework of Bloch's theorem. Based on the computed energies and vibrational features, an aggregate of the D63d positively charged cluster [Al12O11]14+ contoured by [AlO4]5- units in an approximate 1:3 proportion to achieve neutrality satisfactorily reproduce the heat capacity of the liquid within experimental uncertainty. The glass is seen as a wrong accretionary form induced by fast cooling rates and subjected to steric forces that locally modify the coordination state of the central atom. Cessation of rotational and translational movements, only partly counterbalanced by acoustic sine-wave-dispersed and excess phonons, gives rise to the huge heat-capacity gap observed at the glass transition (~5.3R). When cooling rates are sufficiently slow, the accretion around the D63d seeds follows the structural constraints and the heat capacity of ?-alumina is almost perfectly reproduced by the 27 Einstein oscillators coupled with the 3 acoustic terms and the anharmonic corrections.

Belmonte, D.; Ottonello, G.; Zuccolini, M. Vetuschi

2013-02-01

346

Structural, vibrational, electronic, NMR and reactivity analyses of 2-amino-4H-chromene-3-carbonitrile (ACC) by ab initio HF and DFT calculations.  

PubMed

This study represents an integrated approach towards understanding the vibrational, electronic, NMR, reactivity and structural aspects of 2-amino-4H-chromene-3-carbonitrile (ACC). A detailed interpretation of the FT IR, UV and NMR spectra were reported. Theoretical calculations were performed by ab initio HF and density functional theory (DFT)/B3LYP method using 6-311++G(d,p) basis sets. The electronic properties was also studied and the most prominent transition corresponds to ???*. The lower frontier orbital energy gap and high dipole moment illustrates the high reactivity of the title molecule. The NMR results indicated that the observed chemical shifts depend not only on the structure of the molecule being studied, but also on the solvent used. ACC exhibited good nonlinear optical activity and was much greater than that of urea. Molecular electrostatic potential (MEP) results predicted that the enaminonitrile fragment of ACC to be the most reactive site for both electrophilic and nucleophilic attack. In addition, the thermodynamic properties of the compound were calculated at different temperatures and corresponding relations between the properties and temperature were also studied. PMID:22248456

Sridevi, C; Shanthi, G; Velraj, G

2011-12-29

347

Structural, vibrational, electronic, NMR and reactivity analyses of 2-amino-4H-chromene-3-carbonitrile (ACC) by ab initio HF and DFT calculations  

NASA Astrophysics Data System (ADS)

This study represents an integrated approach towards understanding the vibrational, electronic, NMR, reactivity and structural aspects of 2-amino-4H-chromene-3-carbonitrile (ACC). A detailed interpretation of the FT IR, UV and NMR spectra were reported. Theoretical calculations were performed by ab initio HF and density functional theory (DFT)/B3LYP method using 6-311 + +G(d,p) basis sets. The electronic properties was also studied and the most prominent transition corresponds to ? ? ?*. The lower frontier orbital energy gap and high dipole moment illustrates the high reactivity of the title molecule. The NMR results indicated that the observed chemical shifts depend not only on the structure of the molecule being studied, but also on the solvent used. ACC exhibited good nonlinear optical activity and was much greater than that of urea. Molecular electrostatic potential (MEP) results predicted that the enaminonitrile fragment of ACC to be the most reactive site for both electrophilic and nucleophilic attack. In addition, the thermodynamic properties of the compound were calculated at different temperatures and corresponding relations between the properties and temperature were also studied.

Sridevi, C.; Shanthi, G.; Velraj, G.

2012-04-01

348

Ab initio calculation of band absolute intensities in IR spectra  

NASA Astrophysics Data System (ADS)

Ab initio calculations in a harmonic approximation of absorption band absolute intensities in infrared spectra were carried out for 3 hydrocarbons and 14 halogenated hydrocarbons. The calculated data were compared with experimental values of the absolute absorption intensities. It is shown that a Hartree-Fock calculation method overestimates significantly (by an average of 66%) the integrated absolute intensities of the fundamental bands in the region 575-4000 cm-1. The deviation is reduced to 32% in the case of the MP2 method of accounting for electron correlations. Most of the overestimation occurs for bands corresponding to vibrations involving halogen atoms.

Pavlyuchko, A. I.; Vasilyev, E. V.; Gribov, L. A.

2012-01-01

349

Covariant Harmonic Oscillators and Coupled Harmonic Oscillators.  

National Technical Information Service (NTIS)

It is shown that the system of two coupled harmonic oscillators shares the basic symmetry properties with the covariant harmonic oscillator formalism which provides a concise description of the basic features of relativistic hadronic features observed in ...

D. Han Y. S. Kim M. E. Noz

1995-01-01

350

2D full field vibration analysis with multiplexed digital holograms  

Microsoft Academic Search

Opportunities for full field 2D amplitude and phase vibration analysis are presented. It is demonstrated that it is possible to simultaneously encode-decode 2D the amplitude and phase of harmonic mechanical vibrations. The process allows the determination of in plane and out of plane vibration components when the object is under a pure sinusoidal excitation. The principle is based on spatial

Pascal Picart; Julien Leval; Jean Claude Pascal; Jean Pierre Boileau; Michel Grill; Jean Marc Breteau; Benjamin Gautier; Stéphane Gillet

2005-01-01

351

Anharmonic vibrations of an ''ideal'' Hooke's law oscillator  

Microsoft Academic Search

The vibrations of a mass connected to fixed supports by two ''ideal'' Hooke's law springs are considered. Although the longitudinal vibrations of this system are always harmonic, the transverse vibrations are, in general, anharmonic even though both springs obey Hooke's law. In fact, it is found that as the supports are brought together, allowing the springs to become slack, the

John Thomchick; J. P. McKelvey

1978-01-01

352

Semiclassical theory of plate vibrations.  

National Technical Information Service (NTIS)

The bi-harmonic equation of flexural vibrations of elastic plates is studied by a semiclassical method which can easily be generalized for other models of wave propagation. The surface and perimeter terms of the asymptotic number of levels are derived exa...

E. Bogomolny E. Hugues

1996-01-01

353

Vibrational spectroscopy of maleimide  

NASA Astrophysics Data System (ADS)

Vibrational spectroscopy represents an important analysis tool for the characterization of different molecular systems. In the present work a model compound, maleimide, has been characterized by means of inelastic neutron scattering measurements and theoretical calculations.

Corsaro, C.; Parker, S. F.

2004-07-01

354

Infrared and Raman Spectra, Conformational Stability, Barriers to Internal Rotation, Vibrational Assignment, and AB Initio Calculations for Some Substituted Halo-Propenes  

NASA Astrophysics Data System (ADS)

The infrared (3200 to 50 cm^{ -1}) and Raman (3200 to 10 cm^ {-1}) spectra of gaseous and solid trans -1,3-dichloropropene, 2-butenoyl chloride, trans-1-chloro -2-butene, cis-1,3-dichloropropene and trans-1-bromo-2-butene have been recorded. Additionally, the Raman spectra of the liquid phases of these molecules have been obtained and qualitative depolarization ratios have been measured for trans-1,3-dichloropene. The fundamental asymmetric torsion for the more stable gauche conformer has been observed in the far infrared spectra of the gaseous phase of trans -1,3-dichloropropene, trans-1-chloro-2-butene and trans -1-bromo-2-butene. The corresponding mode for the less stable syn conformer has also been observed for trans-1 -chloro-2-butene and trans-1,3-dichloropropene. The asymmetric torsional fundamental of the more stable s-trans and the higher energy s-cis (syn) form of 2-butenoyl chloride have been observed at 97.5 and 86.9 cm^{ -1}, respectively. From these data the asymmetric potential functions governing internal rotation about the C-C bond has been determined and the corresponding potential coefficients have been determined. The enthalpy difference between the conformers of trans-1,3-dichloropropene and 2-butenoyl chloride have been determined to be 342 +/- 36 cm^{-1} and 105 +/- 152 cm^ {-1}, respectively, from variable temperature studies of the Raman or infrared spectra. The fundamental asymmetric torsional mode arising from the gauche form of cis-1,3-dichloropropene was not observed in the far infrared spectrum of the gas and, therefore, precludes an experimental determination of the potential function. A complete assignment of the vibrational fundamentals has been proposed for all of these molecules based on ab initio calculated frequencies and by comparison with the vibrational spectra of some similar molecules. All of these data are compared to the corresponding quantities obtained from ab initio Hartree-Fock gradient calculations employing either the RHF/STO-3G^*, RHF/3-21G^*, RHF/6-31G^* or the MP2/6-31G^* basis sets. Additionally, complete equilibrium geometries have been determined for all possible rotamers of these molecules. The results are discussed and compared with the corresponding quantities obtained for some similar molecules.

