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1

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

E-print Network

magnetometer Ian J. Daniel and Damian P. Hampshire Department of Physics, Superconductivity Group, University inhomogeneity of the magnet on a vibrating sample magnetometer VSM measure- ment of a superconductor measurements on superconductors using a Vi- brating Sample Magnetometer12 VSM . Harmonic VSM measurements

Hampshire, Damian

2

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

SciTech Connect

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

Miliordos, Evangelos; Xantheas, Sotiris S.

2013-08-15

3

An Application of Error Reduction and Harmonic Inversion schemes to the Semiclassical Calculation of Molecular Vibrational Energy Levels  

NASA Astrophysics Data System (ADS)

A singular value decomposition based harmonic inversion (HI) signal processing scheme is applied to the semiclassical initial value representation (IVR) calculation of molecular vibrational states. Relative to usual IVR procedure of Fourier analysis of a signal made from the Monte Carlo evaluation of the phase space integral in which many trajectories are needed, the new procedure obtains acceptable results with many fewer trajectories. Calculations are carried out for vibrational energy levels of H2O to illustrate the overall procedure. New results are given for the zero point energy (ZPE) of CH5+.

Taylor, Howard S.

2005-03-01

4

Vibrational spectroscopy of (SO42-).(H2O)n clusters, n=1-5: Harmonic and anharmonic calculations and experiment  

Microsoft Academic Search

The vibrational spectroscopy of (SO42-).(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

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

2007-01-01

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

Vibrational spectroscopy of (SO42-).(H2O)n clusters, n=1-5: Harmonic and anharmonic calculations and experiment  

NASA Astrophysics Data System (ADS)

The vibrational spectroscopy of (SO42-)•(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 540-1850cm-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 (SO42-)•(H2O)5: The global minimum of the potential energy corresponds to a Cs 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 ?5.

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

2007-09-01

8

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

9

Application of Higher Harmonic Blade Feathering on the OH-6A Helicopter for Vibration Reduction.  

National Technical Information Service (NTIS)

The design, implementation, and flight test results of higher harmonic blade feathering for vibration reduction on the OH-6A helicopter are described. The higher harmonic control (HHC) system superimposes fourth harmonic inputs upon the stationary swashpl...

F. K. Straub, E. V. Byrns

1986-01-01

10

Harmonic influence lines in structural dynamics calculated by use of Müller-Breslau's theorem  

NASA Astrophysics Data System (ADS)

Müller-Breslau's theorem is formulated and proved for certain linear structures in forced stationary harmonic vibration. The theorem provides the structural analyst with a computationally attractive method for finding, in one and the same calculation, all coefficients (generally complex-valued) describing the influence on a reactive or sectional force in a fixed position by an external harmonic unit load acting in any position. Critical and dimensioning combinations of loads can thereby easily be found. Three numerical examples demonstrate applications to systems that are discrete and continuous, undamped and damped, and finite and infinite. It is shown how a standard computer program for the analysis of beam and frame vibration can be employed to calculate and plot harmonic influence lines by use of the Müller-Breslau technique. Physical experiments based on the same technique are discussed.

Åkesson, B. Å.

1990-10-01

11

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

12

Harmonic Torque Calculation of Induction Motors Using Electromagnetic Field Analysis  

NASA Astrophysics Data System (ADS)

In this paper, we investigate effects of harmonic electromagnetic field to torque characteristics of induction motors from both side of experiment and electromagnetic field analysis. The characteristics of two kinds of the aluminum cage three-phase induction motors are measured and calculated. One is with the closed rotor slots. The other is semi-closed. In the experiment, the negative torque at synchronous speed is measured by driving the induction motor by the synchronous permanent magnet motor. The total torque at load condition is also measured by the torque detector. In the analysis, the harmonic magnetic fields, the harmonic losses and the harmonic torques at each time and space harmonic order are calculated using the nonlinear time-stepping finite element method to clarify the mechanism of the harmonic torque generation. The measured and the calculated results agree well. It is clarified that the negative torque caused by the slot harmonics at the rated load condition is not negligible and that the negative torque is mainly generated by the harmonic core losses.

Yamazaki, Katsumi; Haruishi, Yoshihisa; Ara, Takahiro

13

Ab initio calculation of harmonic force fields and vibrational spectra for the arsine oxides and sulfides R sub 3 AsY (R = H, F; Y = O, S) and related compounds  

SciTech Connect

Ab initio self-consistent-field calculations using effective core potentials and polarized double-zeta basis sets are reported for the arsenic compounds H{sub 3}As, H{sub 3}AsO, H{sub 3}AsS, F{sub 3}As, F{sub 3}AsO, F{sub 3}AsS, cis- and trans-H{sub 2}AsOH, and HAsO. The calculated geometries, rotational constants, vibrational frequencies, Coriolis coupling constants, centrifugal distortion constants, infrared band intensities, and force fields are compared with the available experimental data. Good agreement is found in the case of the known molecules, especially H{sub 3}As and F{sub 3}As, so that the predictions for the unknown molecules are expected to be realistic. The theoretical results confirm a recent spectroscopic identification of H{sub 3}AsO, H{sub 2}AsOH, and HAsO and suggest reassignment of several observed frequencies.

Schneider, W.; Thiel, W. (Bergische Universitaet-Gesamthochschule, Wuppertal (West Germany)); Komornicki, A. (Polyatomics Research Institute, Mountain View, CA (USA))

1990-04-05

14

Harmonic Torque Calculation of Induction Motors Using Electromagnetic Field Analysis  

Microsoft Academic Search

In this paper, we investigate effects of harmonic electromagnetic field to torque characteristics of induction motors from both side of experiment and electromagnetic field analysis. The characteristics of two kinds of the aluminum cage three-phase induction motors are measured and calculated. One is with the closed rotor slots. The other is semi-closed. In the experiment, the negative torque at synchronous

Katsumi Yamazaki; Yoshihisa Haruishi; Takahiro Ara

2004-01-01

15

Multi-channel Electronic and Vibrational Dynamics in Polyatomic High-order Harmonic Generation  

E-print Network

High-order harmonic generation in polyatomic molecules generally involves multiple channels, each associated with a different orbital. Their unambiguous assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach, using unaligned SF$_6$ molecules as an example, where we combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Channel-resolved above-threshold ionization measurements reveal that strong-field ionization opens four channels. Two of them, identified by monitoring the ellipticity dependence of the high-harmonic emission, are found to dominate the harmonic signal. A switch from the HOMO-3 to the HOMO-1 channel at 26 eV is confirmed by a phase jump in the harmonic emission, and by the differing dynamical responses to molecular vibrations. This study demonstrates a modus operandi for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected.

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

2014-01-01

16

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

17

Accurate calculation of high harmonics generated by relativistic Thomson scattering  

NASA Astrophysics Data System (ADS)

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 solution of this problem. Taking into account the Liènard-Wiechert equations, we obtain a periodic scattered electromagnetic field. Without loss of generality, the solution is strongly simplified by observing that the electromagnetic field is always normal to the direction electron-detector. The Fourier series expansion of this field leads to accurate expressions of the high harmonics generated by the Thomson scattering. Our calculations lead to a discrete HHG spectrum, whose shape and angular distribution are in agreement with the experimental data from the literature. Since no approximations were made, our approach is also valid in the ultrarelativistic regime, corresponding to intensities higher than 1023 W cm-2, where it predicts a strong increase of the HHG intensities and of the order of harmonics. In this domain, the nonlinear Thomson scattering could be an efficient source of hard x-rays.

Popa, Alexandru

2008-01-01

18

Efficient calculation of anharmonic vibrational spectra of large molecules with localized modes.  

PubMed

The analysis and interpretation of the vibrational spectra of complex (bio)molecular systems, such as polypeptides and proteins, requires support from quantum-chemical calculations. Such calculations are currently restricted to the harmonic approximation. Here, we show how one of the main bottlenecks in such calculations, the evaluation of the potential energy surface, can be overcome by using localized modes instead of the commonly employed normal modes. We apply such local vibrational self-consistent field (L-VSCF) and vibrational configuration interaction (L-VCI) calculations to a cyclic water tetramer and a helical hexa-alanine peptide. The results show that the use of localized modes is equivalent to the commonly used normal modes, but offers several advantages. First, a faster convergence with respect to the excitation level is observed in L-VCI calculations. Second, the localized modes provide a reduced representation of the couplings between modes that show a regular coupling pattern. This can be used to disregard a significant number of small two-mode potentials a priori. Several such reduced coupling approximations are explored, and we show that the number of single-point calculations required to evaluate the potential energy surface can be significantly reduced without introducing noticeable errors in the resulting vibrational spectra. PMID:25080397

Panek, Pawe? T; Jacob, Christoph R

2014-10-20

19

Nonlinear vibrations of thin arbitrarily laminated composite plates subjected to harmonic excitations using DKT elements  

NASA Technical Reports Server (NTRS)

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.

Chiang, C. K.; Xue, David Y.; Mei, Chuh

1993-01-01

20

Calculation of unsteady linearized Euler flows in cascades using harmonically deforming grids  

NASA Technical Reports Server (NTRS)

A method for calculating unsteady, inviscid, compressible flows in cascades is presented. Using the linearized Euler technique, the flow is decomposed into a steady or mean flow plus a harmonically varying small disturbance flow. The equations that describe the small disturbance flow are linear variable coefficient equations, and are solved using a pseudo-time time marching Lax-Wendroff technique. Unlike previous linearized methods, however, the solution is computed on a harmonically deforming computational grid that conforms to the motion of the vibrating airfoils. The mean flow and perturbation flow solutions are defined in the deforming coordinate system rather than in a coordinate system fixed in space. Hence, no extrapolation terms are required to implement the upwash boundary conditions at the airfoil surfaces, significantly improving the accuracy of the method. For transonic flow calculations, unsteady shock motions are modelled using shock capturing. The unsteady loads due to the shock motion are then seen as pressure impulses. Representative computational results are presented for transonic channel flows and subsonic and transonic cascade flows.

Hall, Kenneth C.; Clark, William S.

1991-01-01

21

Multi-harmonic measurements and numerical simulations of nonlinear vibrations of a beam with non-ideal boundary  

E-print Network

Multi-harmonic measurements and numerical simulations of nonlinear vibrations of a beam with non This study presents a direct comparison of measured and predicted nonlinear vibrations of a clamped with measurements is performed in the vicinity of the primary resonance. First of all, a nonlinear analytical model

Boyer, Edmond

22

Calculation of vibrational zero-point energy  

Microsoft Academic Search

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

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

2001-01-01

23

Phase transition and thermodynamic properties of ThO2: Quasi-harmonic approximation calculations and anharmonic effects  

NASA Astrophysics Data System (ADS)

The thermodynamic properties and the phase transition of ThO2 from the cubic structure to the orthorhombic structure are investigated using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon calculations. The anharmonic contribution to quasi-harmonic free energy is accounted for by using an effective method (2010 Phys. Rev. B 81 172301). The results reveal that at ambient temperature, the phase transition from the cubic phase to the orthorhombic phase occurs at 26.45 GPa, which is consistent with the experimental and theoretical data. With increasing temperature, the transition pressure decreases almost linearly. By comparing the experimental results with the calculation results, it is shown that the thermodynamic properties of ThO2 at high temperature improve substantially after including the anharmonic correction to quasi-harmonic free energy.

Li, Qiang; Yang, Jun-Sheng; Huang, Duo-Hui; Cao, Qi-Long; Wang, Fan-Hou

2014-01-01

24

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

NASA Astrophysics Data System (ADS)

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

Barton, Dennis; König, Carolin; Neugebauer, Johannes

2014-10-01

25

Magnetostrictive vibrations model of a three-phase transformer core and the contribution of the fifth harmonic in the grid voltage  

NASA Astrophysics Data System (ADS)

The effect of the fifth harmonic in the grid voltage (with fundamental frequency of 50 Hz) on the vibrations of a three-phase transformer core is computed, since such harmonic has the largest contribution in the European grid voltage. The computational method is a two-dimensional (2D) finite element technique. The modal vibrations under various magnetisations (viz with different fifth harmonic components) are compared with those obtained under a purely sinusoidal magnetisation and showed that the variations for the 100 Hz harmonic of the vibrations are small. However, the 200 Hz harmonic showed a significant increase when a fifth harmonic was present on the applied voltage. In fact, the presence of a fundamental component with 50 Hz frequency and a fifth harmonic on the magnetisation signal generates a 200 Hz harmonic on the magnetostriction strains (and the magnetic forces), and thus this harmonic increases significantly.

Gorji Ghalamestani, Setareh; Vandevelde, Lieven; Dirckx, Joris J. J.; Melkebeek, Jan A. A.

2014-05-01

26

REGULAR PAPER Vibrational mode frequency calculations of chlorophyll-d  

E-print Network

REGULAR PAPER Vibrational mode frequency calculations of chlorophyll-d for assessing (P740+ -P740 that utilizes chlorophyll-d for light induced photochemistry. In photosystem I particles from Acary- ochloris marina, the primary electron donor is called P740, and it is thought that P740 consist of two chlorophyll

Hastings, Gary

27

Multi-harmonic measurements and numerical simulations of nonlinear vibrations of a beam with non-ideal boundary conditions  

NASA Astrophysics Data System (ADS)

This study presents a direct comparison of measured and predicted nonlinear vibrations of a clamped-clamped steel beam with non-ideal boundary conditions. A multi-harmonic comparison of simulations with measurements is performed in the vicinity of the primary resonance. First of all, a nonlinear analytical model of the beam is developed taking into account non-ideal boundary conditions. Three simulation methods are implemented to investigate the nonlinear behavior of the clamped-clamped beam. The method of multiple scales is used to compute an analytical expression of the frequency response which enables an easy updating of the model. Then, two numerical methods, the Harmonic Balance Method and a time-integration method with shooting algorithm, are employed and compared one with each other. The Harmonic Balance Method enables to simulate the vibrational stationary response of a nonlinear system projected on several harmonics. This study then proposes a method to compare numerical simulations with measurements of all these harmonics. A signal analysis tool is developed to extract the system harmonics' frequency responses from the temporal signal of a swept sine experiment. An evolutionary updating algorithm (Covariance Matrix Adaptation Evolution Strategy), coupled with highly selective filters is used to identify both fundamental frequency and harmonic amplitudes in the temporal signal, at every moment. This tool enables to extract the harmonic amplitudes of the output signal as well as the input signal. The input of the Harmonic Balance Method can then be either an ideal mono-harmonic signal or a multi-harmonic experimental signal. Finally, the present work focuses on the comparison of experimental and simulated results. From experimental output harmonics and numerical simulations, it is shown that it is possible to distinguish the nonlinearities of the clamped-clamped beam and the effect of the non-ideal input signal.

Claeys, M.; Sinou, J.-J.; Lambelin, J.-P.; Alcoverro, B.

2014-12-01

28

Calculation of natural and forced vibrations of a piping system. Part 2. Dynamic stiffness of a pipe bend  

Microsoft Academic Search

The notion of the dynamic flexibility factor of a pipe bend to be used in problems on the calculation of harmonic vibrations\\u000a of pipelines is formulated. Based on the Vlasov semi-momentless theory, simplifying hypotheses are introduced that make it\\u000a possible to reduce the problem statement to the solution of the quartic differential equation. Using the results of the dynamic\\u000a analysis

I. V. Orynyak; S. A. Radchenko; A. S. Batura

2007-01-01

29

Intermolecular vibrations of different isotopologs of the water dimer: Experiments and density functional theory calculations  

NASA Astrophysics Data System (ADS)

Far infrared spectra of seven different isotopologs of the water dimer have been measured in neon matrices at 2.8 K. The experiments are interpreted with the aid of density functional theory calculations, in particular the calculated harmonic isotopic shifts were utilized. All six intermolecular vibrational modes of the water dimer and the fully deuterated water dimer are assigned based the isotopic shifts induced. 31 of a total of 42 intermolecular fundamental modes of the seven different H, D, and 18O containing water dimers have been experimentally observed and assigned accordingly. The overall agreement between the calculations and the experiments of all isotopologs results in a complete and consistent description of these modes.

Ceponkus, J.; Uvdal, P.; Nelander, B.

2008-11-01

30

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

31

Molecular structure and vibrational spectra of ibuprofen using density function theory calculations  

NASA Astrophysics Data System (ADS)

The molecular geometry and the theoretical harmonic frequencies and infrared intensities of ibuprofen were calculated for all the molecules using five different density functional methods (mPW1PW91, B3PW91, B3LYP, HCTH and LSDA) with five basic sets, including 6-311G, 6-311++G, 6-311+G (d, p), 6-311++G (d, p) and 6-311++G (2d, 2p). The purpose of this research was to compare the performance of different DFT methods at different basis sets in predicting geometry and vibration spectrum of ibuprofen. The optimized geometric band lengths and bond angles obtained by using mPW1PW91 at 6-311++G (d, p) and 6-311++G (2d, 2p) basic sets show the best agreement with the experimental data. Comparison of the observed fundamental vibrational frequencies of ibuprofen with calculated results indicates that the B3PW91/6-311++G (2d, 2p) level is superior to all the remaining levels for predicting all the vibration spectra on average for ibuprofen.