Costner, Timothy Glenn

355

Nonlinear cyclotron harmonic absorption  

SciTech Connect

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.

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

356

Sunspots and their simple harmonic motion  

NASA Astrophysics Data System (ADS)

In this paper an example of a simple harmonic motion, the apparent motion of sunspots due to the Sun’s rotation, is described, which can be used to teach this subject to high-school students. Using real images of the Sun, students can calculate the star’s rotation period with the simple harmonic motion mathematical expression.

Ribeiro, C. I.

2013-09-01

357

Mutual impedance of half-wavelength vibrator and a passive vibrator of arbitrary length  

Microsoft Academic Search

The mutual impedances between the half-wavelength active and the loaded passive vibrators of a multirange vibrator antenna are calculated on the basis of a current distribution along a passive vibrator which is more complicated than the usual sinusoidal one. Numerical calculations show the strong effect of loading of the vibrators on mutual impedance. Bounds on the applicability of the sinusoidal

I. A. Bolsunov; E. A. Steriopolo

1977-01-01

358

Measurement and analysis of the infrared absorption spectrum of the radical cation of [34](1, 2, 4, 5)cyclophane: Observation of electron-molecular vibration interaction between two benzene moieties  

NASA Astrophysics Data System (ADS)

A high-quality infrared absorption spectrum has been observed for the radical cation of [34](1, 2, 4, 5)cyclophane in a dichloromethane solution by using a Fourier-transform infrared spectrometer contained in an inert gas glovebox system. The structures and vibrational properties (harmonic frequencies, vibrational modes, and infrared intensities) have been calculated for the neutral species and radical cation of [34](1, 2, 4, 5)cyclophane by density functional theory at the B3LYP/6-311+G(d,p) level. The observed infrared spectra of the neutral species and radical cation are in good agreement with those calculated. Some specific vibrational modes of the radical cation have large infrared absorption intensities. The origin of the large infrared absorption intensities characteristic of the radical cation is discussed in terms of electron-molecular vibration interaction (changes in electronic structure induced by specific normal vibrations) between two benzene moieties of [34](1, 2, 4, 5)cyclophane.

Sakamoto, Akira; Tanaka, Nobuki; Shinmyozu, Teruo

2013-06-01

359

Molecular structure and vibrational spectra of 4-nitrobenzylchloride by ab initio Hartree–Fock and density functional methods  

Microsoft Academic Search

The Fourier transform Raman and Fourier transform infrared spectra 4-nitrobenzylchloride of (NBC) were recorded in the solid phase. The Fourier transform gas phase infrared spectrum of NBC was also recorded. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by HF\\/DFT (B3LYP and BLYP) and SVWN methods with the 6-31G(d,p) basis set. The scaled theoretical

N. Sundaraganesan; H. Umamaheswari; C. Meganathan; S. Sebastian

2008-01-01

360

Calcul des vibrations avec impact et frottement d'une structure tubulaire avec supports a jeux. (Computation of impact-friction interaction between a vibrating tube and its loose supports).  

National Technical Information Service (NTIS)

Maintaining PWR components in reliable operating condition requires complex design to prevent various damaging processes including flow-induced vibration and wear mechanisms. To improve prediction of tube/support interaction and wear in PWR components, ED...

G. Jacquart N. Gay

1993-01-01

361

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)

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) Ĺ, ? = 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 HˇˇˇN and possibly also Csbnd HˇˇˇO favors a dimer formation in the crystal structure. The dimers are further linked by a Nsbnd HˇˇˇO 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 HˇˇˇN hydrogen bond has also been considered. The structural and vibrational properties of the intra-molecular Nsbnd HˇˇˇO interaction are described.

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

2013-04-01

362

Reduced and exact quantum dynamics of the vibrational relaxation of a molecular system interacting with a finite-dimensional bath.  

PubMed

We investigate the vibrational relaxation of a Morse oscillator, nonlinearly coupled to a finite-dimensional bath of harmonic oscillators at zero temperature, using two different approaches: Reduced dynamics with the help of the Lindblad formalism of reduced density matrix theory in combination with Fermi's Golden Rule, and exact dynamics (within the chosen model) with the multiconfiguration time-dependent Hartree (MCTDH) method. Two different models have been constructed, the situation where the bath spectrum is exactly resonant with the anharmonic oscillator transition frequencies, and the case for which the subsystem is slightly off-resonant with the environment. At short times, reduced dynamics calculations describe the relaxation process qualitatively well but fail to reproduce recurrences observed with MCTDH for longer times. Lifetimes of all the vibrational levels of the Morse oscillator have been calculated, and both Lindblad and MCTDH results show the same dependence of the lifetimes on the initial vibrational state quantum number. A prediction, which should be generic for adsorbate systems is a striking, sharp increase of lifetimes of the subsystem vibrational levels close to the dissociation limit. This is contradictory with harmonic/linear extrapolation laws, which predict a monotonic decrease of the lifetime with initial vibrational quantum number. PMID:22775197

Bouakline, Foudhil; Lüder, Franziska; Martinazzo, Rocco; Saalfrank, Peter

2012-08-10

363

Anharmonic vibrational analysis of water at CCSD(T) level: Comparison of traditional and explicitly correlated methods  

NASA Astrophysics Data System (ADS)

Achieving the spectroscopic accuracy in ab initio calculation of harmonic vibrational frequencies and vibrational anharmonicities is challenging due to two well-understood limitations. First, accurate results require a good description of electron correlation. Second, correlated calculations require large one-electron basis sets. It is well known that the convergence of harmonic frequencies with respect to the basis set size is slow. We now report that the convergence of cubic and quartic force constants in traditional CCSD(T) calculations of H2O with Dunning's cc-pVXZ family of basis sets is also frustratingly slow. As an alternative, we explore the performance of R12/B, R12/C and F12/C explicitly correlated methods at the CCSD(T) level. We find that an excellent convergence of harmonic frequencies and cubic force constants is provided by all three explicitly correlated methods with modest R12 basis sets; larger R12 basis sets appear necessary for the accurate description of quartic force constants and vibrational anharmonicities in water.

Kahn, Kalju; Kirtman, Bernard; Noga, Jozef; Ten-no, Seiichiro

2012-12-01

364

High-harmonic transient grating spectroscopy of NO2 electronic relaxation.  

PubMed

We study theoretically and experimentally the electronic relaxation of NO(2) molecules excited by absorption of one ?400 nm pump photon. Semiclassical simulations based on trajectory surface hopping calculations are performed. They predict fast oscillations of the electronic character around the intersection of the ground and first excited diabatic states. An experiment based on high-order harmonic transient grating spectroscopy reveals dynamics occurring on the same time scale. A systematic study of the detected transient is conducted to investigate the possible influence of the pump intensity, pump wavelength, and rotational temperature of the molecules. The quantitative agreement between measured and predicted dynamics shows that, in NO(2), high harmonic transient grating spectroscopy encodes vibrational dynamics underlying the electronic relaxation. PMID:23248999

Ruf, H; Handschin, C; Ferré, A; Thiré, N; Bertrand, J B; Bonnet, L; Cireasa, R; Constant, E; Corkum, P B; Descamps, D; Fabre, B; Larregaray, P; Mével, E; Petit, S; Pons, B; Staedter, D; Wörner, H J; Villeneuve, D M; Mairesse, Y; Halvick, P; Blanchet, V

2012-12-14

365

Heat load tests of superconducting magnets vibrated electromagnetically for the Maglev train  

Microsoft Academic Search

Superconducting magnets on Maglev trains vibrate due to harmonic ripples of electromagnetic flux generated by ground coils. Heat load caused by vibration in the magnet amounted to several tens of watts in the electromagnetic vibration test. This was mainly because a.c. loss was induced in the helium vessel housing the superconducting coil, due to relative vibration between the aluminium thermal

J. Ohmori; H. Nakao; T. Yamashita; Y. Sanada; M. Shudou; M. Kawai; M. Fujita; M. Terai; A. Miura

1997-01-01

366

Vibrational (FT-IR and FT-Raman) spectra and quantum chemical studies on the molecular orbital calculations, chemical reactivity and thermodynamic parameters of 2-chloro-5-(trifluoromethyl) aniline.  

PubMed

In this work, the vibrational characteristics of 2-chloro-5-(trifluoromethyl) aniline have been investigated and both the experimental and theoretical vibrational data indicate the presence of various functional groups within the title molecule. The influence of chlorine substituent on the vibrational wavenumbers of a molecule in comparison with aniline and trifluoromethyl aniline has been discussed in detail. The density functional theoretical (DFT) computations were performed at the B3LYP/6-31++G(3df,3pd)/6-31G(3df,3pd) levels to derive the optimized geometry, vibrational wavenumbers with IR and Raman intensities. Furthermore, the molecular orbital calculations such as; natural bond orbitals (NBOs) and HOMO-LUMO energy gap and mapped molecular electrostatic potential (MEP) surfaces were also performed with the same level of DFT. The temperature dependence thermodynamic parameters of a molecule were illustrated on the basis of their correlation graphs. The detailed interpretation of the vibrational spectra has been carried out with the aid of potential energy distribution (PED) results obtained from MOLVIB program. The delocalization of electron density in various constituents of the molecule has been discussed with the aid of NBO and HOMO-LUMO energy gap analysis. PMID:23416911

Karthick, T; Balachandran, V; Perumal, S; Nataraj, A

2013-01-24

367

Vibrational (FT-IR and FT-Raman) spectra and quantum chemical studies on the molecular orbital calculations, chemical reactivity and thermodynamic parameters of 2-chloro-5-(trifluoromethyl) aniline  

NASA Astrophysics Data System (ADS)

In this work, the vibrational characteristics of 2-chloro-5-(trifluoromethyl) aniline have been investigated and both the experimental and theoretical vibrational data indicate the presence of various functional groups within the title molecule. The influence of chlorine substituent on the vibrational wavenumbers of a molecule in comparison with aniline and trifluoromethyl aniline has been discussed in detail. The density functional theoretical (DFT) computations were performed at the B3LYP/6-31++G(3df,3pd)/6-31G(3df,3pd) levels to derive the optimized geometry, vibrational wavenumbers with IR and Raman intensities. Furthermore, the molecular orbital calculations such as; natural bond orbitals (NBOs) and HOMO-LUMO energy gap and mapped molecular electrostatic potential (MEP) surfaces were also performed with the same level of DFT. The temperature dependence thermodynamic parameters of a molecule were illustrated on the basis of their correlation graphs. The detailed interpretation of the vibrational spectra has been carried out with the aid of potential energy distribution (PED) results obtained from MOLVIB program. The delocalization of electron density in various constituents of the molecule has been discussed with the aid of NBO and HOMO-LUMO energy gap analysis.

Karthick, T.; Balachandran, V.; Perumal, S.; Nataraj, A.

2013-04-01

368

State-to-state vibration-translation and vibration-vibration rate constants in H{sub 2}-H{sub 2} and HD-HD collisions  

SciTech Connect

The authors present calculations of vibration-vibration and vibration-translation energy transfer rate constants in diatom-diatom collisions. The results are compared to recent experimental measurements.

Cacciatore, M. [Universita di Bari (Italy); Billing G.D. [Univ. of Copenhagen (Denmark)

1992-01-09

369

Color harmonization for images  

NASA Astrophysics Data System (ADS)

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.

Tang, Zhen; Miao, Zhenjiang; Wan, Yanli; Wang, Zhifei

2011-04-01

370

Integration of cryogenic ion vibrational predissociation spectroscopy with a mass spectrometric interface to an electrochemical cell.  

PubMed

Cryogenic ion vibrational predissociation (CIVP) spectroscopy is used to structurally characterize electrochemically (EC)-generated oxidation products of the benchmark compound reserpine. Ionic products were isolated using EC-electrospray ionization (ESI) coupled to a 25 K ion trap prior to injection into a double-focusing, tandem time-of-flight photofragmentation mass spectrometer. Vibrational predissociation spectroscopy was carried out by photoevaporation of weakly bound N2 adducts over the range 800-3800 cm(-1) in a linear (i.e., single photon) action regime, thus enabling direct comparison of the experimental vibrational pattern with harmonic calculations. The locations of the NH and OH stretching fundamentals are most consistent with formation of 9-hydroxyreserpine, which is a different isomer than considered previously. This approach thus provides a powerful structural dimension for the analysis of electrochemical processes detected with the sensitivity of mass spectrometry. PMID:23767985

Fournier, Joseph A; Wolk, Arron B; Johnson, Mark A

2013-07-10

371

Lowest energy vibrational modes of some naphthalene derivatives: Azulene, quinoline, isoquinoline - Experiment and theory  

NASA Astrophysics Data System (ADS)

Far infrared (FIR) gas phase absorption spectra of azulene, quinoline and isoquinoline have been recorded using a Fourier transform Bruker IFS125 interferometer at medium resolution (0.5 cm?1). Assignments of these weak vibrational bands were performed using density-functional theory calculations carried out at the harmonic and anharmonic levels. Agreement between observed and calculated band positions is better than 5% for azulene and 1% for quinoline and isoquinoline. The relative band intensities are also correctly predicted. Molecular structure dependence of the FIR spectra is discussed based on the comparative study of three selected FIR modes.

Martin-Drumel, M. A.; Pirali, O.; Loquais, Y.; Falvo, C.; Bréchignac, Ph.

2013-02-01

372

Ab initio self-consistent field study of the vibrational spectra for NO sub 3 geometric isomers  

SciTech Connect

Ab initio self-consistent field results at the UHF/6-31G* and UHF-DZP levels for harmonic vibrational frequencies of symmetric NO{sub 3} with C{sub 2v}, C{sub s}, and D{sub 3h} symmetry; cis and trans forms of OONO are reported. At both levels of calculations (6-31G* and DZP), the theoretical vibrational frequencies for C{sub 2v} sym-NO{sub 3} are in agreement with the recent experimental results. Their calculations for cis and trans isomers of OONO show large deviations from the only observed vibrational frequency (1,838 cm{sup {minus}1}) for trans OONO. The trans isomer of OONO is predicted to be more stable than the cis isomer by approximately 2 kcal/mol and in each case, the ground state for OONO is predicted to be {sup 2}A{double prime}.

Morris, V.R.; Hall, J.H. Jr. (Atlanta Univ. Center, Inc., GA (USA) Georgia Institute of Technology, Atlanta (USA)); Bhatia, S.C. (Atlanta Univ. Center, Inc., GA (USA) Spelman College, Atlanta, GA (USA))

1990-09-20

373

DFT calculation of the chromyl nitrate, CrO2(NO3)2 The molecular force field.  