Liu, Lekun; Gao, Hongwei

2012-04-01

32

A novel fuzzy number based method to model aggregate loads for harmonic load-flow calculation  

Microsoft Academic Search

Harmonic distortion is a growing problem in power systems due to the increasing use of power electronic devices and loads. A possibilistic methodology for harmonic load-flow calculations based on fuzzy numbers has recently been proposed by the authors as an alternative to probabilistic approaches for modeling uncertainties in linear and nonlinear loads. This paper presents a methodology to aggregate uncertainly

A. A. Romero; H. C. Zini; G. Ratta; R. Dib

2008-01-01

33

Molecular structure and vibrational spectroscopic investigation of melamine using DFT theory calculations.  

PubMed

The FT-Raman and FT-IR spectra for melamine have been recorded in the region 4000-100cm(-1) and 4000-400cm(-1), respectively compared with the harmonic vibrational frequencies calculated using density functional theory method (B3LYP) by employing 6-31G(d,p) and 6-311++G(d,p) basis set with appropriate scaling factors. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values. The experimental geometrical parameters prove satisfactory concurrence with the theoretical prediction from DFT. The scaled vibrational frequencies seem to coincide with the experimentally observed values with acceptable deviations. The theoretical spectrograms have been constructed and compared with the experimental FT-Raman and FT-IR spectra. The calculated Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies show that charge transfer occurs in the molecule. The first order hyperpolarizability ?total of this molecular system and related properties (?, ?, ? and ??) are calculated using DFT/B3LYP/6-31G(d,p) and 6-311++G(d,p) basis set based on the finite-field approach. Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Thermodynamic properties like entropy, heat capacity and zero-point energy have been calculated for the molecule. PMID:24412793

Prabhaharan, M; Prabakaran, A R; Gunasekaran, S; Srinivasan, S

2014-04-01

34

Calculation of ground vibration spectra from heavy military vehicles  

NASA Astrophysics Data System (ADS)

The demand for reliable autonomous systems capable to detect and identify heavy military vehicles becomes an important issue for UN peacekeeping forces in the current delicate political climate. A promising method of detection and identification is the one using the information extracted from ground vibration spectra generated by heavy military vehicles, often termed as their seismic signatures. This paper presents the results of the theoretical investigation of ground vibration spectra generated by heavy military vehicles, such as tanks and armed personnel carriers. A simple quarter car model is considered to identify the resulting dynamic forces applied from a vehicle to the ground. Then the obtained analytical expressions for vehicle dynamic forces are used for calculations of generated ground vibrations, predominantly Rayleigh surface waves, using Green's function method. A comparison of the obtained theoretical results with the published experimental data shows that analytical techniques based on the simplified quarter car vehicle model are capable of producing ground vibration spectra of heavy military vehicles that reproduce basic properties of experimental spectra.

Krylov, V. V.; Pickup, S.; McNuff, J.

2010-07-01

35

Vibration Reduction of a Harmonically Excited Beam with One-sided Spring Using Sliding Computed Torque Control  

Microsoft Academic Search

Vibration reduction of a harmonically excited multi Degree of Freedom (DOF) beam system with a local nonlinearity represented by a one-sided spring is considered. The linear beam system is modeled with a 3-DOF model which is obtained by applying a component mode synthesis method on the linear finite element model of the beam system. The low frequency response of the

M. F. Heertjes; M. J. G. van de Molengraft; J. J. Kok; D. H. van Campen

1997-01-01

36

Analysis of vibrational spectra of L-alanylglycine based on density functional theory calculations  

NASA Astrophysics Data System (ADS)

FT Raman and IR spectra of the crystallized biologically active molecule, L-alanylglycine ( L-Ala-Gly) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies of L-Ala-Gly have been investigated with the help of B3LYP density functional theory (DFT) method. The calculated molecular geometry has been compared with the experimental data. 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 geometry shows the non-planarity of the peptide group of the molecule. Potential energy surface (PES) scan studies has also been carried out by ab initio calculations with B3LYP/6-311+G** basis set. The red shifting of NH 3+ stretching wavenumber indicates the formation of N sbnd H⋯O hydrogen bonding. The change in electron density (ED) in the ? * antibonding orbitals and E2 energies have been calculated by natural bond orbital analysis (NBO) using DFT method. The NBO analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule.

Padmaja, L.; Ravikumar, C.; James, C.; Jayakumar, V. S.; Hubert Joe, I.

2008-11-01

37

Calculation of the vibrational spectra of betaine hydrochloride  

NASA Astrophysics Data System (ADS)

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

Szafran, Miroslaw; Koput, Jacek

1997-02-01

38

Vibrational and thermal effects on the dipole polarizability of methane and carbon tetrachloride from vibrational structure calculations  

NASA Astrophysics Data System (ADS)

We present a theoretical study of vibrational and thermal effects on the dipole polarizability of methane and carbon tetrachloride. Using a fourth order Taylor expansion in rectilinear normal coordinates of the potential and property surfaces we solve the vibrational problem using vibrational structure theory, e.g., through vibrational self-consistent-field or vibrational configuration-interaction theory. For each vibrational state we calculate in addition the vibrational state average polarizability. Constructing the vibrational partition function by "brute force" allows for prediction of thermal effects on the dipole polarizability. The method is not restricted in any way to polarizabilities nor to the specific representation of the potential and property surfaces employed in this work. Any molecular property with a suitable normal coordinate representation may be considered. We discuss the performance of vibrational self-consistent field as compared to vibrational configuration interaction and study in detail the convergence of the former method with respect to the number of vibrational states included in the thermal averaging. Based on calculations including up to 170 000 vibrational self-consistent-field states we present thermal effects on the dipole polarizability of methane and carbon tetrachloride in the temperature ranges 0-1100 and 0-500K, respectively. The predicted thermal effect on the dipole polarizability of methane is found to be ˜0.8% which compare well with previous experimental measurements.

Kongsted, Jacob; Christiansen, Ove

2007-10-01

39

Harmonic vibrational frequencies and infrared intensities from analytic fourth-order many-body perturbation theory gradients  

NASA Astrophysics Data System (ADS)

Recently developed fourth-order many-body perturbation theory [MBPT(4)] analytic gradient techniques are applied to a study of the harmonic vibrational frequencies and infrared intensities of prototype small polyatomic molecules. Results are presented for the complete fourth-order model as well as for the SDQ-MBPT(4) scheme, which neglects the contribution of triple excitations. These results are also compared to frequencies and intensities obtained at both higher and lower levels of theory. Differences between the fourth-order results and those obtained with the infinite order coupled-cluster (CC) counterparts of SDQ-MBPT(4) and MBPT(4) [CCSD and CC models including triple excitations, the latter approximated here by CCSDT-1 and the UCC(4) model] are found to be negligible for all bending modes and stretches involving single bonds. However, the infinite order effects included in CC models are important for describing stretching modes of multiple bonds. Therefore, iterative CC calculations are needed to accurately characterize these regions of the potential surface.

Stanton, John F.; Watts, John D.; Bartlett, Rodney J.

1991-01-01

40

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

NASA Technical Reports Server (NTRS)

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

Jarzembski, Maurice A.; Srivastava, Vandana

1999-01-01

41

Harmonic power flow calculations for a large power system with multiple nonlinear loads using decoupled approach  

Microsoft Academic Search

Power flow calculation is normally carried out for fundamental frequency. Due to the extensive use of nonlinear loads, harmonic frequencies are present and need to be also considered. Unfortunately, unavoidable complexity and heavy computation burden are often encountered by involving nonlinear loads into the calculation. Multiple nonlinear loads typically employed in the real system will further weigh the computation down.

A. Ulinuha; M. A. S. Masoum; S. M. Islam

2007-01-01

42

Crystal and molecular structure, conformational, vibrational properties and DFT calculations of melaminium bis (hydrogen oxalate)  

NASA Astrophysics Data System (ADS)

Single crystals of melaminium bis (hydrogen oxalate) (MOX) were grown by slow evaporation method. X-ray powder diffraction analysis indicates that MOX crystallizes in monoclinic system (space group C2/c) and the calculated lattice constants are a = 20.075 ± 0.123 ?, b = 8.477 ± 0.045 ?, c = 6.983 ± 0.015, ? = ? 90° and ? = 102.6 ± 0.33°. Thermal analysis confirms that MOX is thermally stable up to 250 °C. A detailed interpretation of the FT-IR, FT-Raman and NMR spectra were reported. The equilibrium geometry, bonding features, and harmonic vibrational frequencies have been investigated with the help of PM6, HF and DFT/B3LYP methods. The potential energy curve shows that MOX molecule has two stable structures and the computational results diagnose that Rot I is the most stable conformer. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge-Invariant Atomic Orbital (GIAO) method. Stability of the molecule, arising from hyperconjugative interactions and charge delocalization, has been analyzed using Natural Bond Orbital (NBO) analysis. The electronic properties, such as HOMO and LUMO energies, were calculated by Time-Dependent DFT (TD-DFT) approach. To estimate chemical reactivity of the molecule, the molecular electrostatic potential (MEP) surface map is calculated for the optimized geometry of the molecule.

Sangeetha, V.; Govindarajan, M.; Kanagathara, N.; Gunasekaran, S.; Rajakumar, P. R.; Anbalagan, G.

2014-06-01

43

HOTB: High precision parallel code for calculation of four-particle harmonic oscillator transformation brackets  

NASA Astrophysics Data System (ADS)

This new version of the HOTB program for calculation of the three and four particle harmonic oscillator transformation brackets provides some enhancements and corrections to the earlier version (Germanas et al., 2010) [1]. In particular, new version allows calculations of harmonic oscillator transformation brackets be performed in parallel using MPI parallel communication standard. Moreover, higher precision of intermediate calculations using GNU Quadruple Precision and arbitrary precision library FMLib [2] is done. A package of Fortran code is presented. Calculation time of large matrices can be significantly reduced using effective parallel code. Use of Higher Precision methods in intermediate calculations increases the stability of algorithms and extends the validity of used algorithms for larger input values. Catalogue identifier: AEFQ_v4_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEFQ_v4_0.html Program obtainable from: CPC Program Library, Queen’s University of Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 Number of lines in programs, including test data, etc.: 1711 Number of bytes in distributed programs, including test data, etc.: 11667 Distribution format: tar.gz Program language used: FORTRAN 90 with MPI extensions for parallelism Computer: Any computer with FORTRAN 90 compiler Operating system: Windows, Linux, FreeBSD, True64 Unix Has the code been vectorized of parallelized?: Yes, parallelism using MPI extensions. Number of CPUs used: up to 999 RAM(per CPU core): Depending on allocated binomial and trinomial matrices and use of precision; at least 500 MB Catalogue identifier of previous version: AEFQ_v1_0 Journal reference of previous version: Comput. Phys. Comm. 181, Issue 2, (2010) 420-425 Does the new version supersede the previous version? Yes Nature of problem: Calculation of matrices of three-particle harmonic oscillator brackets (3HOB) and four-particle harmonic oscillator brackets (4HOB) in a more effective way, which allows us to calculate matrix of the brackets up to a few hundred times more rapidly and more accurate than in a previous version. Solution method: Using external parallelization libraries and mutable precision we created a pack of numerical codes based on the methods of compact expressions of the three and four-particle harmonics oscillator brackets 3HOB, 4HOB, presented in [3]. Restrictions: For double precision version calculations can be done up to harmonic oscillator (HO) energy quanta e=28. For quadruple precision mantissa is equal to approximately 34 decimal digits, therefore calculations can be done up to HO energy quanta to e=52. Running time: The running time depends on the harmonic oscillator energy quanta, cluster size and the precision of intermediate calculations. More information on Table 1 for 3HOB and Table 2 for 4HOB. Reasons for a new version: The new program version expands the limits of harmonic oscillator energy quanta and gives shorter calculation time. Extend the limits of calculation of HOB First version was able to produce harmonic oscillator transformation brackets for three and four particles if E?HO energy quanta. With this version of our program, if quadruple or arbitrary precision functions are being used, it is possible to calculate three and four particle harmonic oscillator transformation brackets for greater values of energy and momenta, while sustaining tolerable margin of error. Calculation time As the code of previous version of program was redone using parallelism paradigma, it is now possible to reduce the calculation time of transformation matrices significantly, depending on the size of computing cluster, as the dimensions of matrices are growing very rapidly according to the energy and momenta values. subroutinematrix_4HOB_dimensionCalculates the dimension of 4HOB matrix. subroutinematrix_3HOB_dimensionCalculates the dimension of 3HOB matrix, subroutinematrix_3HOBCalculates the global state array which is used in parallel calculation of 3HOB matrix. subroutinematrix_4HOBCalculates the global sta

Stepšys, A.; Mickevicius, S.; Germanas, D.; Kalinauskas, R. K.

2014-11-01

44

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

PubMed

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

Park, G Barratt

2014-10-01

45

Quantum chemical calculations of vibrational spectra of para-ethylbenzenesulfonic acid  

NASA Astrophysics Data System (ADS)

Quantum chemical calculations of vibrational spectra of para-ethylbenzenesulfonic acid have been conducted by means of a non-empirical SCF MO LCAO method with the use of the 6-31G( d) basis set. Calculated IR and Raman frequencies are assigned to vibrations of specific atomic groups. It is shown that para-ethylbenzenesulfonic acid can serve as a reasonable quantum chemical model in calculations of vibrational spectra for polystyrene sulfonic resins of various degrees of hydration.

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

2010-05-01

46

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

NASA Astrophysics Data System (ADS)

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 4000-400 cm-1 and 3600-50 cm-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.

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

2012-11-01

47

Molecular structure, normal coordinate analysis, harmonic vibrational frequencies, NBO, HOMO-LUMO analysis and detonation properties of (S)-2-(2-oxopyrrolidin-1-yl) butanamide by density functional methods  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) computations have become an efficient tool in the prediction of molecular structure, harmonic force fields, vibrational wave numbers as well as the IR and Raman intensities of pharmaceutically important molecule. In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis and detonation properties of (S)-2-(2-oxopyrrolidin-1-yl) butanamide. The solid phase FT-IR and FT-Raman spectra of (S)-2-(2-oxopyrrolidin-1-yl) butanamide were recorded in the region 4000-450 cm-1 and 4000-50 cm-1 respectively. Harmonic frequencies of this compound were determined and analyzed by DFT utilizing 6-31G(d,p), 6-31+G(d,p) basis sets. 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 calculated infrared and Raman spectra of the title compounds were also stimulated utilizing the scaled force fields and the computed dipole derivatives for IR intensities and polarizability derivatives for Raman intensities. The change in electron density (ED) in the ?* and ?* antibonding orbital's 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. Heat of formation (HOF) and calculated density were estimated to evaluate detonation properties using Kamlet-Jacobs equations. The linear polarizability (?) and the first order hyperpolarizability (?) values of the investigated molecule have been computed using DFT calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The observed and calculated wave numbers are found to be in good agreement. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated.

Renuga, S.; Muthu, S.

2014-01-01

48

Molecular structure, normal coordinate analysis, harmonic vibrational frequencies, NBO, HOMO-LUMO analysis and detonation properties of (S)-2-(2-oxopyrrolidin-1-yl) butanamide by density functional methods.  

PubMed

Density functional theory (DFT) computations have become an efficient tool in the prediction of molecular structure, harmonic force fields, vibrational wave numbers as well as the IR and Raman intensities of pharmaceutically important molecule. In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis and detonation properties of (S)-2-(2-oxopyrrolidin-1-yl) butanamide. The solid phase FT-IR and FT-Raman spectra of (S)-2-(2-oxopyrrolidin-1-yl) butanamide were recorded in the region 4000-450 cm(-1) and 4000-50 cm(-1) respectively. Harmonic frequencies of this compound were determined and analyzed by DFT utilizing 6-31G(d,p), 6-31+G(d,p) basis sets. 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 calculated infrared and Raman spectra of the title compounds were also stimulated utilizing the scaled force fields and the computed dipole derivatives for IR intensities and polarizability derivatives for Raman intensities. The change in electron density (ED) in the ?(*) and ?(*) antibonding orbital's 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. Heat of formation (HOF) and calculated density were estimated to evaluate detonation properties using Kamlet-Jacobs equations. The linear polarizability (?) and the first order hyperpolarizability (?) values of the investigated molecule have been computed using DFT calculations. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The observed and calculated wave numbers are found to be in good agreement. On the basis of vibrational analyses, the thermodynamic properties of title compound at different temperatures have been calculated. PMID:24096066

Renuga, S; Muthu, S

2014-01-24

49

First Principles Calculation of Terahertz Vibrational Modes of a Disaccharide Monohydrate Crystal of Lactose  

NASA Astrophysics Data System (ADS)

First-principles calculations of the crystalline vibrations of a lactose monohydrate crystal in the terahertz (THz) region were performed using periodic density functional theory calculations. The calculated vibrational modes in the THz region were derived from group motions with different sizes: molecules of lactose and crystal water, pyranose rings, and intramolecular frames. The intermolecular modes with large vibrational amplitude of lactose of 17.5-100.6 cm-1 and of crystal-water of 136.1-237.7 cm-1 were clearly separated. This article especially refers to the intermolecular vibrational modes of crystal water with the THz absorption, which provide detectable spectral features of hydrated crystals.