PubMed

We have carried out a structural and vibrational theoretical study for chromyl nitrate. The density functional theory has been used to study its structure and vibrational properties. The geometries were fully optimised at the B3LYP/Lanl2DZ, 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 chromyl nitrate are consistent with the experimental IR and Raman spectra in the solid and liquid phases. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by nitrate groups of this compound as monodentate and bidentate. We have also made the assignment of all the observed bands in the vibrational spectra for chromyl nitrate. The nature of the Cr-O and Cr<--O bonds in the compound were quantitatively investigated by means of Natural Bond Order (NBO) analysis. The topological properties of electronic charge density are analysed employing Bader's Atoms in Molecules theory (AIM). PMID:17669684

Brandán, S A; Roldán, M L; Socolsky, C; Ben Altabef, A

2007-06-23

374

Calculation of reduced partial cross sections of molecules photodesorbing from a cold crystal surface with internal vibrations: Inclusion of curve-crossing effects  

Microsoft Academic Search

A Gaussian wave packet\\/path integral (GWD\\/PI) method is used to compute final internal state distributions for a molecule photodesorbing from the surface of a zero-temperature crystal with internal vibrations in the situation where nonadiabatic coupling between two excited state potential surfaces is significant. The internal state distributions of the desorbed molecule are influenced by vast numbers of internal vibrational state

A. E. Cárdenas; R. D. Coalson

1999-01-01

375

Bisulfide complexes of zinc and cadmium in aqueous solution: Calculation of structure, stability, vibrational, and NMR spectra, and of speciation on sulfide mineral surfaces  

NASA Astrophysics Data System (ADS)

Ab initio self-consistent-field molecular orbital (SCF-MO) calculations have been employed to determine the structures and properties of Zn and Cd bisulfides and their hydrates. Calculated M-S bond lengths, R(M-S), for M( SH) n( OH2) 2- na species are consistently about 0.05 Ĺ longer than the experimental ones but show the right trends with n and a. Calculated Zn-S symmetric and average stretching frequencies scale linearly with R(Zn-S) -1, so that Zn-S distances can be estimated from vibrational spectra and vice versa. The total NMR shieldings of Zn and Cd in M( SH) 2- nn species show a shallow minimum for n= 3, and the shift compared to free M 2+ can be well fitted to a function increasing linearly with n and decreasing exponentially with R(M-S). The calculated shielding anisotropy for Cd(SH) -3 is in good agreement with observed values for the C3 h symmetry species Cd(SR) -3 in solids. Complexation of water to Zn(SH) 2 produces slightly larger Zn-S distances and smaller Zn shieldings due to the deshielding effect of the tightly bound water. For Zn(SH) -3, on the other hand, hydration is less exothermic since it requires greater Zn-S bond elongation and results in a longer Zn-O bond. Reduction of the magnitude of deshielding from S, coupled with only a small deshielding from O, causes the Zn NMR shielding of Zn(SH) 3OH -2 to be larger than that of Zn(SH) -3. Such effects of hydration on structure and shielding are much like those previously seen in studies of Zn and Cd chlorides. Comparison of the isomeric species Zn(SH) 3OH -2 and ZnS(SH) 2(OH 2) -2 shows the former to be more stable by more than 50 kJ/mol. The two species also differ spectroscopically, with ZnS(SH) 2(OH 2) -2 having a higher stretching frequency and a lower Zn NMR shielding. Equivalently, for the species Zn(SH) 3(OH 2) -, the H 2O is calculated to be more acidic than the SH -. Both H 2O and SH - are more acidic in the complexes studied herein than when occurring as the free molecules. The quantitative change is, in fact, greater for SH -, but not enough to make it more acidic than H 2O. Comparisons of the energies of intermediate members in some relevant chemical series indicate that Zn(SH) -3 is enhanced in stability compared to Zn(SH) 2 and Zn(SH) -24, and that Zn(SH) 3(OH) -2 is enhanced in stability compared to Zn(SH) -24 and Zn(OH) -24; whereas Zn(SH) 2Cl -22 is unstable energetically compared to Zn(SH) -24 and ZnCl -24. This supports the occurrence of Zn(SH) -3 and Zn(SH) 3(OH) -2 species and argues against that of Zn(SH) 2Cl -22. Zn(SH) -3 also provides a model for Zn sites on the surface of solid ZnS, showing the geometric relaxation expected compared to the bulk. Hydration of the ZnS surface can be modeled by the species Zn(SH) 3(OH 2) -1. Such Zn and Cd species have large NMR shielding anisotropies, and the Cd species may be observable using modern NMR techniques.

Tossell, J. A.; Vaughan, D. J.

1993-05-01

376

Strong intramolecular hydrogen bonds. Part I. Vibrational frequencies of the OH group in some picolinic acid N-oxides predicted from DFT calculated potentials and located in the infrared spectra  

Microsoft Academic Search

Hydrogen bonding in picolinic acid N-oxide (I), its 4-nitro (III), 4-methoxy (IV), 4-amino (V) derivatives and in quinaldic acid N-oxide (II) was characterized by calculations (B3LYP\\/6-31G(d)) of metric parameters, H-bond energies and one-dimensional proton potential functions with vibrational energy levels. Solvent effects were estimated by the SCRF PCM method of Tomasi and coworkers (J. Tomasi, M. Persico, Chem. Rev. 94

J. Stare; J. Mavri; G. Ambroži?; D. Hadži

2000-01-01

377

Simple Harmonic Motion in Harmonic Plane Waves.  

ERIC Educational Resources Information Center

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)

Benumof, Reuben

1980-01-01

378

Simple Harmonic Motion in Harmonic Plane Waves.  

ERIC Educational Resources Information Center

|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)|

Benumof, Reuben

1980-01-01

379

Comparison of Three Controllers Applied to Helicopter Vibration.  

National Technical Information Service (NTIS)

A comparison was made of the applicability and suitability of the deterministic controller, the cautious controller, and the dual controller for the reduction of helicopter vibration by using higher harmonic blade pitch control. A randomly generated linea...

J. A. Leyland

1992-01-01

380

Electronic damping of anharmonic adsorbate vibrations at metallic surfaces  

NASA Astrophysics Data System (ADS)

The nonadiabatic coupling of an adsorbate close to a metallic surface leads to electronic damping of adsorbate vibrations and line broadening in vibrational spectroscopy. Here, a perturbative treatment of the electronic contribution to the lifetime broadening serves as a building block for a new approach, in which anharmonic vibrational transition rates are calculated from a position-dependent coupling function. Different models for the coupling function will be tested, all related to embedding theory. The first two are models based on a scattering approach with (i) a jellium-type and (ii) a density functional theory based embedding density, respectively. In a third variant a further refined model is used for the embedding density, and a semiempirical approach is taken in which a scaling factor is chosen to match harmonic, single-site, first-principles transition rates, obtained from periodic density functional theory. For the example of hydrogen atoms on (adsorption) and below (subsurface absorption) a Pd(111) surface, lifetimes of and transition rates between vibrational levels are computed. The transition rates emerging from different models serve as input for the selective subsurface adsorption of hydrogen in palladium starting from an adsorption site, by using sequences of infrared laser pulses in a laser distillation scheme.

Tremblay, Jean Christophe; Monturet, Serge; Saalfrank, Peter

2010-03-01

381

Multiple harmonic plasma emission  

SciTech Connect

A generalized weak turbulence theory for electromagnetic emission at multiple harmonics of the plasma frequency is developed. In the literature, the electromagnetic emission at the plasma frequency and/or its second harmonic has been intensively studied. However, the emission at harmonics higher than the second harmonic is scarcely discussed. In the present paper, the higher harmonic plasma emission is explained by taking the interactions between the transverse mode and electrostatic nonlinear eigenmodes into consideration. The present analysis incorporates electrostatic nonlinear harmonic Langmuir waves into the fully electromagnetic weak turbulence formalism recently reformulated on the basis of the statistical mechanical Klimontovich approach. The wave kinetic equations for the transverse electromagnetic and Langmuir waves interacting with the harmonic Langmuir waves are derived, on the basis of which the emission of electromagnetic waves near multiple harmonics of the plasma frequency is qualitatively discussed.

Yi, Sumin; Yoon, Peter H.; Ryu, Chang-Mo [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of)

2007-01-15

382

Vibrational cooling, heating, and instability in molecular conducting junctions: full counting statistics analysis.  