Saito, Shigeki; Inerbaev, Talgat M.; Mizuseki, Hiroshi; Igarashi, Nobuaki; Note, Ryunosuke; Kawazoe, Yoshiyuki

2006-11-01

50

Time averaging the semiclassical initial value representation for the calculation of vibrational energy levels  

E-print Network

, particularly so for the calculation of spectral densities from which vibrational energy levels canTime averaging the semiclassical initial value representation for the calculation of vibrational energy levels Alexey L. Kaledin and William H. Millera) Department of Chemistry and Kenneth S. Pitzer

Miller, William H.

51

A structural and vibrational study on the first condensed borosulfate K5[B(SO4)4] by using the FTIR-Raman spectra and DFT calculations  

NASA Astrophysics Data System (ADS)

The first borosulfate, K5[B(SO4)4] (recently synthesized by Henning A. Höppe, Karolina Kazmierczak, Michael Daub, Katharina Förg, Franziska Fuchs, Harald Hillebrecht, 2012) was characterized by infrared and Raman spectroscopies. Density functional theory (DFT) calculations were used to study the structure and vibrational properties of the compound. Employing the B3P86 and B3LYP levels of theory, the molecular structures of the compound were theoretically determined in gas phase and the harmonic vibrational frequencies were evaluated at the same levels. The calculated harmonic vibrational frequencies for the borosulfate compound are consistent with the experimental IR and Raman spectra. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by sulfate groups of this compound as ligands with C3v and C2v symmetries. A complete assignment of all the observed bands in the IR and Raman spectra for K5[B(SO4)4] was performed. Here, the infrared and Raman spectra of K5[B(SO4)4] were interpreted, discussed and completely assigned. The nature of the Ksbnd O, Ksbnd S, Bsbnd O, and Ssbnd O bonds and the topological properties of the compound were investigated and analyzed by means of Natural Bond Order (NBO) and Bader's Atoms in Molecules theory (AIM), respectively.

Höppe, Henning Alfred; Kazmierczak, Karolina; Romano, Elida; Brandán, Silvia Antonia

2013-04-01

52

Structural, electronic, elastic, thermodynamic and vibration properties of TbN compound from first principles calculations  

NASA Astrophysics Data System (ADS)

We have predicted structural, electronic, elastic, thermodynamic and vibration characteristics of TbN, using density functional theory within generalized-gradient (GGA) apraximation. For the total energy calculation we have used the projected augmented plane-wave (PAW) implementation of the Vienna Ab initio Simulation Package (VASP). We have used to examine structure parameter in eight different structures such as in NaCl (B1), CsCl (B2), ZB (B3), Tetragonal (L10), WC (Bh), NiAs (B8), PbO (B10) and Wurtzite (B4). We have performed the thermodynamics properties for TbN by using quasi-harmonic Debye model. We have, also, predicted the temperature and pressure variation of the volume, bulk modulus, thermal expansion coefficient, heat capacities and Debye temperatures in a wide pressure (0-130 GPa) and temperature ranges (0-2000 K). Furthermore, the band structure, phonon dispersion curves and corresponding density of states are computed. Our results are compared to other theoretical and experimental works, and excellent agreement is obtained.

Ciftci, Y. O.; Ozayman, M.; Surucu, G.; Colakoglu, K.; Deligoz, E.

2012-03-01

53

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

54

On the Dynamics of a Harmonic Oscillator Undergoing Impacts with a Vibrating Platform  

Microsoft Academic Search

This paper deals with a model for repeated impacts of a massattached to a spring with a massive, sinusoidally vibrating table. Thismodel has been studied in an attempt to understand the cantilever-sampledynamics in atomic force microscopy. In this work, we have shown thatfor some values of the frequency of the vibrating table, there arecountably many orbits of arbitrarily long periods

S. Salapaka; M. Dahleh; I. Mezi?

2001-01-01

55

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

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

2013-02-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

57

Structural conformations, tautomerization and vibrational spectral study of 6-amino-1-methylpurine with density functional theoretical calculations  

NASA Astrophysics Data System (ADS)

The FT-IR and FT-Raman spectra of 6-amino-1-methylpurine (AMP) have been recorded in the region 4000-400 cm-1 and 3500-50 cm-1 respectively. The optimized geometry, frequency and intensity of the vibrational bands of AMP have been obtained by DFT level of theory using B3LYP method with 6-311++G(d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. Purines, including substituted purines and their tautomers, are the most widely occurring nitrogen-containing heterocyclic in nature. Purines and pyrimidines make up the two groups of nitrogenous bases, including the two groups of nucleotide bases. Two of the four deoxyribonucleotides and two of the four ribonucleotides, the respective building-blocks of DNA and RNA, are purines. The calculated vibrational values are in good agreement when they are compared with IR and Raman experimental data. Amine-imine tautomerism of 6-amino-1-methyl purine is studied in detail. In agreement with experimental results, it was found that imine tautomer is more stable than amine tautomer.

Arivazhagan, M.; Kavitha, R.; Subhasini, V. P.

2014-07-01

58

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

SciTech Connect

We apply the adiabatic switching (AS) method to determine the polyatomic classical motions that correspond to selected vibrational quantum states on multidimensional, anharmonic potential energy surfaces, and use these semiclassically quantized motions as initial conditions for quasiclassical trajectory (QCT) calculations of state-to-state reaction dynamics. Specifically, we calculate the classical motion corresponding to the quantum mechanical zero-point vibration of deuterated methane, CD{sub 4}, and run QCT calculations on the H+CD{sub 4}{r_arrow}HD({ital v}{prime},{ital j}{prime})+CD{sub 3} reaction. The distribution of CD{sub 4} vibrational zero-point energy (ZPE) associated with the AS-sampled motions is compared with that from normal-mode-sampled motions. The spread of total zero-point energy in the AS calculations is much narrower than with normal-mode sampling, and the ZPE`s are appropriately shifted to lower energy due to anharmonic effects. Reverse adiabatic switching is used as an indirect check of the quantum numbers of the adiabatically sampled motion, but numerical limitations made this test inconclusive. The AS method thus appears to be superior to normal-mode sampling, but this superiority cannot be demonstrated conclusively for the fully anharmonic CD{sub 4} potential. However, the AS method is shown to perform very well for transformation from one CD{sub 4} harmonic potential to another and for transformation from an harmonic to an anharmonic, but decoupled potential in which CD{sub 4} is described by Morse oscillators. Evidence is presented that suggests the AS calculations are limited by numerical inaccuracies or intrinsic features of the potential energy surface, both of which are unavoidable. H+CD{sub 4}{r_arrow}HD({ital v}{prime},{ital j}{prime})+CD{sub 3} QCT calculations of state-to-state dynamics using CD{sub 4} with no ZPE, the ZPE from AS sampling, and the ZPE from normal-mode sampling are reported and compared.

Huang, J.; Valentini, J.J. [Department of Chemistry, Columbia University, New York, New York 10027 (United States)] [Department of Chemistry, Columbia University, New York, New York 10027 (United States); Muckerman, J.T. [Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

1995-04-08

59

Calculation of ground state energy of harmonically confined two dipolar fermions  

E-print Network

We calculate the ground state energies of a system of two dipolar fermions trapped in a harmonic oscillator potential. The dipoles are assumed to be aligned parallel to each other. We perform the calculations of ground state energy as a function of strength of interaction between two fermions by employing variational method with Hylleraas-like explicitly correlated wave function. Furthermore, we perform calculations of ground state energy within Hartree-Fock approximation and the magnitude of correlation energy is estimated by subtracting these results from the corresponding wave function based results. We also carry out calculations of ground state energies within the realm of density functional theory by using recently reported expressions for exchange and correlation energies under local density approximation. By comparing correlated wave function based results with those obtained using density functional theory approach we examine the role of fermion-fermion correlation and assess the accuracy of local de...

Das, Amit K

2014-01-01

60

Calculation of vibrational spectra for complexes of alkali-metal and magnesium cations with acetonitrile molecules  

NASA Astrophysics Data System (ADS)

Quantum-chemical calculations of the optimum geometries and vibrational spectra for complexes of acetonitrile (AN) with Li+, Na+, K+, and Mg2+ cations were performed at the B3LYP/6-31+G(d, p) level. The best fit between the calculated and experimental frequency shifts for intramolecular vibrations of coordinated AN as compared to those of uncoordinated AN was observed for coordination number n = 4 for Li+, Na+, and K+ and n = 6 for Mg2+. It was found that the ion-molecule vibrational frequency (cation-solvent) was most sensitive to the number of molecules in the solvation shell.

Mikhailov, G. P.

2013-03-01

61

Calculation of vibrational relaxation times in multi-component excitable gases  

NASA Astrophysics Data System (ADS)

In the research field of acoustic propagation in excitable gases, one of the most critical parameters is the vibrational relaxation time, which determines the frequency of the acoustic dispersion step or the absorption maximum. In this paper, the vibrational relaxation equations given by Tanczos [J. Chem. Phys. 25, 439 (1956)] have been applied to calculate the vibrational multi-relaxation times in multi-component gases. The eigenvalues of the energy-transition-rate matrix are proven to be the reciprocals of the multi-relaxation times. Comparisons demonstrate that our relaxation frequencies calculated for various gas compositions, including carbon dioxide, methane, chlorine, nitrogen, and oxygen, agree with the experimental data.

Zhang, Ke-Sheng; Ou, Weihua; Jiang, Xueqin; Long, Fei; Hu, Mingzhe

2014-10-01

62

Molecular structure and vibrational investigation of benzenesulfonic acid methyl ester using DFT (LSDA, B3LYP, B3PW91 and MPW1PW91) theory calculations  

Microsoft Academic Search

The FT-Raman and FT-IR spectra for benzenesulfonic acid methyl ester (BSAME) have been recorded in the region 4000–100cm?1 and compared with the harmonic vibrational frequencies calculated using DFT (LSDA, B3LYP, B3PW91 and MPW1PW91) method by employing 6-311G (d, p) basis set with appropriate scale factors. IR intensities and Raman activities are also calculated by DFT (LSDA, B3LYP, B3PW91 and MPW1PW91)

P. David Suresh Babu; S. Periandy; S. Mohan; S. Ramalingam; B. G. Jayaprakash

2011-01-01

63

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

NASA Astrophysics Data System (ADS)

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

Tsogbayar, Ts; Horbatsch, M.

2014-06-01

64

First-principles calculation of vibrational Raman spectra of tetrahedral amorphous carbon  

NASA Astrophysics Data System (ADS)

The nonresonant vibrational Raman spectra of tetrahedral amorphous carbon are calculated from first principles. The structural model was generated using Car-Parinello molecular dynamics, the vibrational modes are determined using the linear response approach and Raman tensors are calculated using the finite electric field method. Our theoretical visible and reduced Raman spectra show an overall good agreement with experimental spectra, and better than previous calculated results. The analysis in terms of atomic vibrations shows that the Raman spectrum mainly comes from sp 2 contribution, G peak is due to the stretching vibration of any pair of sp 2 atoms and only a small sp 3 contribution can be noticed. The differences between peak intensities of reduced theoretical and experimental results mainly come from defects and the high sp 3 content in our simulated structure.

Niu, Li; Zhu, Jiaqi; Gao, Wei; Liu, Aiping; Han, Xiao; Du, Shanyi

2008-10-01

65

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

66

Application of a Spherical Harmonics Expansion Approach for Calculating Ligand Density Distributions around Proteins.  

PubMed

Protein-ligand interactions are central to many biological applications, including molecular recognition, protein formulations, and bioseparations. Complex, multisite ligands can have affinities for different locations on a protein's surface, depending on the chemical and topographical complementarity. We employ an approach based on the spherical harmonic expansion to calculate spatially resolved three-dimensional atomic density profiles of water and ligands in the vicinity of macromolecules. To illustrate the approach, we first study the hydration of model C180 buckyball solutes, with nonspherical patterns of hydrophobicity/-philicity on their surface. We extend the approach to calculate density profiles of increasingly complex ligands and their constituent groups around a protein (ubiquitin) in aqueous solution. Analysis of density profiles provides information about the binding face of the protein and the preferred orientations of ligands on the binding surface. Our results highlight that the spherical harmonic expansion based approach is easy to implement and efficient for calculation and visualization of three-dimensional density profiles around spherically nonsymmetric and topographically and chemically complex solutes. PMID:25198149

Parimal, Siddharth; Cramer, Steven M; Garde, Shekhar

2014-11-20

67

Loss Calculation of Induction Motors Considering Harmonic Electromagnetic Fields in Stator and Rotor  

NASA Astrophysics Data System (ADS)

A method of loss calculation for induction motors is proposed. The combined 3D-2D time stepping finite element analysis is carried out to obtain the copper loss and the time-variation of the magnetic field in the motor. The iron loss is calculated approximately considering the time-variation of the magnetic field direction and the minor hysteresis loops caused by the time-harmonic fields using practical computer resources. The proposed method is applied to 4 types of induction motors, which are the solid rotor induction motors with/without slot and the cage induction motors with/without skew. The measured and the calculated total losses and the iron losses agree well in all cases. The differences of the loss distributions of each motor are also compared and investigated.

Yamazaki, Katsumi

68

DFT calculation and vibrational spectroscopic studies of 2-(tert-butoxycarbonyl (Boc) -amino)-5-bromopyridine  

NASA Astrophysics Data System (ADS)

The molecular structure of 2-(tert-butoxycarbonyl (Boc) -amino)-5-bromopyridine (BABP) was optimized by the DFT/B3LYP method with 6-311G (d,p), 6-311++G (d,p) and cc-pVTZ basis sets using the Gaussian 09 program. The most stable optimized structure of the molecule was predicted by the DFT/B3LYP method with cc-pVTZ basis set. The vibrational frequencies, Mulliken atomic charge distribution, frontier molecular orbitals and thermodynamical parameters were calculated. These calculations were done at the ground state energy level of BABP without applying any constraint on the potential energy surface. The vibrational spectra were experimentally recorded using Fourier Transform-Infrared (FT-IR) and micro-Raman spectrometer. The computed vibrational frequencies were scaled by scale factors to yield a good agreement with observed experimental vibrational frequencies. The complete theoretically calculated and experimentally observed vibrational frequencies were assigned on the basis of Potential Energy Distribution (PED) calculation using the VEDA 4.0 program. The vibrational modes assignments were performed by using the animation option of GaussView 05 graphical interface for Gaussian program. The Mulliken atomic charge distribution was calculated for BABP molecule. The molecular reactivity and stability of BABP were also studied by frontier molecular orbitals (FMOs) analysis.

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

2014-08-01

69

The assignment of the vibrations of substituted mercaptotetrazoles based on quantum chemical calculations  

NASA Astrophysics Data System (ADS)

We studied four substituted mercaptotetrazoles using IR- and Raman-spectroscopy on the bulk substance and surface enhanced Raman spectroscopy (SERS) on a silver colloid. Semiempirical and ab initio calculations with various basis sets were performed to establish an assignment of the experimentally observed bands to the calculated ones. We found a satisfactory agreement between the calculated and observed frequencies of CH/CC-vibrations in the phenyl ring and encountered problems with the tetrazole ring vibrations. The PM3 hamiltonian failed for the SH group.

Sägmüller, Bernd; Freunscht, Peter; Schneider, Siegfried

1999-05-01

70

Pyridine N-oxide/trichloroacetic acid complex in acetonitrile: FTIR spectra, anharmonic calculations and computations of 1-3D potential surfaces of O-H vibrations.  

PubMed

FTIR spectra of pyridine N-oxide and trichloroacetic acid H-bonded complex in acetonitrile were studied at 20 and 50°C. The calculations of equilibrium configurations of the complex and their IR spectra in harmonic- and anharmonic approximations were carried out at the level of B3LYP/cc-pVTZ/PCM. However both approximations turned out to be incompetent determining the frequency of the O-? stretching vibration. In order to reveal the causes of essential discrepancies between calculated and experimental data one-, two- and three-dimensional potential energy surfaces (PES) of the O-H…O bridge proton motion in the frame of fixed other atoms in the complex were calculated. The frequencies of O-H…O stretching and bending vibrations were calculated by numerical solution of the Schrödinger equation. It is shown that only the approach of proton motion on the 3D PES allows obtaining a good agreement between the calculated and the experimental values of the frequencies of the ?-? stretching vibrations. PMID:24373980

Pitsevich, G; Malevich, A; Doroshenko, I; Kozlovskaya, E; Pogorelov, V; Sablinskas, V; Balevicius, V

2014-01-01

71

Examination of super-harmonics in a multi-degree of freedom nonlinear vibration isolation system: Refined models and comparison with measurements  

NASA Astrophysics Data System (ADS)

A multi-degree of freedom vibration isolation experiment consisting of a powertrain, three powertrain mounts including a dynamic load sensing hydraulic mount, a sub-frame, and 4 bushings is examined in both time and frequency domains. Since the hydraulic mount exhibits nonlinear phenomena, super-harmonics are observed in motion, pressure and interfacial force measurements when the system is sinusoidally excited. Refined indirect force estimation methods are proposed with a focus on the super-harmonics. This includes the development of a quasi-linear fluid system model with embedded spectrally varying and amplitude-sensitive parameters. The reverse path spectral method is employed using the measured relative motion and upper chamber pressure in the nonlinear hydraulic mount. The relevant transfer functions (with effective parameters for both rubber and hydraulic paths) are used to estimate the interfacial forces. Up to six harmonics of the fundamental excitation frequency are examined, and the contribution of each path is clarified. The proposed quasi-linear fluid system model including super-harmonics extends prior work on indirect force estimation methods and successfully predicts the interfacial forces in the multi-degree of freedom vibration isolation system. The quasi-linear fluid system model, however, seems to be inadequate in estimating the sub-harmonic responses.

Yoon, Jong-Yun; Singh, Rajendra

2014-10-01

72

Transformation of potential energy surfaces for estimating isotopic shifts in anharmonic vibrational frequency calculations  

NASA Astrophysics Data System (ADS)

A transformation of potential energy surfaces (PES) being represented by multi-mode expansions is introduced, which allows for the calculation of anharmonic vibrational spectra of any isotopologue from a single PES. This simplifies the analysis of infrared spectra due to significant CPU-time savings. An investigation of remaining deviations due to truncations and the so-called multi-level approximation is provided. The importance of vibrational-rotational couplings for small molecules is discussed in detail. In addition, an analysis is proposed, which provides information about the quality of the transformation prior to its execution. Benchmark calculations are provided for a set of small molecules.

Meier, Patrick; Oschetzki, Dominik; Berger, Robert; Rauhut, Guntram

2014-05-01

73

Calculation of the vibrational spectra of betaine hydrochloride  

Microsoft Academic Search

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

Miroslaw Szafran; Jacek Koput

1997-01-01

74

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

NASA Astrophysics Data System (ADS)

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

Kwak, Moon K.; Yang, Dong-Ho

2013-09-01

75

Vibrational state-to-state calculations of H(+) + O2 charge transfer collisions  

Microsoft Academic Search

Vibrational excitation and vibronic charge transfer in the H(+) + O2 collision at E(CM) = 23 eV are theoretically investigated. The vibronic semiclassical (VSC) and the quantal infinite order sudden (QIOS) descriptions of the quantum dynamics of nondiabatic vibronic processes are directly compared. VSC calculations of differential cross section for such processes are reported, which take into account both the

M. Sizun; D. Grimbert; V. Sidis; M. Baer

1992-01-01

76

A new method to calculate the vibrational stress of rotating blades  

Microsoft Academic Search

A new reverse educing method (REM) is presented to estimate the vibrational stress on rotating aeroengine blades from the actual fracture section. This method does not conform to the traditional calculating method, but involves the reverse solution idea. The value of the crack propagation ratio da\\/dN can be obtained from the actual fracture section of the blade, and then the

Hai-Yan Li; Xue-Ren Zhang; Xiao-Jun Yan; Jing-Xu Nie

2001-01-01

77

Density functional theory based calculations of the vibrational properties of chlorophyll-a  

E-print Network

Density functional theory based calculations of the vibrational properties of chlorophyll-a Ruili in revised form 8 March 2007; accepted 13 March 2007 Available online 23 March 2007 Abstract Chlorophyll organisms, such as plants algae and cyanobacteria. To study the chlorophyll-a species at the heart

Hastings, Gary

78

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

79

Studies of the molecular geometry, vibrational spectra, Frontier molecular orbital, nonlinear optical and thermodynamics properties of Aceclofenac by quantum chemical calculations  

NASA Astrophysics Data System (ADS)

The solid phase FT-IR and FT-Raman spectra of 2-[2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetyl] oxyacetic acid (Aceclofenac) have been recorded in the region 4000-400 and 4000-100 cm-1 respectively. The optimized molecular geometry and fundamental vibrational frequencies are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method and a comparative study between Hartree Fork (HF) method 6-311++G(d,p) level basis set. The calculated harmonic vibrational frequencies were scaled and have been compared with experimental by obtained FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The time dependent DFT method employed to study its absorption energy and oscillator strength. The linear polarizability (?) and the first order hyper polarizability (?) values of the investigated molecule have been computed. The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MESP) were also performed. Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

Suresh, S.; Gunasekaran, S.; Srinivasan, S.

80

Studies of the molecular geometry, vibrational spectra, frontier molecular orbital, nonlinear optical and thermodynamics properties of aceclofenac by quantum chemical calculations.  

PubMed

The solid phase FT-IR and FT-Raman spectra of 2-[2-[2-[(2,6-dichlorophenyl)amino]phenyl]acetyl] oxyacetic acid (Aceclofenac) have been recorded in the region 4000-400 and 4000-100 cm(-1) respectively. The optimized molecular geometry and fundamental vibrational frequencies are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method and a comparative study between Hartree Fork (HF) method 6-311++G(d,p) level basis set. The calculated harmonic vibrational frequencies were scaled and have been compared with experimental by obtained FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The time dependent DFT method employed to study its absorption energy and oscillator strength. The linear polarizability (?) and the first order hyper polarizability (?) values of the investigated molecule have been computed. The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MESP) were also performed. Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. PMID:24556133

Suresh, S; Gunasekaran, S; Srinivasan, S

2014-05-01

81

Harmonic Convergence  

NSDL National Science Digital Library

Harmonic convergence refers to a day back in 1987 where there was a particular planetary alignment. New Agers went crazy over the event, and if you want to get a taste of what it was like, enter harmonic convergence into your favorite Internet search engine and sit back and enjoy. This chapter adds to the previous discussion of resonance by expanding the list of vibrating things to metal rods and columns of air.

Robertson, William C.

2003-01-01

82

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

PubMed

Anharmonic vibrational frequencies for the Raman-active (A(1g)) and the IR-active (A(2u)) 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. PMID:18715080

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

2008-08-14

83

The Calculation of Harmonic Production in Thermionic Valves with Resistive Loads  

Microsoft Academic Search

Formulas are obtained for the amplitudes of harmonic components and the direct-current change in the anode current of thermionic valves operating with resistive loads. These expressions for components up to the sixth harmonic are given in terms of points taken from the load line on the anode-voltage-anode-current characteristics at equally spaced intervals of grid voltage.

D. C. Espley

1933-01-01

84

Potential energy surfaces for vibrational structure calculations from a multiresolution adaptive density-guided approach: implementation and test calculations.  

PubMed

A multiresolution procedure to construct potential energy surfaces (PESs) for use in vibrational structure calculations is developed in the framework of the adaptive density-guided approach. The implementation of the method allows the construction of hybrid PESs with different mode-coupling terms calculated with a variety of combinations of electronic structure methods and basis sets. Furthermore, the procedure allows the construction of hybrid PESs that incorporate a variety of contributions and corrections to the electronic energy, such as infinite basis set extrapolation and core correlation effects. A full account of the procedure is given together with a rather large set of benchmark calculations on a set of 20 small molecules, from diatomics to tetratomics. PMID:19583195

Sparta, Manuel; Høyvik, Ida-Marie; Toffoli, Daniele; Christiansen, Ove

2009-07-30

85

Vibrationally Averaged Long-Range Molecule-Molecule Dispersion Coefficients from Coupled-Cluster Calculations  

NASA Astrophysics Data System (ADS)

Recent years have seen increasing interest in the structure and dynamics of molecular clusters formed when a chromophore molecule such as CO_2, OCS or N_2O is solvated by number of He atoms and/or para-H_2 molecules. A key experimental probe of their behaviour is the shift of a chromophore's vibrational transition frequency which occurs when the solvent species are attached to it. Such shifts are driven by the changes in the solvent-chromophore interaction potential upon vibrational excitation of the probe molecule. While `conventional' supermolecule calculations can often provide realistic predictions of such changes in the potential well and repulsive wall region, they become increasingly unreliable for describing the weak interactions at long range where most of the solvent species in a large cluster are located. It is therefore important to have accurate relative-orientation and monomer-stretching dependent long-range C_6, C_8 and C10 dispersion coefficients to incorporate into the models for the interaction potential and for its dependence on the chromophore's vibrational state. This paper describes how those coefficients can be obtained from calculated monomer dipole, quadrupole, and octupole polarizabilities for imaginary frequencies, and by making use of the Casimir-Polder relation and angular momentum coupling to extract orientation-dependent quantities. The calculations are performed using a modified version of the ACES2 program system which allows the calculation of dipole, quadrupole and octupole polarizabilities at the EOM-CCSD level, and of static multipole moments using CCSD(T) calculations and adequate basis sets. For each relevant level of the chromophore, vibrational averaging is performed by calculating the imaginary frequency polarizabilities at judiciously chosen geometries and performing a numerical integration using the free-molecule vibrational wavefunction. Subsequent work will involve merging this long-range part of the potential with a short-range part obtained from 'conventional' CCSD(T) calculations and using it in PIMC simulations of cluster behaviour. H. Li, N. Blinov, P.-N. Roy and R.J. Le Roy, J. Chem. Phys. 130, 144305 (2009).

Schmidt, Matthew; Nooijen, Marcel

2011-06-01

86

Vibrational spectroscopic studies and computational calculations of 5-chloro-2-(3-chlorophenylcarbamoyl)phenylacetate.  

PubMed

The FT-IR and FT-Raman spectra of 5-chloro-2-(3-chlorophenylcarbamoyl)phenylacetate were studied. The vibrational wave numbers and corresponding vibrational assignments were examined theoretically using the Gaussian 03 set of quantum chemistry codes and the normal modes are assigned by Potential Energy Distribution calculations. The synthesis, elemental analysis and NMR values are presented. The red shift of the NH stretching wave number in the infrared spectrum from the computed wave number indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom. The first hyperpolarizability, infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of nonlinear optics. The geometrical parameters of the title compound are in agreement with that of similar reported derivatives. PMID:22297035

Madhavan, V S; Mary, Y Sheena; Varghese, Hema Tresa; Panicker, C Yohannan; Mathew, Samuel; Van Alsenoy, Christian; Vinsova, Jarmila

2012-04-01

87

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

NASA Astrophysics Data System (ADS)

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

Park, G. Barratt

2014-10-01

88

Vibrational spectroscopy of \\  

Microsoft Academic Search

The vibrational spectroscopy of SO4 2? ·H2On is studied by theoretical calculations for n =1-5, and the results are compared with experiments for n =3-5. Thecalculations 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

Yifat Miller; Galina M. Chaban; Jia Zhou; Knut R. Asmis; Daniel M. Neumark

89

Dispersion corrected DFT approaches for anharmonic vibrational frequency calculations: nucleobases and their dimers.  

PubMed

Computational spectroscopy techniques have become in the last few years an effective means to analyze and assign infrared (IR) spectra of molecular systems of increasing dimensions and in different environments. However, transition from compilation of harmonic data to fully anharmonic simulations of spectra is still underway. The most promising results for large systems have been obtained, in our opinion, by perturbative vibrational approaches based on potential energy surfaces computed by hybrid (especially B3LYP) density functionals and medium size (e.g. SNSD) basis sets. In this framework, we are actively developing a comprehensive and robust computational protocol aimed at quantitative reproduction of the spectra of nucleic acid base complexes and their adsorption on solid supports (organic/inorganic). In this contribution we report the essential results of the first step devoted to isolated monomers and dimers. It is well known that in order to model the vibrational spectra of weakly bound molecular complexes dispersion interactions should be taken into proper account. In this work we have chosen two popular and inexpensive approaches to model dispersion interactions, namely the semi-empirical dispersion correction (D3) and pseudopotential based (DCP) methodologies both in conjunction with the B3LYP functional. These have been used for simulating fully anharmonic IR spectra of nucleobases and their dimers through generalized second order vibrational perturbation theory (GVPT2). We have studied, in particular, isolated adenine, hypoxanthine, uracil, thymine and cytosine, the hydrogen-bonded and stacked adenine and uracil dimers, and the stacked adenine-naphthalene heterodimer. Anharmonic frequencies are compared with standard B3LYP results and experimental findings, while the computed interaction energies and structures of complexes are compared to the best available theoretical estimates. PMID:24531740

Fornaro, Teresa; Biczysko, Malgorzata; Monti, Susanna; Barone, Vincenzo

2014-06-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

91

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

92

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

PubMed

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. PMID:23274252

Arivazhagan, M; Jeyavijayan, S; Geethapriya, J

2013-03-01

93

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

PubMed

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

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

2014-11-11

94

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

95

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

NASA Technical Reports Server (NTRS)

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

Chaban, Galina M.; Gerber, R. Benny

2002-01-01

96

Pentafluoroethyliminosulfur difluoride, CF 3CF 2N dbnd SF 2: Vibrational spectra and quantum chemical calculations  

NASA Astrophysics Data System (ADS)

The vibrational spectra of pentafluoroethyliminosulfur difluoride, CF 3CF 2N dbnd SF 2, were recorded in the gas phase with IR spectroscopy and in the liquid state with Raman spectroscopy. Quantum chemical calculations at the B3LYP (6-311+G(d) and 6-311+G(2df) basis sets) and MP2 levels of theory (6-31+G(d) and 6-311G(d) basis sets) were performed. According to all calculations the lowest energy conformer possesses C1 symmetry with syn orientation of the SF 2 group relative to the C sbnd N bond and near- trans orientation of the CF 3 group relative to the N dbnd S bond ( syn- trans). Calculations predict the hypothetical presence of a second stable conformer with anti-orientation of the SF 2 group ( anti- trans) which, however, possesses considerably higher energy and is therefore not observed in the analysis of the experimental spectra. The vibrational spectra were assigned for a single conformer in agreement with these calculations.

Robles, Norma L.; Cutin, Edgardo H.; Mews, Rüdiger; Della Védova, Carlos O.

2010-08-01

97

Ab Initio and Improved Empirical Potentials for the Calculation of the Anharmonic Vibrational States and Intramolecular Mode Coupling of N-Methylacetamide  

NASA Technical Reports Server (NTRS)

The second-order Moller-Plesset ab initio electronic structure method is used to compute points for the anharmonic mode-coupled potential energy surface of N-methylacetamide (NMA) in the trans(sub ct) configuration, including all degrees of freedom. The vibrational states and the spectroscopy are directly computed from this potential surface using the Correlation Corrected Vibrational Self-Consistent Field (CC-VSCF) method. The results are compared with CC-VSCF calculations using both the standard and improved empirical Amber-like force fields and available low temperature experimental matrix data. Analysis of our calculated spectroscopic results show that: (1) The excellent agreement between the ab initio CC-VSCF calculated frequencies and the experimental data suggest that the computed anharmonic potentials for N-methylacetamide are of a very high quality; (2) For most transitions, the vibrational frequencies obtained from the ab initio CC-VSCF method are superior to those obtained using the empirical CC-VSCF methods, when compared with experimental data. However, the improved empirical force field yields better agreement with the experimental frequencies as compared with a standard AMBER-type force field; (3) The empirical force field in particular overestimates anharmonic couplings for the amide-2 mode, the methyl asymmetric bending modes, the out-of-plane methyl bending modes, and the methyl distortions; (4) Disagreement between the ab initio and empirical anharmonic couplings is greater than the disagreement between the frequencies, and thus the anharmonic part of the empirical potential seems to be less accurate than the harmonic contribution;and (5) Both the empirical and ab initio CC-VSCF calculations predict a negligible anharmonic coupling between the amide-1 and other internal modes. The implication of this is that the intramolecular energy flow between the amide-1 and the other internal modes may be smaller than anticipated. These results may have important implications for the anharmonic force fields of peptides, for which N-methylacetamide is a model.

Gregurick, Susan K.; Chaban, Galina M.; Gerber, R. Benny; Kwak, Dochou (Technical Monitor)

2001-01-01

98

Structure and vibrational spectrum of 2-methylallyl radical. Nonempirical quantum chemical calculation  

SciTech Connect

In the study of the role of allyl type radicals in the pyrolysis of hydrocarbons it is of interest to investigate the conditions of formation, structure, and reactivity of 2-methylallyl radical (C/sub 4/H/sub 7//sup ./). The authors performed theoretical assignment of the bands, which were observed in the lattice spectra of the pyrolysis products, to the vibrations of the C/sub 4/H/sub 7//sup ./ radical by means of calculation of the frequencies and shapes of the normal vibrations. Since the necessary geometrical parameters and force coefficients of C/sub 4/H/sub 7//sup ./ are not known, they determined them by means of nonempirical quantum chemical calculation. The quantum chemical calculation of C/sub 4/H/sub 7//sup ./ was performed by means of the unrestricted Hartree-Fock method using STO-4G (geometry optimization taking into account the characteristics of calculation of radicals in minimal bases and calculation of the force coefficients by means of numerical differentiation) and 4-31G bases (electron density distribution) by means of GAUSSIAN-70 program. For comparison of the energy and electron density distribution they performed calculations also for the 2-methylallyl cation C/sub 4/H/sub 7//sup ./. From the calculation of the difference of the total energies of C/sub 4/H/sub 7//sup ./ and C/sub 4/H/sub 7//sup ./ in the 4-31G basis was 7.4 eV, which is comparable to the ionization energy of the 2-methylallyl radical, 7.95 eV.