PubMed

We study current-induced vibrational cooling, heating, and instability in a donor-acceptor rectifying molecular junction using a full counting statistics approach. In our model, electron-hole pair excitations are coupled to a given molecular vibrational mode which is either harmonic or highly anharmonic. This mode may be further coupled to a dissipative thermal environment. Adopting a master equation approach, we confirm the charge and heat exchange fluctuation theorem in the steady-state limit, for both harmonic and anharmonic models. Using simple analytical expressions, we calculate the charge current and several measures for the mode effective temperature. At low bias, we observe the effect of bias-induced cooling of the vibrational mode. At higher bias, the mode effective temperature is higher than the environmental temperature, yet the junction is stable. Beyond that, once the vibrational mode (bias-induced) excitation rate overcomes its relaxation rate, instability occurs. We identify regimes of instability as a function of voltage bias and coupling to an additional phononic thermal bath. Interestingly, we observe a reentrant behavior where an unstable junction can properly behave at a high enough bias. The mechanism for this behavior is discussed. PMID:22824917

Simine, Lena; Segal, Dvira

2012-07-24

383

Harmonization of Biodiesel Specifications  

SciTech Connect

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.

Alleman, T. L.

2008-02-01

384

High-harmonic spectroscopy of molecular isomers  

NASA Astrophysics Data System (ADS)

We demonstrate that high-order-harmonic generation (HHG) spectroscopy can be used to probe stereoisomers of randomly oriented 1,2-dichloroethylene (C2H2Cl2) and 2-butene (C4H8). The high-harmonic spectra of these isomers are distinguishable over a range of laser intensities and wavelengths. Time-dependent numerical calculations of angle-dependent ionization yields for 1,2-dichloroethylene suggest that the harmonic spectra of molecular isomers reflect differences in their strong-field ionization. The subcycle ionization yields for the cis isomer are an order of magnitude higher than those for the trans isomer. The sensitivity in discrimination of the harmonic spectra of cis- and trans- isomers is greater than 8 and 5 for 1,2-dichloroethylene and 2-butene, respectively. We show that HHG spectroscopy cannot differentiate the harmonic spectra of the two enantiomers of the chiral molecule propylene oxide (C3H6O).

Wong, M. C. H.; Brichta, J.-P.; Spanner, M.; Patchkovskii, S.; Bhardwaj, V. R.

2011-11-01

385

Structural and Machinery Vibrations of Hydrofoil Ships.  

National Technical Information Service (NTIS)

A study was made of the structural and machinery characteristics of several hydrofoil ships in order to determine parameters which are of main importance for vibration analyses. A preliminary hull vibration calculation of a hydrofoil ship was performed. I...

D. C. Robinson

1964-01-01

386

String Vibrations  

NSDL National Science Digital Library

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.

2006-12-29

387

Conformational and vibrational studies of isomeric hydrogen cyanide tetramers by quantum chemical methods  

NASA Astrophysics Data System (ADS)

The results of structural studies and detailed harmonic and anharmonic vibrational analysis on two hydrogen cyanide (HCN) tetramers diaminomaleonitrile (DAMN) and diaminofumaronitrile (DAFN), which are important molecules for understanding the chemistry of interstellar space and nitrile rich environments, are being reported on the basis of density functional theory using second-order perturbation theory. Both the molecules are found to have C1 symmetry. While all the heavy atoms of DAMN lie in the same plane (maximum deviation 6°), the two nitrogen atoms in DAFN are out of plane by about 15°. The two amino groups are tetrahedral and do not have significant bond angle anisotropy. Detailed conformational studies are reported on the two molecules and their possible rotational isomers are identified. Complete vibrational analysis based on harmonic and anharmonic frequencies, intensity of infrared and activity of Raman bands and potential energy distribution over the internal coordinates has been provided for the two molecules. Affect of hydrogen bonding on molecular geometry and frequencies of the Nsbnd H stretch modes has been studied by calculations on the dimers of the two molecules. A close agreement has been observed between the experimental and calculated frequencies. Vibrational-rotational constants such as rotational constants in the ground vibrational state (A0, B0, C0) and the effective rotational constants (Ae, Be and Ce), including terms due to quartic centrifugal distortion constants, rotation-vibration coupling constants, Wilson and Nielsen's centrifugal distortion constants have been calculated using B3LYP and B97-1 functionals and 6-31G**, 6-311+G** and TZVP basis sets.

Gupta, V. P.; Tandon, Poonam

2012-04-01

388

High-order harmonic generation from atoms and ions in the high intensity regime  

Microsoft Academic Search

We present calculated optical harmonic spectra for atoms and ions in the high intensity regime to current short-pulse experiments. We find that ions can produce harmonics comparable in strength to those obtained from neutrals, and that the emission extends to much higher order. Simple scaling laws for the strength of the harmonic emission and the maximum observable harmonic are suggested.

Jeffrey Krause; Kenneth Schafer; Kenneth Kulander

1992-01-01

389

Influence of temperature on wideband water spectra: Semi-phenomenological calculation  

NASA Astrophysics Data System (ADS)

The results of analytical calculation of the complex permittivity ? and of the absorption coefficient ? are presented for the temperature range extending from -5.6 °C for supercooled water to 81.4 °C. Dielectric response is modeled by two water fractions with lifetimes from 0.1 to 0.25 ps. One fraction comprises rigid permanent dipoles librating rather freely in a narrow and deep hat-like potential well and the other fraction comprises H-bonded charged molecules performing: (a) fast elastic vibrations along the hydrogen bond; (b) elastic reorientations around this bond; and (c) non-harmonic bending vibration perpendicular to the H-bond. At low temperature the latter vibration is characterized by a noticeable association of water molecules. The calculation reveals the break in continuity of some fitted model parameters occurring in water at the temperature ?300 K.

Gaiduk, Vladimir I.; Crothers, Derrick S. F.

2006-10-01

390

Size-extensive vibrational self-consistent field method.  

PubMed

The vibrational self-consistent field (VSCF) method is a mean-field approach to solve the vibrational Schro?dinger equation and serves as a basis of vibrational perturbation and coupled-cluster methods. Together they account for anharmonic effects on vibrational transition frequencies and vibrationally averaged properties. This article reports the definition, programmable equations, and corresponding initial implementation of a diagrammatically size-extensive modification of VSCF, from which numerous terms with nonphysical size dependence in the original VSCF equations have been eliminated. When combined with a quartic force field (QFF), this compact and strictly size-extensive VSCF (XVSCF) method requires only quartic force constants of the ?(4)V/?Q(i)(2)?Q(j)(2) type, where V is the electronic energy and Q(i) is the ith normal coordinate. Consequently, the cost of a XVSCF calculation with a QFF increases only quadratically with the number of modes, while that of a VSCF calculation grows quartically. The effective (mean-field) potential of XVSCF felt by each mode is shown to be harmonic, making the XVSCF equations subject to a self-consistent analytical solution without matrix diagonalization or a basis-set expansion, which are necessary in VSCF. Even when the same set of force constants is used, XVSCF is nearly three orders of magnitude faster than VSCF implemented similarly. Yet, the results of XVSCF and VSCF are shown to approach each other as the molecular size is increased, implicating the inclusion of unnecessary, nonphysical terms in VSCF. The diagrams of the XVSCF energy expression and their evaluation rules are also proposed, underscoring their connected structures. PMID:21992283

Keçeli, Murat; Hirata, So

2011-10-01

391

Interpreting nonlinear vibrational spectroscopy with the classical mechanical analogs of double-sided Feynman diagrams.  