Avakyan, V.G.; Volkova, V.V.; Gusel'nikov, L.E.; Ziegler, U.; Zimmermann, G.; Ondurshka, B.; Nametkin, N.S.

1987-04-01

99

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

Microsoft Academic Search

We apply the adiabatic switching (AS) method to determine the polyatomic classical motions that correspond to selected vibrational quantum states on multidimensional, anharmonic potential energy surfaces, and use these semiclassically quantized motions as initial conditions for quasiclassical trajectory (QCT) calculations of state-to-state reaction dynamics. Specifically, we calculate the classical motion corresponding to the quantum mechanical zero-point vibration of deuterated methane,

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

1995-01-01

100

Vibrational spectroscopic and quantum chemical calculations of (E)-N-Carbamimidoyl-4-((naphthalen-1-yl-methylene)amino)benzene sulfonamide.  

PubMed

FT-IR and FT-Raman spectra of (E)-N-Carbamimidoyl-4-((naphthalen-1-yl-methylene)amino)benzene sulfonamide were recorded and analyzed. The vibrational wavenumbers were computing at various levels of theory. The data obtained from theoretical calculations are used to assign vibrational bands obtained experimentally. The results indicate that B3LYP method is able to provide satisfactory results for predicting vibrational frequencies and structural parameters. The calculated first hyperpolarizability is comparable with reported values of similar derivatives and is an attractive object for future studies of non-linear optics. The geometrical parameters of the title compound are in agreement with that of similar derivatives. PMID:22153592

Chandran, Asha; Varghese, Hema Tresa; Mary, Y Sheena; Panicker, C Yohannan; Manojkumar, T K; Van Alsenoy, Christian; Rajendran, G

2012-02-15

101

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

NASA Astrophysics Data System (ADS)

The infrared spectra of gaseous and solid N-bromo-hexafluoro-2-propanimine, (CF3)2Cdbnd NBr, 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 Cs 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.

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

2012-05-01

102

Non-Born-Oppenheimer calculations of the pure vibrational spectrum of T2 including relativistic corrections  

NASA Astrophysics Data System (ADS)

We report very accurate calculations of the complete pure vibrational spectrum of the T2 molecule with an approach where the Born-Oppenheimer (BO) approximation is not assumed. As the considered states correspond to the zero total angular momentum, their non-BO wave functions are spherically symmetric and are expanded in terms of all-particle, one-center, spherically symmetric explicitly correlated Gaussian functions multiplied by even nonnegative powers of the internuclear distance. The nonrelativistic energies of the states obtained in the non-BO calculations are corrected for the relativistic effects of the order of ?2 (where ? is the fine structure constant) calculated as expectation values of the operators representing these effects.

Stanke, Monika; Adamowicz, Ludwik

2014-10-01

103

Non-Born-Oppenheimer calculations of the pure vibrational spectrum of T2 including relativistic corrections.  

PubMed

We report very accurate calculations of the complete pure vibrational spectrum of the T2 molecule with an approach where the Born-Oppenheimer (BO) approximation is not assumed. As the considered states correspond to the zero total angular momentum, their non-BO wave functions are spherically symmetric and are expanded in terms of all-particle, one-center, spherically symmetric explicitly correlated Gaussian functions multiplied by even nonnegative powers of the internuclear distance. The nonrelativistic energies of the states obtained in the non-BO calculations are corrected for the relativistic effects of the order of ?(2) (where ? is the fine structure constant) calculated as expectation values of the operators representing these effects. PMID:25338891

Stanke, Monika; Adamowicz, Ludwik

2014-10-21

104

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

NASA Astrophysics Data System (ADS)

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

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

1986-04-01

105

Ab initio calculation of vibrational dipole moment matrix elements. II. the water molecule as a polyatomic test case  

Microsoft Academic Search

This paper is the second part of a series devoted to the ab initio calculation of vibrational properties, like transition energies, dipole moment matrix elements and infrared intensities. The method of calculation has been detailed in the first paper, where test calculations on diatomic systems were also analyzed. The present paper applies the method to a simple polyatomic system, the

F. Culot; J. Liévin

1992-01-01

106

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

E-print Network

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

Price, Rachel Elizabeth

2011-01-01

107

Accurate variational calculations and analysis of the HOCl vibrational energy spectrum  

SciTech Connect

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

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

1998-12-01

108

Vibrational spectroscopic (FTIR and FT-Raman), first-order hyperpolarizablity, HOMO, LUMO, NBO, Mulliken charge analyses of 2-ethylimidazole based on Hartree-Fock and DFT calculations.  

PubMed

The FTIR and FT-Raman spectra of 2-ethylimidazole (2EIDZ) have been recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. 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 optimized molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p) basis set. 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 2EIDZ is also reported based on total energy distribution (TED). The values of the total dipole moment (?) and the first-order hyperpolarizability (?) of the compound were computed. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. Besides, HOMO and LUMO analysis, Mulliken's charge analysis and several thermodynamic properties have been calculated. PMID:25048284

Arivazhagan, M; Manivel, S; Jeyavijayan, S; Meenakshi, R

2015-01-01

109

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

110

A complete vibrational study on a potential environmental toxicant agent, the 3,3',4,4'-tetrachloroazobenzene combining the FTIR, FTRaman, UV-Visible and NMR spectroscopies with DFT calculations.  

PubMed

In this study 3,3',4,4'-tetrachloroazobenzene (TCAB) was prepared and then characterized by infrared, Raman, multidimensional nuclear magnetic resonance (NMR) and ultraviolet-visible spectroscopies. The density functional theory (DFT) together with the 6-31G(*) and 6-311++G(**) basis sets were used to study the structures and vibrational properties of the two cis and trans isomers of TCAB. The harmonic vibrational wavenumbers for the optimized geometries were calculated at the same theory levels. A complete assignment of all the observed bands in the vibrational spectra of TCAB was performed combining the DFT calculations with the scaled quantum mechanical force field (SQMFF) methodology. The molecular electrostatic potentials, atomic charges, bond orders and frontier orbitals for the two isomers of TCAB were compared and analyzed. The comparison of the theoretical ultraviolet-visible spectrum with the corresponding experimental demonstrates a good concordance while the calculated (1)H and (13)C chemicals shifts are in good conformity with the corresponding experimental NMR spectra of TCAB in solution. The npp(*) transitions for both forms were studied by natural bond orbital (NBO) while the topological properties were calculated by employing Bader's Atoms in the Molecules (AIM) theory. This study shows that the cis and trans isomers exhibit different structural and vibrational properties and absorption bands. PMID:25106816

Castillo, María V; Pergomet, Jorgelina L; Carnavale, Gustavo A; Davies, Lilian; Zinczuk, Juan; Brandán, Silvia A

2015-01-01

111

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

SciTech Connect

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.

Damian, J. I. Marquez; Granada, J. R. [Neutron Physics Department and Instituto Balseiro, Centro Atomico Bariloche, CNEA (Argentina); Malaspina, D. C. [Department of Biomedical Engineering and Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 (United States)

2013-07-14

112

SERS-measured and DFT-calculated vibrational spectra of p-Aminoazobenzene  

NASA Astrophysics Data System (ADS)

P-Aminoazobenzene (PAAB) is one of the 24kinds of carcinogenic azo dyes that the European Union forbids but it does not yet have an official method to detect PAAB. This paper experimentally observes the Normal Raman Spectrum(NRS) and infrared absorption spectrum of PAAB and presents theoretical vibrational spectra calculated from a density functional theory(DFT) method on the basis of B3LYP with 6 31 basis set. The calculated results show very good agreement with the experimentally observed IR and Raman frequencies. We also report the SERS spectra of PAAB adsorbed on silver and copper layers, which offer a sensitive but simple method to detect PAAB. Finally, the possible adsorbed states of PAAB on the silver and copper layers are discussed.

He, Tingchao; Li, Pengwei; Cai, Zhipeng; Mo, Yujun

2007-04-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

114

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

PubMed

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

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

2014-09-14

115

Calculation of the intensities of vibrational hydrogen sulfide transitions for remote sensing of high-temperature media  

NASA Astrophysics Data System (ADS)

Integral intensities of vibrational bands are calculated for hydrogen sulfide (H2S) taking into account the Fermi and Darling-Dennison resonances. Components of the dipole moment function in normal coordinates and parameters of the effective vibrational Hamiltonian borrowed from the literature are used as initial data. From several sets of the dipole moment function parameters, we have chosen the set of the parameters computations with which provide the closest agreement with the experimental integral intensities of the H2S bands. As a result, predictive computations of the vibrational band intensities (??? i = 2) are carried out at temperatures in the range 600-1500 K.

Voitsekhovskaya, O. K.; Egorov, O. V.

2012-09-01

116

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

NASA Astrophysics Data System (ADS)

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(N6) 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.

Bozkaya, U?ur; Sherrill, C. David

2013-08-01

117

The vibrational energies of ozone up to the dissociation threshold: Dynamics calculations on an accurate potential energy surface  

E-print Network

The vibrational energies of ozone up to the dissociation threshold: Dynamics calculations present an ab initio potential energy surface for the ground electronic state of ozone. It is global, i. All bound states of nonrotating ozone up to more than 99% of the dissociation energy are calculated

Farantos, Stavros C.

118

Calculations of N 2 triplet states vibrational populations and band emissions in venusian dayglow  

NASA Astrophysics Data System (ADS)

A model for N 2 triplet states band emissions in the venusian dayglow has been developed for low and high solar activity conditions. Steady state photoelectron fluxes and volume excitation rates for N 2 triplet states have been calculated using the Analytical Yield Spectra (AYS) technique. Model calculated photoelectron flux is in good agreement with Pioneer Venus Orbiter-observed electron flux. Since inter-state cascading is important for the triplet states of N 2, populations of different levels of N 2 triplet states are calculated under statistical equilibrium considering direct electron impact excitation, and cascading and quenching effects. Densities of all vibrational levels of each triplet state are calculated in the model. Height-integrated overhead intensities of N 2 triplet band emissions are calculated, the values for Vegard-Kaplan (A3?u+-X1?g+), First Positive (B3?g-A3?u+), Second Positive ( C3? u - B3? g), and Wu-Benesch ( W3? u - B3? g) bands of N 2, are 1.9 (3.2), 3 (6), 0.4 (0.8), and 0.5 (1.1) kR, respectively, for solar minimum (maximum) conditions. The intensities of the three strong Vegard-Kaplan bands (0, 5), (0, 6), and (0, 7) are 94 (160), 120 (204), and 114 (194) R, respectively, for solar minimum (maximum) conditions. Limb profiles are calculated for VK (0, 4), (0, 5), (0, 6) and (0, 7) bands. The calculated intensities on Venus are about a factor 10 higher than those on Mars. The present study provides a motivation for a search of N 2 triplet band emissions in the dayglow of Venus.

Bhardwaj, Anil; Jain, Sonal Kumar

2012-02-01

119

Vinylphosphine-borane: synthesis, gas phase infrared spectroscopy, and quantum chemical vibrational calculations.  

PubMed

Both experimental and theoretical investigations are reported on the infrared spectrum of vinylphosphine-borane (CH(2)=CHPH(2) x BH(3)), a donor-acceptor complex. The gas phase infrared spectra (3500-600 cm(-1)) have been recorded at 0.5 cm(-1) resolution. This first primary alpha,beta-unsaturated phosphine-borane synthesized up to now is kinetically very unstable in the gas phase and decomposes rapidly into two fragments: the free vinylphosphine CH(2)=CHPH(2) and the monoborane BH(3) which dimerizes to form the more stable diborane B(2)H(6). Spectra of free CH(2)=CHPH(2) and B(2)H(6) compounds were also recorded to assign some vibration modes of the complex in very dense spectral regions. The analysis was completed by carrying out quantum mechanical calculations by density functional theory method at the B3LYP/6-31+G(**) level. Anharmonic frequencies and infrared intensities of the two predicted gauche and syn conformers of the vinylphosphine-borane complex were calculated in the 3500-100 cm(-1) region with the use of a variational approach, implemented in the P_ANHAR_V1.2 code. Because of the relatively weak interaction between the vinylphosphine and the monoborane, the vibrations of the complex can easily be subdivided into modes localized in the CH(2)=CHPH(2) and BH(3) moieties and into "intermolecular" modes. Localized modes are unambiguously correlated with the modes of the isolated monomers. Therefore, they are described in terms of the monomer vibrations, and the complexation shifts are defined as Delta nu = nu(complex) - nu(monomer) to make the effect of the complexation precise on each localized mode. In this objective, anharmonic frequencies and infrared intensities of the BH(3) monomer and the stable gauche and syn conformers of the free vinylphosphine were obtained at the same level of theory. In the gas phase, only the syn form of the complex was observed and assigned. All theoretically predicted frequencies and complexation shifts in magnitude and direction are in good agreement with experiment. By infrared spectroscopy assisted by quantum chemical calculations, the consequences of the complexation of an alpha,beta-unsaturated phosphine by borane on the physicochemical properties of the formed 12-atom complex have been efficiently evaluated. PMID:19071917

Khater, Brahim; Guillemin, Jean-Claude; Benidar, Abdessamad; Bégué, Didier; Pouchan, Claude

2008-12-14

120

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

121

Full-dimensional quantum calculations of the vibrational states of H5(+).  

PubMed

Full-dimensional quantum calculations of the vibrational states of H5(+) have been performed on the accurate potential energy surface developed by Xie et al. [J. Chem. Phys. 122, 224307 (2005)]. The zero point energies of H5(+), H4D(+), D4H(+), and D5(+) and their ground-state geometries are presented and compared with earlier theoretical results. The first 10 low-lying excited states of H5(+) are assigned to the fundamental, overtone, and combination of the H2-H3(+) stretch, the shared proton hopping and the out-of-plane torsion. The ground-state torsional tunneling splitting, the fundamental of the photon hopping mode and the first overtone of the torsion mode are 87.3 cm(-1), 354.4 cm(-1), and 444.0 cm(-1), respectively. All of these values agree well with the diffusion Monte Carlo and multi-configuration time-dependent Hartree results where available. PMID:23556725

Song, Hongwei; Lee, Soo-Ying; Yang, Minghui; Lu, Yunpeng

2013-03-28

122

DFT Ab initio Calculation of Vibrational Frequencies in AsSe glass  

NASA Astrophysics Data System (ADS)

By using DFT double zeta wave functions, we calculated the structure, bond length (picometer, pm), frequencies(intensities)[degeneracy] for various clusters of arsenic selenide. Our results are as follows. (i) AsSe(diatomic) bond length 216pm, 244.0(1/cm). (ii) As2Se(linear) bond length 228.5 pm, frequencies 27.6(1.9) and 387.6(4.3). (iii) As2Se(triangular) As-Se 243.4 pm, As-As 223.3 pm, frequencies 237.3(2.4) and 332.4(0.05)(1/cm). (iv) As3Se (triangular) bond length 238.4 pm, frequencies 107.5 and 296(weak)(1/cm). (v) As4Se (square) bond length 250.2 pm, 58.5(0.04), 241.3(5.9)(1/cm). (vi) AsSe3 (triangular), bond length 231.2 pm, 75.9(0.003), 103.5(1.26)[2], 350.9(33.2)[2]. From this study we identify that linear As-Se-As for which the calculated frequency is 27.6(1/cm) is in agreement with the data of Nemanich, Phys. Rev. B 16, 1655(1977), J. C. Phillips et al Phys. Rev B 21, 5724(1980). We have successfully calculated several vibrational frequencies accurately which agree with the Raman data. *V. R. Devi et al J. Non-Cryst. Solids 351, 489(2005);353,111(2007)

Shrivastava, Keshav; Kassim, Hasan; Nazrul Rosli, Ahmad

2008-03-01

123

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

PubMed

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 454K) 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 11-480K are analyzed. PMID:23851177

Drozd, M; Dudzic, D

2013-11-01

124

Calculation of the Vibrational Stark Effect Using a First-Principles QM/MM Approach  

PubMed Central

The proper description of the electric environment of condensed phases is a critical challenge for force field methods. To test and validate the ability of the CHARMM additive force field to describe the electric environment in aqueous solution combined QM/MM calculations have been used to calculate the vibrational Stark effect (VSE). We utilized a first principles methodology using correlated electronic structure techniques to compute the Stark shift between the gas phase and solvent environments and between two different solvent environments of three VSE probes containing acetonitrile or fluorine functionalities which have been well-characterized experimentally. Reasonable agreement with the experimentally determined Stark shifts is obtained when the MM atoms are described by the CHARMM additive force field, though it is essential to employ an anharmonic correction in the frequency calculation. In addition, the electric field created by the solvent is computed along the CN bond and a theoretical Stark tuning rate is determined for acetonitrile and shown to be in satisfactory agreement with experiment. PMID:21423871

Ringer, Ashley L.; MacKerell, Alexander D.

2011-01-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

126

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

NASA Astrophysics Data System (ADS)

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

Leadenham, S.; Erturk, A.

2014-11-01

127

First-principles calculations on the electronic, vibrational, and optical properties of semiconductor nanowires  

NASA Astrophysics Data System (ADS)

The semiconductor nanowire (NW) has attracted significant attention as a new one-dimensional structure for fundamental studies and also as a potential building block for nanodevices. When the size of NWs becomes close to the order of the de Broglie wavelength of electrons, the quantum confinement effect significantly affects the electronic behaviors of NWs and raises expectations for many novel applications in microelectronics. As the technology advances, more and more fine semiconductor NWs are fabricated in the laboratories, which provide good platforms to study the special properties of low-dimensional systems. From these new nanostructures, we choose to study the single crystal silicon nanowire (SiNW). One advantage of this choice of SiNWs is that we have the solid and complete knowledge about the electronic structure of bulk silicon, which provides valuable information for us to understand the quantum confinement effect in SiNWs. The other reason for this choice is that the silicon-based technology is so highly developed that scientists prefer silicon as the elementary material for the cost consideration, even it may not be the highest performance candidate. Therefore, our calculations on SiNWs should be useful for the industrial development of today's nanotechnology. As a starting point, we begin by studying the ground electronic state of SiNWs and performing calculations on the following three physical properties. Based on thorough knowledge about the ground state of electrons, the first part of our work is to calculate the properties of lattice vibrations of SiNWs. The density functional theory (DFT) based linear-response method is used to obtain lattice vibrational modes. We plot the density of vibrational modes at the Gamma point of the Brillouin zone and show a clear evolutionary from bulk silicon to the narrow SiNW. Two kinds of frequency shifts of lattice vibrational modes are found: One is the red shift of the optical modes, the other is the blue shift of the radial breathing modes (RBMs). We discover that the size dependence of the frequency shifts of RBMs can be described well by the elastic model with the cylindrical boundary confinement. In order to characterize these confined modes in SiNWs, we calculate the first-order Raman activities of the smallest SiNW, and find that the RBM is strongly active in the scattering spectrum. Therefore, our calculated result about the size dependence of the frequency of RBM provides an easy way to estimate the size of the nanowires from the corresponding Raman spectrum. The excited-state properties of nanostructures are of critical importance in the design of functional optical devices. The low dimensionality and reduced size tend to strengthen the effective Coulomb interaction in nanostructures. Quantitative evaluations of physical properties manifesting this effect are therefore timely and valuable to the nanotechnology research. In the second part of my work, we focus on the correlated electron-hole states in semiconductor NWs and their influence on the optical absorption spectrum. First-principles calculations are performed for an isolated hydrogen-passivated SiNW with a diameter of 1.2 nm. By using plane waves and pseudopotentials, the quasiparticle states are calculated within the many-body perturbation theory with the so-called GW approximation, and the electron-hole interaction is evaluated with the Bethe-Salpeter equation (BSE). The enhanced Coulomb interaction in this confined system results in an unusually large shift (1-2 eV) of the optical spectrum as well as a significant increase in certain absorption peak intensity. The current results predict anomalous excited-state properties in semiconductor NWs that may impact future applications of these nanostructures. In the third part of my work, the electronic band structures of Si/Ge core-shell NWs are studied with first-principles calculations. The electronic states close to the band gap of NWs along the [110] direction are found to be confined within the core and the shell, respectively. Our calculated resul

Yang, Li

128

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. Program summaryProgram title: DAMPING Catalogue identifier: AEIS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIS_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.: 84 108 No. of bytes in distributed program, including test data, etc.: 2 581 423 Distribution format: tar.gz Programming language: FORTRAN Computer: Any computer or work station Operating system: Any with a Fortran compiler RAM: 8 Mbytes, using double precision arithmetic, with 400×200 grid points, on an ALPHA server Classification: 19.8 External routines: Requires a link to the NAG libraries for the Bessel functions subroutines. Nature of problem: The computer program calculates generalized expressions for the anti-Hermitian part of the relativistic dielectric tensor in a plasma for an arbitrary distribution function, with comparison to the analytical expressions derived in [1], associated with a relativistic Maxwellian distribution, for any n-th cyclotron harmonic and for the relativistic Landau damping case when n=0. The anti-Hermitian parts of the dielectric tensor are important to know, since they determine the damping or emission of an electromagnetic wave within the plasma medium. New analytical expressions are derived for the relativistic Landau damping and for the electron cyclotron damping including the case n=1, for the case of an arbitrary distribution function. This is important since studies of the RF heating of tokamak plasmas in a fully self-consistent way involve the simultaneous description of the temporal evolution of the heated species velocity distribution function using a Fokker-Planck code, coupled to the damping of the wave on the evolving distribution function. We can evaluate numerically the degree by which a non-Maxwellian nature of the relativistic distribution function changes the Landau damping and the electron cyclotron damping, with respect to the Maxwellian case. In addition this is also important in the study of electron cyclotron emission, which can be a sensitive indicator of non-thermal electron distributions. Solution method: The relativistic expressions for the anti-Hermitian parts of the dielectric tensor elements can be expressed as a single integral over the parallel momentum variable [1]. This single integral is calculated along the resonance curve, for an arbitrary distribution function calculated from a relativistic Fokker-Planck code. Since Fokker-Planck codes usually evolve the distribution functions using a spherical coordinate system in momentum space, the present code has to first transform the distribution function calculated by the Fokker-Planck code from a spherical coordinate system to a cylindrical coordinate system in momentum space, where the single integral over the parallel momentum variable can be calculated along the resonance c

Shkarofsky, I.; Shoucri, M.

2011-07-01

129

Calculation of specific, highly excited vibrational states based on a Davidson scheme: application to HFCO.  

PubMed

We present the efficiency of a new modified Davidson scheme which yields selectively one high-energy vibrationally excited eigenstate or a series of eigenstates. The calculation of a highly vibrationally excited state psi located in a dense part of the spectrum requires a specific prediagonalization step before the Davidson scheme. It consists in building a small active space P containing the zero-order states which are coupled with the zero-order description of the eigenstate of interest. We propose a general way to define this active space P which plays a crucial role in the method. The efficiency of the method is illustrated by computing and analyzing the high-energy excited overtones of the out-of-plane mode [formula: see text] in HFCO. These overtone energies correspond to the 234th, 713th, and 1774th energy levels in our reference basis set which contains roughly 140,000 states. One of the main advantages of this Davidson scheme comes from the fact that the eigenstate and eigenvalue convergence can be assessed during the iterations by looking at the residual [formula: see text]. The maximum value epsilon allowed for this residual constitutes a very sensitive and efficient parameter which sets the accuracy of the eigenvalues and eigenstates, even when the studied states are highly excited and are localized in a dense part of the spectrum. The physical analysis of the eigenstates associated with the 5th, 7th, and 9th out-of-plane overtones in HFCO provides some interesting information on the energy localization in this mode and on the role played by the in-plane modes. Also, it provides some ideas on the numerical methods which should be developed in the future to tackle higher-energy excited states in polyatomics. PMID:16375515

Iung, Christophe; Ribeiro, Fabienne

2005-11-01

130

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

2013-09-01

131

Calculation of the Vibrational Properties of Chlorophyll a in Solution Sreeja Parameswaran, Ruili Wang, and Gary Hastings*  

E-print Network

Calculation of the Vibrational Properties of Chlorophyll a in Solution Sreeja Parameswaran, Ruili, Georgia 30303 ReceiVed: July 10, 2008; ReVised Manuscript ReceiVed: August 26, 2008 Chlorophyll a (Chl species at the heart of all solar capture and conversion processes is chlorophyll a (Chl-a), either

Hastings, Gary

132

Analysis on problem of removing the odd point in rotors torsional vibration characteristics' calculation using Riccati method  

Microsoft Academic Search

Aiming at the problem of the odd point in the calculation of rotors torsional vibration characteristics by using the improved Riccati method, this paper presents a new viewpoint about how to confirm and remove the lost root and the accessional root.

Dan-Mei Xie; Juan Huang; Jian-Feng Wan; Ye Yuan

2003-01-01

133

Response calculations of electronic and vibrational transitions in molecular oxygen induced by interaction with noble gases.  

PubMed

The Einstein coefficient for the singlet oxygen emission a1Deltag-->X3Sigmag- at lambda=1270 nm and b1Sigmag+-->X3Sigmag- emission at lambda=750 nm were calculated by quadratic response (QR) multiconfiguration self-consisted field (MCSCF) method for a number of collision complexes O2+M, where M=He, Ne, Ar. Interaction with He clusters was studied in order to simulate cooperative effect of the environment on the oxygen emission. Calculations of the dipole transition moment for the Noxon band, b1Sigmag+-a1Deltag, by linear response (LR) MCSCF method were also performed for a number of collision complexes. Spin-orbit coupling (SOC) between the b1Sigmag+ and X3Sigmag- (MS=0) states does not change much upon collisions, thus the a-X transition borrows intensity mostly from the collision-induced Noxon band b-a. The a-X intensity borrowing from the Schumann-Runge transition is negligible. The calculations show that the b-a and a-X transition probabilities are enhanced approximately by 10(5) and 10(3) times by O2+M collisions. An order of magnitude differences occur for both transitions for noble gases with large difference in polarizability. A strong cooperative effect is obtained when few He atoms perturb the oxygen molecule. Depending on mutual orientation of the partners it can be a complete quenching of the a-->X emission or strong non-additive enhancement. Collision-induced infrared vibrational transitions in a number of molecular oxygen excited states were studied and shown to be state selective. PMID:14607236

Minaev, Boris F; Kobzev, G I

2003-12-01

134

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

135

Matching Rules for Collective Behaviors on Complex Networks: Optimal Configurations for Vibration Frequencies of Networked Harmonic Oscillators  

PubMed Central

The structure-dynamics-function has become one of central problems in modern sciences, and it is a great challenge to unveil the organization rules for different dynamical processes on networks. In this work, we study the vibration spectra of the classical mass spring model with different masses on complex networks, and pay our attention to how the mass spatial configuration influences the second-smallest vibrational frequency () and the largest one (). For random networks, we find that becomes maximal and becomes minimal if the node degrees are point-to-point-positively correlated with the masses. In these cases, we call it point-to-point matching. Moreover, becomes minimal under the condition that the heaviest mass is placed on the lowest-degree vertex, and is maximal as long as the lightest mass is placed on the highest-degree vertex, and in both cases all other masses can be arbitrarily settled. Correspondingly, we call it single-point matching. These findings indicate that the matchings between the node dynamics (parameter) and the node position rule the global systems dynamics, and sometimes only one node is enough to control the collective behaviors of the whole system. Therefore, the matching rules might be the common organization rules for collective behaviors on networks. PMID:24386088

Zhan, Meng; Liu, Shuai; He, Zhiwei

2013-01-01

136

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

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

137

FT-IR and Raman spectra vibrational assignments and density functional calculations of 1-naphthyl acetic acid.  

PubMed

This work deals with the vibrational spectroscopy of 1-naphthyl acetic acid. The molecular vibrations of 1-naphthyl acetic acid (NAA) is investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopy. In parallel, ab initio and various density functional (DFT) methods were used to determine the geometrical, energetic and vibrational characteristics of NAA. On the basis of B3LYP/6-311+G** method and basis set combinations, a normal mode analysis was performed to assign the various fundamental frequencies according to the total energy distribution (TED). Simulation of infrared and Raman spectra, utilizing the results of these calculations led to excellent overall agreement with observed spectral patterns by refinement of scale factors. PMID:17804282

Krishnakumar, V; Mathammal, R; Muthunatesan, S

2008-06-01

138

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

PubMed

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

Ma?olepsza, Edyta; Straub, John E

2014-07-17

139

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

PubMed

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

Halverson, Thomas; Poirier, Bill

2014-05-28

140

Anharmonic OH vibrations in Mg(OH)2 (brucite): two-dimensional calculations and crystal-induced blueshift.  

PubMed

A two-dimensional quantum-mechanical vibrational model has been used to calculate the anharmonic OH vibrational frequencies in the layered Mg(OH)(2) (brucite) crystal. The underlying potential energy surface was generated by density functional theory (DFT) calculations. The resulting OH frequencies are upshifted (blueshifted) by about +75 cm(-1) with respect to the gas-phase OH frequency (+120 cm(-1) in experiments; the discrepancy is mainly due to inadequacies in the DFT and pseudopotential models). The Raman-IR split is about 50 cm(-1), both in the calculations and in experiments. We find that the blueshift phenomenon in brucite can qualitatively be explained by a parabolalike "OH frequency versus electric field" correlation curve pertaining to an OH(-) ion exposed to an electric field. We also find that it is primarily the neighbors within the Mg(OH)(2) layer that induce the blueshift while the interlayer interaction gives a smaller (and redshifting) contribution. PMID:20059089

Hermansson, Kersti; Probst, Michael M; Gajewski, Grzegorz; Mitev, Pavlin D

2009-12-28

141

A calculation method for torsional vibration of a crankshafting system with a conventional rubber damper by considering rubber form  

SciTech Connect

The cheap and compact rubber dampers of shear-type have been widely employed as the torsional vibration control of the crankshaft system of high-speed, automobile diesel engines. The conventional rubber dampers have various rubber forms owing to the thorough investigation of optimum dampers in the design stage. Their rubber forms can be generally grouped into three classes such as the disk type, the bush type and the composite type. The disk type and the bush type rubber dampers are called the basic-pattern rubber dampers hereafter. The composite type rubber part is supposed to consist of the disk type and the bush type parts, regarded respectively as the basic patterns of the rubber part, at large. The dynamic characteristics of the vibration isolator rubber depend generally on temperature, frequency, strain amplitude, shape and size effect,s so it is difficult to estimate accurately their characteristics. With the present technical level, it is also difficult to determine the suitable rubber geometry which optimizes the vibration control effect. The study refers to the calculation method of the torsional vibration of a crankshaft system with a shear-type rubber damper having various rubber forms in order to offer the useful method for optimum design. In this method, the rheological formula of the three-element Maxwell model, from which the torsional stiffness and the damping coefficient of the damper rubber part in the equivalent vibration system are obtained, are adopted in order to decide the dynamic characteristics of the damper rubber part.

Kodama, Tomoaki; Honda, Yasuhiro; Wakabayashi, Katsuhiko; Iwamoto, Shoichi

1996-09-01

142

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

NASA Astrophysics Data System (ADS)

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

Homayoon, Zahra; Bowman, Joel M.

2014-10-01

143

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

144

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

PubMed

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

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

2014-03-31

145

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

146

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

NASA Astrophysics Data System (ADS)

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

Appalakondaiah, S.; Vaitheeswaran, G.; Lebègue, S.

2014-01-01

147

Study of conformational stability, structural, electronic and charge transfer properties of cladrin using vibrational spectroscopy and DFT calculations  

NASA Astrophysics Data System (ADS)

In the present work, a detailed conformational study of cladrin (3-(3,4-dimethoxy phenyl)-7-hydroxychromen-4-one) has been done by using spectroscopic techniques (FT-IR/FT-Raman/UV-Vis/NMR) and quantum chemical calculations. The optimized geometry, wavenumber and intensity of the vibrational bands of the cladrin in ground state were calculated by density functional theory (DFT) employing 6-311++G(d,p) basis sets. The study has been focused on the two most stable conformers that are selected after the full geometry optimization of the molecule. A detailed assignment of the FT-IR and FT-Raman spectra has been done for both the conformers along with potential energy distribution for each vibrational mode. The observed and scaled wavenumber of most of the bands has been found to be in good agreement. The UV-Vis spectrum has been recorded and compared with calculated spectrum. In addition, 1H and 13C nuclear magnetic resonance spectra have been also recorded and compared with the calculated data that shows the inter or intramolecular hydrogen bonding. The electronic properties such as HOMO-LUMO energies were calculated by using time-dependent density functional theory. Molecular electrostatic potential has been plotted to elucidate the reactive part of the molecule. Natural bond orbital analysis was performed to investigate the molecular stability. Non linear optical property of the molecule have been studied by calculating the electric dipole moment (?) and the first hyperpolarizability (?) that results in the nonlinearity of the molecule.