PubMed

Observables in coherent, multiple-pulse infrared spectroscopy may be computed from a vibrational nonlinear response function. This response function is conventionally calculated quantum-mechanically, but the challenges in applying quantum mechanics to large, anharmonic systems motivate the examination of classical mechanical vibrational nonlinear response functions. We present an approximate formulation of the classical mechanical third-order vibrational response function for an anharmonic solute oscillator interacting with a harmonic solvent, which establishes a clear connection between classical and quantum mechanical treatments. This formalism permits the identification of the classical mechanical analog of the pure dephasing of a quantum mechanical degree of freedom, and suggests the construction of classical mechanical analogs of the double-sided Feynman diagrams of quantum mechanics, which are widely applied to nonlinear spectroscopy. Application of a rotating wave approximation permits the analytic extraction of signals obeying particular spatial phase matching conditions from a classical-mechanical response function. Calculations of the third-order response function for an anharmonic oscillator coupled to a harmonic solvent are compared to numerically correct classical mechanical results. PMID:15473771

Noid, W G; Loring, Roger F

2004-10-15

392

Harmonics generated from a DC biased transformer  

SciTech Connect

The paper presents harmonic characteristics of transformer excitation currents under DC bias caused by geomagnetically induced currents (GIC). A newly developed saturation model of a single phase shell form transformer based on 3D finite element analysis is used to calculate the excitation currents. As a consequence, the complete variations of excitation current harmonics with respect to an extended range of GIC bias are revealed. The results of this study are useful in understanding transformers as harmonic sources and the impact on power systems during a solar magnetic disturbance.

Shu Lu; Yilu Liu; Ree, J. De La (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). The Bradley Dept. of Electrical Engineering)

1993-04-01

393

VIBRATIONALLY EXCITED C{sub 6}H  

SciTech Connect

Rotational spectra of the linear carbon chain radical C{sub 6}H in two low-lying excited vibrational states were observed both at millimeter wavelengths in a low-pressure glow discharge and at centimeter wavelengths in a supersonic molecular beam. Two series of harmonically related lines with rotational constants within 0.3% of the {sup 2{Pi}} ground state were assigned to the {sup 2{Sigma}} and {sup 2{Delta}} vibronic components of an excited bending vibrational level. Measurements of the intensities of the lines in the glow discharge indicate that the {sup 2{Sigma}} component lies very close to ground, but the {sup 2{Delta}} component is much higher in energy. The standard Hamiltonian for an isolated {sup 2{Delta}} state with five spectroscopic constants reproduces the observed rotational spectrum, but several high-order distortion terms in the spin-rotation interaction are needed to reproduce the spectrum of the {sup 2{Sigma}} component in C{sub 6}H and C{sub 6}D. The derived spectroscopic constants allow astronomers to calculate the rotational spectra of the {sup 2{Sigma}} and {sup 2{Delta}} states up to 260 GHz to within 0.1 km s{sup -1} or better in equivalent radial velocity.

Gottlieb, C. A.; McCarthy, M. C.; Thaddeus, P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2010-08-15

394

Saturated and subcooled hydrothermal boiling in groundwater flow channels as a source of harmonic tremor  

Microsoft Academic Search

The potential of hydrothermal boiling in groundwater flow channels for generating harmonic tremor (a relatively monochromatic ground vibration associated with volcanic activity) is examined. We use simple ``organ pipe'' theory of normal-mode fluid vibration and fundamental energy considerations to develop a first-order analytical model of a hydrothermal-boiling souce of harmonic tremor. We use this model to estimate order-of-magnitude groundwater flow

Robert C. Leet

1988-01-01

395

Tautomeric purine forms of 2-amino-6-chloropurine (N9H10 and N7H10): structures, vibrational assignments, NBO analysis, hyperpolarizability, HOMO-LUMO study using B3 based density functional calculations.  

PubMed

Two purine tautomers of 2-amino-6-chloropurine (ACP), in labeled as N(9)H(10) and N(7)H(10), were investigated by vibrational spectroscopy and quantum chemical method. The FT-IR and FT-Raman spectra of ACP have been recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The measured spectra were interpreted by aid of a normal coordinate analysis following DFT full geometry optimization and vibrational frequency calculations at B3LYP/6-311++G(d,p) level. First-order hyperpolarizability, HOMO and LUMO energies were calculated at same level of theory. The calculated molecular geometry has been compared with the X-ray data. The observed and calculated frequencies were found in good agreement. The obtained NBO data and second-order perturbation energy values to elucidate the Lewis and non-Lewis types of bonding structures in the purine tautomer N(9)H(10), have indicated the presence of an intramolecular hyperconjucative interaction between lone pair N and N-C bond orbital. PMID:22706099

Balachandran, V; Parimala, K

2012-05-26

396

Vibrational overtone stretching transitions in trimethyl phosophate and triethyl phosophate  

NASA Astrophysics Data System (ADS)

The CH stretching overtone transitions of chemical warfare agents are of interest in the area of threat detection, including standoff threat detection, as many of these transitions occur near regions where small, efficient diode lasers operate. Further, detectors which operate in the regions where CH overtone transitions occur (i.e., in the near infrared and visible regions) are usually much more sensitive than detectors which operate in the region where fundamental CH vibrational transitions occur (i.e., in the mid infrared). However, the interpretation of experimental overtone spectra is complex, and the computational simulation of overtone spectra is challenging. Presented herein are the simulated vapour phase CH overtone stretching transitions in the nerve agent simulants trimethyl phosophate and triethyl phosophate. Spectral regions are simulated using the harmonically coupled anharmonic oscillator (HCAO) model. Data for HCAO calculations are obtained from ab initio calculations, without recourse to experimental data.

Petryk, Michael W. P.

2007-05-01

397

Vibrations of weakly coupled nanoparticles  

Microsoft Academic Search

The vibrations of a coupled pair of isotropic silver spheres are investigated and compared with the vibrations of the single isolated spheres. Situations of both strong coupling and also weak coupling are investigated using continuum elasticity and perturbation theory. The numerical calculation of the eigenmodes of such dimers is augmented with a symmetry analysis. This checks the convergence and applicability

Lucien Saviot; Daniel B. Murray

2010-01-01

398

Vibrational spectral investigation and Natural Bond Orbital analysis of anti-rheumatoid drug Ethyl 4-nitrophenylacetate - DFT approach  

NASA Astrophysics Data System (ADS)

Vibrational analysis of ethyl 4-nitrophenylacetate (ENPA) molecule was carried out using FT-IR and FT-Raman spectroscopic techniques. The equilibrium geometry, harmonic vibrational wave numbers, various bonding features have been computed using density functional theory. The calculated molecular geometry parameters have been compared with XRD data. The detailed interpretation of the vibrational spectra has been carried out by computing Potential Energy Distribution (PED). Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using Natural Bond Orbital (NBO) analysis. The results show that the charge in the electron density (ED) in the ?? and ?? antibonding orbitals and second order delocalization energies (E2) confirm the occurrence of ICT (intramolecular charge transfer) within the molecule. The simulated spectra satisfactorily coincide with the experimental spectra.

Suresh, D. M.; Amalanathan, M.; Sebastian, S.; Sajan, D.; Hubert Joe, I.; Bena Jothy, V.

2012-12-01

399

Intermolecular charge transfer and vibrational analysis of hydrogen bonding in acetazolamide.  

PubMed

In the present work the structural and spectral characteristics of acetazolamide have been studied by methods of infrared, Raman spectroscopy and quantum chemistry. Electrostatic potential surface, optimized geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by density functional theory (DFT) employing B3LYP with complete relaxation in the potential energy surface using 6-311++G(d,p) basis set. Based on these results, we have discussed the correlation between the vibrational modes and the structure of the dimers of acetazolamide. The calculated vibrational spectra of three dimers of acetazolamide have been compared with observed spectra, and the assignment of observed bands was carried out using potential energy distribution. The observed spectra agree well with the values computed from the DFT. A comparison of observed and calculated vibrational spectra clearly shows the effect of hydrogen bonding. The frequency shifts observed for the different dimers are in accord with the hydrogen bonding in acetazolamide. Natural bond orbital (NBO) analyses reflect the charge transfer interaction in the individual hydrogen bond units and the stability of different dimers of acetazolamide. PMID:23063858

Chaturvedi, Deepika; Gupta, Vineet; Tandon, Poonam; Sharma, Anamika; Baraldi, C; Gamberini, M C

2012-09-12

400

Vibrational spectroscopic investigations and computational study of 5-tert-Butyl-N-(4-trifluoromethylphenyl)pyrazine-2-carboxamide  

NASA Astrophysics Data System (ADS)

Pyrazine and its derivatives form an important class of compounds present in several natural flavors and complex organic molecules. Quantum chemical calculations of the equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman activities of 5-tert-Butyl-N-(4-trifluoromethylphenyl)pyrazine-2-carboxamide in the ground state were carried out by using density functional methods. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. Nonlinear optical behavior of the examined molecule was investigated by the determination of first hyperpolarizability. The calculated HOMO and LUMO energies show the chemical activity of 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 that of similar derivatives. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis.