Singh, Swapnil; Singh, Harshita; Srivastava, Anubha; Tandon, Poonam; Sinha, Kirti; Bharti, Purnima; Kumar, Sudhir; Kumar, Padam; Maurya, Rakesh

2014-11-01

148

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

149

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

NASA Astrophysics Data System (ADS)

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

Zhang, Feng; Hayashi, Michitoshi; Wang, Houng-Wei; Tominaga, Keisuke; Kambara, Ohki; Nishizawa, Jun-ichi; Sasaki, Tetsuo

2014-05-01

150

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

PubMed

The phonon modes of molecular crystals in the terahertz frequency region often feature delicately coupled inter- and intra-molecular vibrations. Recent advances in density functional theory such as DFT-D(*) have enabled accurate frequency calculation. However, the nature of normal modes has not been quantitatively discussed against experimental criteria such as isotope shift (IS) and correlation field splitting (CFS). Here, we report an analytical mode-decoupling method that allows for the decomposition of a normal mode of interest into intermolecular translation, libration, and intramolecular vibrational motions. We show an application of this method using the crystalline anthracene system as an example. The relationship between the experimentally obtained IS and the IS obtained by PBE-D(*) simulation indicates that two distinctive regions exist. Region I is associated with a pure intermolecular translation, whereas region II features coupled intramolecular vibrations that are further coupled by a weak intermolecular translation. We find that the PBE-D(*) data show excellent agreement with the experimental data in terms of IS and CFS in region II; however, PBE-D(*) produces significant deviations in IS in region I where strong coupling between inter- and intra-molecular vibrations contributes to normal modes. The result of this analysis is expected to facilitate future improvement of DFT-D(*). PMID:24811648

Zhang, Feng; Hayashi, Michitoshi; Wang, Houng-Wei; Tominaga, Keisuke; Kambara, Ohki; Nishizawa, Jun-ichi; Sasaki, Tetsuo

2014-05-01

151

First-principles calculations of the electronic, vibrational, and elastic properties of the magnetic laminate Mn2GaC  

NASA Astrophysics Data System (ADS)

In this paper, we report the by first-principles predicted properties of the recently discovered magnetic MAX phase Mn2GaC. The electronic band structure and vibrational dispersion relation, as well as the electronic and vibrational density of states, have been calculated. The band structure close to the Fermi level indicates anisotropy with respect to electrical conductivity, while the distribution of the electronic and vibrational states for both Mn and Ga depend on the chosen relative orientation of the Mn spins across the Ga sheets in the Mn-Ga-Mn trilayers. In addition, the elastic properties have been calculated, and from the five elastic constants, the Voigt bulk modulus is determined to be 157 GPa, the Voigt shear modulus 93 GPa, and the Young's modulus 233 GPa. Furthermore, Mn2GaC is found relatively elastically isotropic, with a compression anisotropy factor of 0.97, and shear anisotropy factors of 0.9 and 1, respectively. The Poisson's ratio is 0.25. Evaluated elastic properties are compared to theoretical and experimental results for M2AC phases where M = Ti, V, Cr, Zr, Nb, Ta, and A = Al, S, Ge, In, Sn.

Thore, A.; Dahlqvist, M.; Alling, B.; Rosén, J.

2014-09-01

152

Refined calculation of the magnetic susceptibility and polarizability of the BH molecule in different vibrational levels of the ground electronic state  

SciTech Connect

Refined calculations of the dependence of the components of the magnetic susceptibility and polarizability of the BH molecule in the electronic ground state on the vibrational quantum number have been carried out. It has been found that, as the vibrational quantum number increases from v = 0 to v = 17, the transverse magnetic susceptibility averaged over the molecular vibrations increases by a factor of 7.1, while the longitudinal polarizability increases by a factor of 2.2. The results obtained confirm the sharp increase in the anomalous paramagnetic susceptibility of the BH molecule upon excitation of the vibrational levels of its ground electronic state predicted in the preceding work of the authors.

Braun, P.A.; Rebane, T.K.; Semakova, O.I.

1987-06-01

153

Semiempirical valence-electron calculations of excited state geometries and vibrational frequencies  

Microsoft Academic Search

Summary The use of finite differences and finite second differences in order to approximate gradients and second derivatives of the energy for geometry optimization and determination of normal modes of vibration on the CI level of computation is discussed in connection with the semiempirical MNDOC-CI valence electron method. Results are given for ground and excited states of ethylene, acetylene, formaldehyde,

M. Klessinger; T. Pötter; Ch. v. Wüllen

1991-01-01

154

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

E-print Network

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

de Vries, Mattanjah S.

155

Conformational and Vibrational Studies of Triclosan  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

156

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

NASA Astrophysics Data System (ADS)

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

Balachandran, V.; Janaki, A.; Nataraj, A.

2014-01-01

157

Tabulation of hybrid theory calculated e-N2 vibrational and rotational cross sections  

NASA Technical Reports Server (NTRS)

Vibrational excitation cross sections of N2 by electron impact are tabulated. Integrated cross sections are given for transitions v yields v prime where o=or v=or 8 in the energy range 0.1 eV=or E=or 10 eV. The energy grid is chosen to be most dense in the resonance region (2 to 4 eV) so that the substructure is present in the numerical results. Coefficients in the angular distribution formula (differential scattering cross section) for transitions v=0 yields v prime = or 8 are also numerically given over the same grid of energies. Simultaneous rotation-vibration coefficients are also given for transitions v=o,j=o; 1 yields v prime=o, j=o,2,4; 1,3,5. All results are obtained from the hybrid theory.

Chandra, N.; Temkin, A.

1976-01-01

158

Use of a nondirect-product basis for treating singularities in triatomic rotational-vibrational calculations.  

PubMed

A technique has been developed which in principle allows the determination of the full rotational-vibrational eigenspectrum of triatomic molecules by treating the important singularities present in the triatomic rotational-vibrational kinetic energy operator given in Jacobi coordinates and the R(1) embedding. The singular term related to the diatom-type coordinate, R(1), deemed to be unimportant for spectroscopic applications, is given no special attention. The work extends a previous [J. Chem. Phys., 2005, 122, 024101] vibration-only approach and employs a generalized finite basis representation (GFBR) resulting in a nonsymmetric Hamiltonian matrix [J. Chem. Phys., 2006, 124, 014110]. The basis set to be used is obtained by taking the direct product of a 1-D DVR basis, related to R(1), with a 5-D nondirect-product basis, the latter formed by coupling Bessel-DVR functions depending on the distance-type coordinate causing the singularity, associated Legendre polynomials depending on the Jacobi angle, and rotational functions depending on the three Euler angles. The robust implicitly restarted Arnoldi method within the ARPACK package is used for the determination of a number of eigenvalues of the nonsymmetric Hamiltonian matrix. The suitability of the proposed approach is shown by the determination of the rotational-vibrational energy levels of the ground electronic state of H(3)(+) somewhat above its barrier to linearity. Convergence of the eigenenergies is checked by an alternative approach, employing a Hamiltonian expressed in Radau coordinates, a standard direct-product basis, and no treatment of the singularities. PMID:17664964

Czakó, Gábor; Furtenbacher, Tibor; Barletta, Paolo; Császár, Attila G; Szalay, Viktor; Sutcliffe, Brian T

2007-07-14

159

Force field calculation for inplane vibrations of ethylene using cndo \\/Force method  

Microsoft Academic Search

cndo\\/Force method is used to evaluate redundancy-free internal valence force field (rfivff) for inplane vibrations of ethylene. The bending force constants, the stretch-band and bend-bend interaction force constants\\u000a are predicted reasonably well in magnitude and sign by this method; whereas stretching force constants and stretch-stretch\\u000a interactions are overestimated. Initial force field is set up by transferring stretching force constants from

A Jothi; G Shanmugam; A Annamalai; Surjit Singh

1982-01-01

160

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

161

Characterization of a genuin iron(V) - nitrido species by nuclear resonant vibrational spectroscopy coupled to density functional calculations.  

SciTech Connect

The characterization of high-valent iron species is of interest due to their relevance to biological reaction mechanisms. Recently, we have synthesized and characterized an [Fe(V)-nitrido-cyclam-acetato]{sup +} complex, which has been characterized by M{umlt o}ssbauer, magnetic susceptibility data, and XAS spectroscopies combined with DFT calculations . The results of this study indicated that the [Fe(V)-nitrido-cyclam-acetato]+ complex is an unusual d{sup 3} system with a nearly orbitally degenerate S = 1/2 ground state. Although the calculations predicted fairly different Fe-N stretching frequencies for the S = 1/2 and the competing S = 3/2 ground states, a direct experimental determination of this important fingerprint quantity was missing. Here we apply synchrotron-based nuclear resonance vibrational scattering (NRVS) to characterize the Fe-N stretching frequency of an Fe(V)-nitrido complex and its Fe(III)-azide precursor. The NRVS data show a new isolated band at 864 cm{sup -1} in the Fe(V)-nitrido complex that is absent in the precursor. The NRVS spectra are fit and simulated using a DFT approach, and the new feature is unambiguously assigned to a Fe(V)-N stretch. The calculated Fe-N stretching frequency is too high by {approx}75 cm{sup -1}. Anharmonic contributions to the Fe-N stretching frequency have been evaluated and have been found to be small (-5.5 cm{sup -1}). The NRVS data provided a unique opportunity to obtain this vibrational information, which had eluded characterization by more traditional vibrational spectroscopies.

Petrenko, T.; George, S. D.; Aliaga-Alcalde, N.; Bill, E.; Mienert, B.; Xiao, Y.; Guo, Y.; Sturhahn, W.; Cramer, S.P.; Wieghardt, K.; Neese, F.; X-Ray Science Division; Institut of Physikalische und Theoretische Chemie; SSRL; Standford Univ.; Max-Planck Institut fur Bioanogranische Chemie; Univ. of California at Davis; LBNL

2007-01-01

162

Characterization of a Genuine Lron(V)-Nitrido Species By Nuclear Resonant Vibrational Spectroscopy Coupled to Density Functional Calculations  

SciTech Connect

The characterization of high-valent iron species is of interest due to their relevance to biological reaction mechanisms. Recently, we have synthesized and characterized an [Fe(V)-nitrido-cyclam-acetato]+ complex, which has been characterized by M{umlt o}ssbauer, magnetic susceptibility data, and XAS spectroscopies combined with DFT calculations. The results of this study indicated that the [Fe(V)-nitrido-cyclam-acetato]+ complex is an unusual d3 system with a nearly orbitally degenerate S = 1/2 ground state. Although the calculations predicted fairly different Fe-N stretching frequencies for the S = 1/2 and the competing S = 3/2 ground states, a direct experimental determination of this important fingerprint quantity was missing. Here we apply synchrotron-based nuclear resonance vibrational scattering (NRVS) to characterize the Fe-N stretching frequency of an Fe(V)-nitrido complex and its Fe(III)-azide precursor. The NRVS data show a new isolated band at 864 cm-1 in the Fe(V)-nitrido complex that is absent in the precursor. The NRVS spectra are fit and simulated using a DFT approach, and the new feature is unambiguously assigned to a Fe(V)-N stretch. The calculated Fe-N stretching frequency is too high by {approx}75 cm-1. Anharmonic contributions to the Fe-N stretching frequency have been evaluated and have been found to be small (-5.5 cm-1). The NRVS data provided a unique opportunity to obtain this vibrational information, which had eluded characterization by more traditional vibrational spectroscopies.

Petrenko, T.; George, S.D.; Aliaga-Alcalde, N.; Bill, E.; Mienert, B.; Xiao, Y.; Guo, Y.; Sturhahn, W.; Cramer, S.P.; Wieghardt, K.; Neese, F.; /Bonn U., LTC /SLAC, SSRL /Max Planck Inst., Mulheim /UC, Davis /Argonne /LBL, Berkeley

2007-10-19

163

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

1998-08-01

164

Calculation of Vibrational Shifts of Nitrile Probes in the Active Site of Ketosteroid Isomerase upon Ligand Binding  

PubMed Central

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 analog 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 CNH 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.

2012-01-01

165

Study of conformational stability, structural, electronic and charge transfer properties of cladrin using vibrational spectroscopy and DFT calculations.  

PubMed

In the present work, a detailed conformational study of cladrin (3-(3,4-dimethoxy phenyl)-7-hydroxychromen-4-one) has been done by using spectroscopic techniques (FT-IR/FT-Raman/UV-Vis/NMR) and quantum chemical calculations. The optimized geometry, wavenumber and intensity of the vibrational bands of the cladrin in ground state were calculated by density functional theory (DFT) employing 6-311++G(d,p) basis sets. The study has been focused on the two most stable conformers that are selected after the full geometry optimization of the molecule. A detailed assignment of the FT-IR and FT-Raman spectra has been done for both the conformers along with potential energy distribution for each vibrational mode. The observed and scaled wavenumber of most of the bands has been found to be in good agreement. The UV-Vis spectrum has been recorded and compared with calculated spectrum. In addition, 1H and 13C nuclear magnetic resonance spectra have been also recorded and compared with the calculated data that shows the inter or intramolecular hydrogen bonding. The electronic properties such as HOMO-LUMO energies were calculated by using time-dependent density functional theory. Molecular electrostatic potential has been plotted to elucidate the reactive part of the molecule. Natural bond orbital analysis was performed to investigate the molecular stability. Non linear optical property of the molecule have been studied by calculating the electric dipole moment (?) and the first hyperpolarizability (?) that results in the nonlinearity of the molecule. PMID:24892542

Singh, Swapnil; Singh, Harshita; Srivastava, Anubha; Tandon, Poonam; Sinha, Kirti; Bharti, Purnima; Kumar, Sudhir; Kumar, Padam; Maurya, Rakesh

2014-11-11

166

Progress Towards the Accurate Calculation of Anharmonic Vibrational States of Fluxional Molecules and Clusters Without a Potential Energy Surface  

NASA Astrophysics Data System (ADS)

The accurate calculation of anharmonic vibrational states of highly fluxional systems is complicated by the need to first obtain the full-dimensional potential energy surface(PES). Although commonly exploited as a way around this problem, grid-based methodologies scale exponentially with system size while reduced dimensional approaches are highly system dependent, both in terms of the details of their application and in terms of their suitability. Moreover, the achievement of converged variational calculations of highly anharmonic systems is complicated by the necessity of using a very large basis and hence the construction and diagonalization of enormous Hamiltonian matrices. We report here our recent efforts to develop an algorithm capable of accurately calculating anharmonic vibrational energies, even for very floppy systems, without first obtaining a PES and using only a handful of basis functions per degree of freedom. More specifically, the potential energy and G-matrix elements are calculated on a set of points obtained from a Monte Carlo sampling of the most important regions of configuration space, allowing for a significant reduction in the number of required sampling points. The Hamiltonian matrix is then constructed using an evolving basis which, with each iteration, captures the effect of building H from an ever-expanding basis despite the fact that the actual dimensionality of H is fixed throughout the calculation. This latter property of the algorithm also greatly reduces the size of basis needed for the calculation relative to more traditional variational approaches. The results obtained from the application of our method to several test systems, including ion water complexes, will be reported along with its observed convergence properties.

Petit, Andrew S.; McCoy, Anne B.

2011-06-01

167

Calculation of kinetic energy functions for the ring-twisting and ring-bending vibrations of tetralin and related molecules  

NASA Astrophysics Data System (ADS)

Vector methods have been developed for the computation of the kinetic energy (reciprocal reduced mass) expressions for the ring-twisting and ring-bending vibrations of bicyclic molecules in the tetralin family. The definitions of the bond vectors in terms of these coordinates are presented. Both one- and two-dimensional kinetic energy surfaces have been calculated for tetralin and 1,4-benzodioxan and both are significantly coordinate dependent. The results for the S0 electronic ground states and S1(?, ?*) excited states are presented.

Yang, Juan; Laane, Jaan

2006-10-01

168

Vibrational spectroscopic, first-order hyperpolarizability and HOMO, LUMO studies of 4-chloro-2-(trifluoromethyl) aniline based on DFT calculations  

Microsoft Academic Search

The Fourier-transform infrared and FT-Raman spectra of 4-chloro-2-(trifluoromethyl) aniline (4C2TFA) were recorded in the region 4000–400cm?1 and 3500–50cm?1 respectively. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of 4C2TFA were carried out by density functional theory (DFT\\/B3LYP) method with 6-311+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

M. Arivazhagan; V. P. Subhasini; A. Austine

169

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

170

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

171

SiH stretching frequencies in chlorodisilanes and ab initio calculations of geometry, stretching frequency, vibrational intensity and Mulliken and King effective atomic charges  

NASA Astrophysics Data System (ADS)

Infrared frequencies in the ?SiH region observed in mixtures of chlorodisilanes are assigned by the joint use of substituent effects, determined earlier in Si 2H 5Cl and 1,1-Si 2H 4Cl 2, and ab initio calculations for 1,2-Si 2H 4Cl 2, 1,1,2-Si 2H 3Cl 3 and SiH 3SiCl 3, which together with 1,1,2,2-Si 2H 2Cl 4 were identified as being present. ?SiH frequencies for all the staggered conformers are predicted using harmonic local mode theory. Ab initio geometries were obtained for the above three compounds at the {HF}/{6-31 G?} level, and for both conformers of 1,2-Si 2H 4Cl 2 at {HF}/{tzvp} and {MP2 }/{tzvp} levels. Alpha or gauche chlorine substitution shortens both SiH and SiCl bonds, the former reflecting ?SiH changes. Trans chlorine substitution shortens SiCl bonds slightly, but has no effect on SiH bonds. The local mode behaviour of ?SiH vibrations extends to both infrared and Raman intensities. Ab initio-based atomic polar tensors are used to obtain dipole derivatives, {d? }/{dr }, for the SiH and SiCl bonds and King effective atomic charges, ?, for all atoms. The changes in the latter are compared with changes in the Mulliken atomic charges and a close connection is found in the case of gauche chlorine substitution.