Joseph, Tomy; Varghese, Hema Tresa; Yohannan Panicker, C.; Viswanathan, K.; Dolezal, Martin; Manojkumar, T. K.; Alsenoy, Christian Van

2013-09-01

401

Calculation of the adjoint masses for an annular blade assembly  

SciTech Connect

It is necessary to know the adjoint-mass coefficients in order to solve various problems in turbine aeroelasticity such as the calculation of the natural frequencies and forms of blade vibrations. These coefficients are known only for the planar set of plates, so interest attaches to estimating the effects of the three-dimensional flow on their magnitudes. Here the authors consider the adjoint masses for a three-dimensional ring set of thin blades performing small harmonic oscillations with a constant phase shift in an incompressible fluid.

Tkacheva, L.A.

1984-03-01

402

Extracting vibrational information from rotational spectra-A microwave investigation on excited vibrational states of SF4  

NASA Astrophysics Data System (ADS)

A method of extracting harmonic information from the inertial defects of non-totally symmetric vibrational states of orthorhombic molecules has been developed. As a result it has been possible to exploit additional information for a normal coordinate analysis. This information has been obtained from microwave-microwave double resonance experiments on SF4 in excited vibrational states.

Christen, Dines

1992-01-01

403

Mathematical model of low-frequency electromagnetic horizontal vibration platform  

NASA Astrophysics Data System (ADS)

In this paper, the mathematical model of low frequency electromagnetic vibration platform is established on the basis of its mechanical structure and electrical structure. Its frequency response characteristics are also analyzed in detail. The correctness of the mathematical model is verified by a lot of testing data. Subsequently, nonlinear factors of the vibration platform are discussed, including magnetic field's nonlinear, moving-coil response and nonlinear output of power amplifiers, and so on. These factors lead to a lot of harmonic vibration and severe vibration waveform distortion. Some measures to decrease the magnetic field's nonlinear and the effect of moving-coil response are proposed for the low frequency electromagnetic vibration platform.

Li, Xiaolei; Fan, Shangchun

2003-09-01

404

Vibrational dynamics of tricyanomethanide  

NASA Astrophysics Data System (ADS)

Steady-state and time resolved IR spectroscopy have been used to characterize vibrational spectra and relaxation dynamics of the antisymmetric CN stretching band of tricyanomethanide (TCM) in solutions of water, heavy water, methanol, dimethyl sulfoxide, formamide, and the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]. The vibrational energy relaxation times for tricyanomethanide in these solvents are longer than those previously reported for dicyanamide, another CN containing anion, in the same solvents. Results of ab initio calculations of the vibrational frequencies for tricyanomethanide depend on the method used and compare favorably with experimentally measured values for IR-active and Raman-active bands. Proton and electron affinities were also calculated.

Weidinger, Daniel; Houchins, Cassidy; Owrutsky, Jeffrey C.

2012-02-01

405

Active Harmonic Filters  

Microsoft Academic Search

Unlike traditional passive harmonic filters, modern active harmonic filters have the following multiple functions: harmonic filtering, damping,isolation and termination, reactive-power control for power factor correction and voltage regulation, load balancing, voltage-flicker reduction, and\\/or their combinations. Significant cost reductions in both power semiconductor devices and signal processing devices have inspired manufactures to put active filters on the market. This paper deals

HIROFUMI AKAGI

2005-01-01

406

Franck-Condon factors based on anharmonic vibrational wave functions of polyatomic molecules.  

PubMed

Franck-Condon (FC) integrals of polyatomic molecules are computed on the basis of vibrational self-consistent-field (VSCF) or configuration-interaction (VCI) calculations capable of including vibrational anharmonicity to any desired extent (within certain molecular size limits). The anharmonic vibrational wave functions of the initial and final states are expanded unambiguously by harmonic oscillator basis functions of normal coordinates of the respective electronic states. The anharmonic FC integrals are then obtained as linear combinations of harmonic counterparts, which can, in turn, be evaluated by established techniques taking account of the Duschinsky rotations, geometry displacements, and frequency changes. Alternatively, anharmonic wave functions of both states are expanded by basis functions of just one electronic state, permitting the FC integral to be evaluated directly by the Gauss-Hermite quadrature used in the VSCF and VCI steps [Bowman et al., Mol. Phys. 104, 33 (2006)]. These methods in conjunction with the VCI and coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] method have predicted the peak positions and intensities of the vibrational manifold in the X 2B1 photoelectron band of H2O with quantitative accuracy. It has revealed that two weakly visible peaks are the result of intensity borrowing from nearby states through anharmonic couplings, an effect explained qualitatively by VSCF and quantitatively by VCI, but not by the harmonic approximation. The X 2B2 photoelectron band of H2CO is less accurately reproduced by this method, likely because of the inability of CCSD(T)/cc-pVTZ to describe the potential energy surface of open-shell H2CO+ with the same high accuracy as in H2O+. PMID:16863289

Rodriguez-Garcia, Valerie; Yagi, Kiyoshi; Hirao, Kimihiko; Iwata, Suehiro; Hirata, So

2006-07-01

407

Matrix-isolation FT-IR study and theoretical calculations of the vibrational, tautomeric and H-bonding properties of hypoxanthine  

Microsoft Academic Search

The neutral compound hypoxanthine is investigated using the technique of matrix-isolation FT-IR spectroscopy combined with density functional theory (DFT) and ab initio methods. Two theoretical methods (RHF and DFT\\/B3-LYP) are compared for vibrational frequency prediction, and four methods (RHF\\/\\/RHF, MP2\\/\\/RHF, DFT\\/\\/DFT and MP2\\/\\/DFT) for prediction of the relative energies of the tautomers and the interaction energies of the complexes. All

R. Ramaekers; G Maes; L Adamowicz; A Dkhissi

2001-01-01

408

Lowest Energy Vibrational Modes of Nine Naphthalene Derivatives; Experiment and Theory  

NASA Astrophysics Data System (ADS)

FIR gas phase absorption spectra of nine naphthalene derivatives (azulene, quinoline, isoquinoline, biphenyl, diphenylmethane, bibenzyl, 2-, 3-, and 4-phenyltoluene) have been recorded at medium resolution (0.5 wn) using a Fourier transform Bruker IFS125 interferometer located on the AILES beamline of SOLEIL synchrotron. Assignments of these weak vibrational bands were performed using density-functional theory calculations carried out at the harmonic and anharmonic levels (B97-1/6-311G(d,p)). Molecular structure dependence of the FIR spectra is discussed based on the comparative study of several selected FIR modes.

Martin-Drumel, M. A.; Pirali, O.; Laquais, Y.; Falvo, C.; Parneix, P.; Brechignac, Ph.

2013-06-01

409

Active vibration control of an oscillating rigid bar using nonlinear output regulation techniques  

Microsoft Academic Search

The work describes the attenuation problem of vibrations affecting a nonlinear oscillatory mechanical system using passive and active vibration control methods based on nonlinear techniques. The mechanical system consists of an oscillating rigid bar coupled to a passive absorber. The undesirable vibration is a harmonic torque, with variable frequency, applied to the bar. The main goal consists of the design

Benjamin Vazquez; Gerardo Silva; Jaime Alvarez

2000-01-01

410

Friction-induced vibration — with and without external disturbance  

Microsoft Academic Search

The dynamics of friction-induced vibration resulting from a velocity-dependent friction characteristic is studied theoretically and experimentally. The frictional system is further studied in the presence of an external dynamic force. The amplitude of quasi-harmonic vibration is shown to increase with sliding velocity until oscillation ceases at some upper velocity boundary depending on the friction characteristic. The vibration, which can exist

P. L. Ko; Marie-Claude Taponat; Rodolphe Pfaifer

2001-01-01

411

Vibration energy harvesting from random force and motion excitations  

Microsoft Academic Search

A vibration energy harvester is typically composed of a spring–mass system with an electromagnetic or piezoelectric transducer connected in parallel with a spring. This configuration has been well studied and optimized for harmonic vibration sources. Recently, a dual-mass harvester, where two masses are connected in series by the energy transducer and a spring, has been proposed. The dual-mass vibration energy

Xiudong Tang; Lei Zuo

2012-01-01

412

The Study of Damped Harmonic Oscillations Using an Electronic Counter  

ERIC Educational Resources Information Center

|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…

Wadhwa, Ajay

2009-01-01

413

PREFACE: Vibrations at surfaces Vibrations at surfaces  

NASA Astrophysics Data System (ADS)

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

Rahman, Talat S.

2011-12-01

414

Analysis of Vibration and Acoustic Noise in Permanent Magnet Motors.  

NASA Astrophysics Data System (ADS)

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.

Hwang, Sangmoon

415

Geometrical Theory of Spherical Harmonics for Geosciences  

NASA Astrophysics Data System (ADS)

Spherical harmonics play a central role in the modelling of spatial and temporal processes in the system Earth. The gravity field of the Earth and its temporal variations, sea surface topography, geomagnetic field, ionosphere etc., are just a few examples where spherical harmonics are used to represent processes in the system Earth. We introduce a novel method for the computation and rotation of spherical harmonics, Legendre polynomials and associated Legendre functions without making use of recursive relations. This novel geometrical approach allows calculation of spherical harmonics without any numerical instability up to an arbitrary degree and order, e.g. up to degree and order 106 and beyond. The algorithm is based on the trigonometric reduction of Legendre polynomials and the geometric rotation in hyperspace. It is shown that Legendre polynomials can be computed using trigonometric series by pre-computing amplitudes and translation terms for all angular arguments. It is shown that they can be treated as vectors in the Hilbert hyperspace leading to unitary hermitian rotation matrices with geometric properties. Thus, rotation of spherical harmonics about e.g. a polar or an equatorial axis can be represented in the similar way. This novel method allows stable calculation of spherical harmonics up to an arbitrary degree and order, i.e. up to degree and order 106 and beyond.

Svehla, Drazen

2010-05-01

416

The Shock and Vibration Bulletin.  

National Technical Information Service (NTIS)

Contents: Analysis of random responses for calculation of fatigue damage; Vibration trends analysis; Radiation resistance of cylindrical shells exhibiting axisymmetric mode shapes; Modal sensitivity study of a conical reentry vehicle to aerodynamically in...

1969-01-01

417

Classical harmonic generation in rare gases  

SciTech Connect

The classical microcanonical ensemble approach to high-harmonic generation (HHG) in rare gases subjected to intense laser fields is studied. We show that the ensemble spectrum is a ''sampled'' version of the single trajectory spectrum. Unlike the radiation of the single ensemble member, the total ensemble radiation possesses all the basic HHG features: odd laser harmonics, plateau, and cutoff. The sampling theorem for uniform grids is used to explain why the ensemble spectrum can be computed accurately with a very small number of ensemble members compared to the Monte Carlo method. Furthermore, The phase space relevant to harmonic generation is found to be significantly smaller than the field free microcanonical ensemble. In addition we demonstrate the seeding effect that was predicted and observed in quantum simulation. For circular polarization, we verify that the harmonic generation is highly suppressed even when the argument of the three-step model does not apply. All the findings are numerically calculated for the xenon atom.

Uzdin, Raam; Moiseyev, Nimrod [Department of Physics, Technion, Israel Institute of Technology (Israel)

2010-06-15

418

Additional calculations of triton moments  

NASA Astrophysics Data System (ADS)

The formalism of hyperspherical harmonics is used to calculate several moments of the triton photoeffect for a Volkov potential with Serber exchange. The accuracy of Clare's calculations of moments ?0 and ?1 is improved by including more terms in the hyperspherical harmonic expansion of the potential and of the ground state wave function. The moment ?2=8.9×104 MeV3 mb is calculated using one term in the hyperspherical harmonic expansions of the potential and wave function. We invert four moments and find reasonable agreement with Gorbunov's measurements of the 3He photoeffect. NUCLEAR REACTIONS Triton photoeffect, hyperspherical harmonics, moments of photoeffect, inversion of moments.

Lally, D. F.; Levinger, J. S.

1982-02-01

419

Ultrasound vibrometry using orthogonal- frequency-based vibration pulses.  

PubMed

New vibration pulses are developed for shear wave generation in a tissue region with preferred spectral distributions for ultrasound vibrometry applications. The primary objective of this work is to increase the frequency range of detectable harmonics of the shear wave. The secondary objective is to reduce the required peak intensity of transmitted pulses that induce the vibrations and shear waves. Unlike the periodic binary vibration pulses, the new vibration pulses have multiple pulses in one fundamental period of the vibration. The pulses are generated from an orthogonal-frequency wave composed of several sinusoidal signals, the amplitudes of which increase with frequency to compensate for higher loss at higher frequency in tissues. The new method has been evaluated by studying the shear wave propagation in in vitro chicken and swine liver. The experimental results show that the new vibration pulses significantly increase tissue vibration with a reduced peak ultrasound intensity, compared with the binary vibration pulses. PMID:24158291

2013-11-01

420

Vibrational relaxation of anharmonic oscillator molecules: Relaxation under isothermal conditions  

Microsoft Academic Search

The problem of the vibrational relaxation of a system of anharmonic oscillator molecules has been analysed numerically. Exchange of vibrational energy between molecules plays an important part in the relaxation mechanism. Calculations have been carried out for nitrogen, using transition probabilities similar to those calculated by Schwartz et al. These calculations show that, during vibrational excitation, the relaxation rate is

K N C Bray

1968-01-01

421

Microwave and vibrational spectra, ab initio calculations, conformational stabilities and assignments of the fundamentals of the C s conformer of n-butylgermane  

Microsoft Academic Search

The FT-microwave spectrum of n-butylgermane, CH3CH2CH2CH2GeH3 has been investigated from 4000 to 18,000MHz and the microwave spectra have been observed for all of the five naturally occurring germanium isotopologues for the anti–anti (aa) conformer. The dipole moment for the 74Ge containing species has been measured, giving a total dipole moment of 0.881 (26)D. In addition, the vibrational spectrum of n-butylgermane

Arthur J. LaPlante; Howard D. Stidham; Sean A. Peebles; Rebecca A. Peebles; Charles J. Wurrey; Gamil A. Guirgis

2011-01-01

422

Structural, vibrational, electronic, NMR, NLO and reactivity analyses of (3Z)-3-(2-oxo-2-phenylethylidene)-1,3-dihydro-2H-indol-2-one (OPEDI) by ab initio HF and DFT calculations.  

PubMed

This study represents the vibrational, electronic, NMR, NLO, reactivity and structural aspects of (3Z)-3-(2-oxo-2-phenylethylidene)-1,3-dihydro-2H-indol-2-one (OPEDI). A detailed interpretation of the FT-IR, FT-Raman, UV and NMR spectra were reported. Theoretical calculations were performed by ab initio HF and density functional theory (DFT)/B3LYP method using 6-311++G(d,p) basis sets. The most preferred Z isomer (cis-configuration) was confirmed through PES scan studies. The vibrational wavenumbers and potential energy distribution (PED) of various normal modes were calculated. The lower frontier orbital energy gap and high dipole moment of OPEDI illustrates the high reactivity. The stability and charge delocalization of the molecule was stud