McKean, D. C.; Palmer, M. H.; Guest, M. F.

1996-02-01

172

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

173

Conformational analysis and vibrational study of daidzein by using FT-IR and FT-Raman spectroscopies and DFT calculations.  

PubMed

Daidzein (C15H10O4) is a type of isoflavone. It was isolated from Butea monosperma that belongs to the Fabaceae family. Soybeans and soy products are the abundant source of daidzein. It is the subject of investigation for many reasons, as it has got wide applications, such as anti-tumor, anti-estrogen, weak pro-estrogen and anti-cancer activities. In the present study, a complete vibrational assignment is provided for the observed IR and Raman spectra of daidzein. Electronic properties have been analyzed using TD-DFT method for both gaseous and solvent phase. The optimized geometry, total energy, potential energy surface and vibrational wavenumbers of daidzein have been determined using density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set and a good correlation was found between observed and calculated values. The double well potential energy curve of the molecule about three bonds, has been plotted, as obtained from DFT/6-31G basis. The HOMO-LUMO energy gap of possible conformers has been calculated for comparing their chemical activity. Global reactivity descriptors have been calculated for predicting the chemical reactivity and the stability of chemical systems. Electrostatic potential surface has been plotted for predicting the structure activity relationship. NBO analysis has also been performed to study the stability of the molecule. NLO study reveals the nonlinear properties of the molecule. 1H and 13C NMR spectra have also been studied. Finally, the calculated results were used to simulate infrared and Raman spectra of the title compound which showed a good agreement with the observed spectra. PMID:24211623

Singh, Harshita; Singh, Swapnil; Srivastava, Anubha; Tandon, Poonam; Bharti, Purnima; Kumar, Sudhir; Maurya, Rakesh

2014-01-01

174

Force-field calculation and geometry of the HOOO radical  

NASA Astrophysics Data System (ADS)

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.

Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

2013-09-01

175

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

176

Calculation and analysis of vibrational spectra of adenine–thymine, guanine–cytosine, and adenine–uracil complementary pairs in the condensed state  

Microsoft Academic Search

We have calculated the frequencies of the normal vibrations of the complementary nucleic acid base pairs adenine–thymine,\\u000a guanine–cytosine, adenine–uracil, corresponding to the Watson–Crick structure, and the adenine–uracil pair, corresponding\\u000a to the Hoogsteen structure, in condensed states and we interpret the spectra. We determine the contributions of hydrogen bonds\\u000a to the vibrational modes of the complementary pairs. We have analyzed the

G. N. Ten; T. G. Burova; V. I. Baranov

2009-01-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

178

Ab initio calculations of the elastic, electronic, optical, and vibrational properties of PdGa compound under pressure  

NASA Astrophysics Data System (ADS)

The structural, elastic, electronic, optical, and vibrational properties of cubic PdGa compound are investigated using the norm-conserving pseudopotentials within the local density approximation (LDA) in the framework of the density functional theory. The calculated lattice constant has been compared with the experimental value and has been found to be in good agreement with experimental data. The obtained electronic band structures show that PdGa compound has no band gap. The second-order elastic constants have been calculated, and the other related quantities such as the Young's modulus, shear modulus, Poisson's ratio, anisotropy factor, sound velocities, and Debye temperature have also been estimated. Our calculated results of elastic constants show that this compound is mechanically stable. Furthermore, the real and imaginary parts of the dielectric function and the optical constants such as the electron energy-loss function, the optical dielectric constant and the effective number of electrons per unit cell are calculated and presented in the study. The phonon dispersion curves are also derived using the direct method.

Koc, H.; Yildirim, A.; Deligoz, E.

2012-09-01

179

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

SciTech Connect

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

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

2013-09-21

180

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

PubMed

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

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

2014-01-01

181

Accurate bond dissociation energy of water determined by triple-resonance vibrational spectroscopy and ab initio calculations  

NASA Astrophysics Data System (ADS)

Triple-resonance vibrational spectroscopy is used to determine the lowest dissociation energy, D0, for the water isotopologue HD16O as 41 239.7 ± 0.2 cm-1 and to improve D0 for H216O to 41 145.92 ± 0.12 cm-1. Ab initio calculations including systematic basis set and electron correlation convergence studies, relativistic and Lamb shift effects as well as corrections beyond the Born-Oppenheimer approximation, agree with the measured values to 1 and 2 cm-1 respectively. The improved treatment of high-order correlation terms is key to this high theoretical accuracy. Predicted values for D0 for the other five major water isotopologues are expected to be correct within 1 cm-1.

Boyarkin, Oleg V.; Koshelev, Maxim A.; Aseev, Oleg; Maksyutenko, Pavel; Rizzo, Thomas R.; Zobov, Nikolay F.; Lodi, Lorenzo; Tennyson, Jonathan; Polyansky, Oleg L.

2013-05-01

182

HO2 ro-vibrational bound-state calculations for large angular momentum: J = 30, 40, and 50.  

PubMed

The Lanczos homogeneous filter diagonalization method and the real Chebyshev filter diagonalization scheme incorporating doubling of the autocorrelation functions have been employed to compute the HO2 ro-vibrational states for high total angular momenta, J = 30, 40, and 50. For such computationally challenging calculations, we have adopted a parallel computing strategy to perform the matrix-vector multiplications. Low-lying bound states and high-lying bound states close to the dissociation threshold are reported. For low-lying bound states, a spectroscopic assignment has been attempted and the widely used approximate J-shifting method has been tested for this deep-well system. For high-lying bound states, the attempted spectroscopic assignments as well as the J-shifting approximation fail because of very strong Coriolis mixing, indicating that the Coriolis couplings are important for this system. PMID:16509649

Zhang, Hong; Smith, Sean C

2006-03-01

183

Calculation of Spectra of the Lattice and Surface Vibrations of Organic Nano-Crystals  

E-print Network

Calculations of frequencies of the lattice and surface oscillations of organic nano-crystals are carried out. As the sample the para-dichlorobenzol has been chosen. Change of spectra of oscillations from the sizes of nano-particles is found. It is shown that with the reduction of the sizes of nano-particles a spectrum of the surface oscillations prevailing. Calculations have shown that for the correct interpretation of the observational spectra it is necessary to consider orientation disorder of the surface molecules and presence of vacancies in nano-particle volume.

M. A. Korshunov

2007-09-18

184

Calculation of the transitions in the amine inversion vibration of some local anesthetics  

NASA Astrophysics Data System (ADS)

In the para-amino group of the local anesthetics benzocaine, procaine and procaine hydrochloride, the potential function of inversion, the barrier height V? i and the optimum ? o inversion angle have been determinated. Two methods are shown for calculating transitions based on the two frequencies of inversion which easily can be detected in the infrared absorption and Raman spectra in solid compounds. Also the frequencies associated with tra nsitions are able to be obtained.

Alcolea Palafox, M.

1988-05-01

185

Vibrational spectroscopy of beryllium aluminosilicates: Heat capacity calculations from band assignments  

Microsoft Academic Search

Far-infrared, mid-IR, and Raman powder spectra were measured on six phases (bromellite, chrysoberyl, phenakite, bertrandite, beryl, and euclase) in the system BeO-Al2O3-SiO2-H2O. A single-crystal absorption spectrum of IR fundamentals in beryl is also presented, which more closely resembles the powder absorption spectrum than it does absorption spectra calculated from single-crystal reflection data.

A. M. Hofmeister; T. C. Hoering; D. Virgo

1987-01-01

186

Infrared and Raman spectra, conformational stability, ab initio calculations of structure, and vibrational assignment of ethynylmethyl cyclobutane  

NASA Astrophysics Data System (ADS)

The infrared spectra (3200-300 cm -1) of the gas and solid and the Raman spectra (3200-30 cm -1) of the liquid with quantitative depolarization values and the solid have been recorded of ethynylmethyl cyclobutane (cyclobutylmethyl acetylene), c-C 4H 7CH 2C?CH. Both the equatorial and the axial conformers have been identified in the fluid phases and both the gauche and trans conformations of the methyl acetylenic group have been identified for each ring conformer. Variable temperature (-105 to -150°C) studies of the infrared spectra of the sample dissolved in liquid krypton have been carried out. From these data the enthalpy differences have been determined to the 112±11 cm -1 (1.34±0.13 kJ/mol) between the most stable equatorial- trans (Et) conformer and the equatorial- gauche (Eg) conformer which is the second most stable conformer and 327±35 cm -1 (3.91±0.42 kJ/mol) with the axial- gauche (Ag) conformer which is the least stable conformer. The enthalpy difference between the axial- trans (At) and the equatorial- gauche(Eg) is 56±6 cm -1. At ambient temperature there is approximately 33% of the Et conformer, 38% of the Eg form, 15% of the At and 14% of the Ag conformer. For the polycrystalline solid the Eg conformer is the only form present which probably results form the packing in the crystal. A complete vibrational assignment is proposed for both equatorial conformers and additionally a few of the fundamentals of the At and Ag conformers have been assigned. The vibrational assignments are supported by normal coordinate calculations utilizing the force constants from ab initio MP2/6-31G(d) calculations. Complete equilibrium geometries have been determined for all four possible rotamers by ab initio calculations employing the 6-31G(d) and 6-311++G(d,p) basis sets at levels of restricted Hartree-Fock (RHF) and /or Moller-Plesset (MP2) with full electron correlation by the perturbation method to second order. The results are discussed and compared to those obtained for some similar molecules.

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

2002-01-01

187

Calculating vibrational spectra with sum of product basis functions without storing full-dimensional vectors or matrices  

E-print Network

We propose an iterative method for computing vibrational spectra that significantly reduces the memory cost of calculations. It uses a direct product primitive basis, but does not require storing vectors with as many components as there are product basis functions. Wavefunctions are represented in a basis each of whose functions is a sum of products (SOP) and the factorizable structure of the Hamiltonian is exploited. If the factors of the SOP basis functions are properly chosen, wavefunctions are linear combinations of a small number of SOP basis functions. The SOP basis functions are generated using a shifted block power method. The factors are refined with a rank reduction algorithm to cap the number of terms in a SOP basis function. The ideas are tested on a 20-D model Hamiltonian and a realistic CH$_3$CN (12 dimensional) potential. For the 20-D problem, to use a standard direct product iterative approach one would need to store vectors with about $10^{20}$ components and would hence require about $8 \\times 10^{11}$ GB. With the approach of this paper only 1 GB of memory is necessary. Results for CH$_3$CN agree well with those of a previous calculation on the same potential.

Arnaud Leclerc; Tucker Carrington

2014-05-12

188

Coupled rotor-body vibrations with inplane degrees of freedom  

NASA Technical Reports Server (NTRS)

In an effort to understand the vibration mechanisms of helicopters, the following basic studies are considered. A coupled rotor-fuselage vibration analysis including inplane degrees of freedom of both rotor and airframe is performed by matching of rotor and fuselage impedances at the hub. A rigid blade model including hub motion is used to set up the rotor flaplag equations. For the airframe, 9 degrees of freedom and hub offsets are used. The equations are solved by harmonic balance. For a 4-bladed rotor, the coupled responses and hub loads are calculated for various parameters in forward flight. The results show that the addition of inplane degrees of freedom does not significantly affect the vertical vibrations for the cases considered, and that inplane vibrations have similar resonance trends as do flapping vibrations.

Ming-Sheng, H.; Peters, D. A.

1985-01-01

189

Torque and efficiency calculation of an interior permanent magnet motor considering harmonic iron losses of both the stator and rotor  

Microsoft Academic Search

A method to estimate characteristics of interior permanent magnet motors considering effects of iron loss is introduced. The equivalent circuit parameters including the iron loss resistance are calculated as functions of d-q axis currents by the finite-element method with the consideration of movement of the rotor. The characteristics of the motor are calculated from the equivalent circuit. By using this

Katsumi Yamazaki

2003-01-01

190

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

191

Intramolecular Dynamics Probed using High Harmonic Generation  

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

192

Interpretation of resonance cars and shpolskii spectra with calculated molecular geometries, vibrational frequencies and relative intensities: Chrysene in it's lowest excited singlet and triplet state  

NASA Astrophysics Data System (ADS)

Coherent anti-Stokes Raman scattering (CARS) spectra of excited molecules as well as Shpolskii spectra provide information about geometry changes between ground and excited states. Vibrational frequencies and relative intensities from recently obtained CARS spectra of the chrysene S 1 and T 1 state and earlier observed Shpolskii spectra are interpreted in terms of molecular geometry and force-field changes by means of quantum-chemical consistent force field (QCFF) and Franck-Condon factor calculations. The comparison of observed and calculated relative intensities indicates a coupling between the S 1 and S 2 state enhancing some of the vibrational radiative singlet transitions both in absorption and fluorescence spectra whereas within the phosphorescence spectra proportionality to calculated Franck-Condon factors is obeyed. The T 1 state is the more loosely bound state and its geometry change is different from that of the S 1 state. The resonance CARS transitions in the S 1 state are assigned to totally symmetric vibrations getting their intensity by a coupling scheme analogous to the A term of the resonance Raman effect: the relative intensity of a transition is shown to be proportional to the Franck-Condon factor to the higher excited state and to the squared vibrational frequency. Using this relation this state can be identified by means of its finger-print-like intensity pattern.

Jung, Ch.; Lau, A.; Weigmann, H.-J.; Werncke, W.; Pfeiffer, M.

1982-11-01

193

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

194

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 Møller-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

195

Infrared and Raman spectra, conformational stability, ab initio calculations of structure and vibrational assignment of 4-fluoro-1-pentyne  

NASA Astrophysics Data System (ADS)

The infrared spectra (3500-50 cm -1) of the gas and solid and the Raman spectra (3500-50 cm -1) of the liquid and solid have been recorded for 4-fluoro-1-pentyne, HC?CCH 2C(H)FCH 3. All three expected conformers ( F-trans, H-trans and Me-trans corresponding to the fluorine atom, hydrogen atom, and methyl group, trans to triple bond) have been identified in the fluid phases. Variable temperature studies of the infrared spectra (3500-400 cm -1) of the sample dissolved in liquid krypton (-105 to -135 °C) have been recorded. Utilizing six sets of conformer pairs, the enthalpy differences have been determined to be 129±13 cm -1 (1.54±0.16 kJ/mol) between the most stable conformer, the F-trans form, and the one of intermediate stability, the H-trans form and 178±18 cm -1 (2.13±0.21 kJ/mol) between the F-trans form and the Me-trans conformer, the least stable form. At ambient temperature there is approximately 51% of the F-trans conformer, 27% of the H-trans conformer, and 22% of the Me-trans form present in the vapor state. In the polycrystalline state, the most stable conformer is the one with the hydrogen atom trans to the triple bond which is believed to result from crystal packing factors. Complete vibrational assignments are proposed for all three conformers based on infrared contours, relative intensities, depolarization values and group frequencies which are supported by the normal coordinate calculations utilizing the force constants from the ab initio MP2/6-31G(d) calculations. Complete equilibrium geometries have been determined for both rotamers by ab initio calculations employing a variety of basis sets at the level of Moller-Plesset with full electron correlation by the perturbation method to the second order (MP2) and by density functional theory utilizing the B3LYP method. From all of these calculations the F-trans conformer is predicted to be the most stable form, but the energy difference is significantly higher than the experimentally determined enthalpy difference. The results are discussed and compared to the corresponding quantities to those obtained for some similar molecules.

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

2003-09-01

196

Molecular conformational analysis, vibrational spectra, NBO analysis and first hyperpolarizability of (2E)-3-phenylprop-2-enoic anhydride based on density functional theory calculations.  

PubMed

The conformational behavior and structural stability of (2E)-3-phenylprop-2-enoic anhydride were investigated by using density functional theory. Seventeen possible stable conformations of the title compound were determined and verified with their calculated vibrational frequencies being all positive. The optimized molecular structure, vibrational wavenumbers, corresponding vibrational assignments of (2E)-3-phenylprop-2-enoic anhydride have been investigated experimentally and theoretically using Gaussian09 software package. Potential energy distribution of normal modes vibrations was done using GAR2PED program. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated first hyperpolarizability of the title compound is 12×10(-30) esu and is 92.31 times that of the standard NLO material urea and the title compound is an attractive object for future studies of nonlinear optical properties. MEP was performed by the DFT method and the predicted infrared intensities and Raman activities have also been reported. PMID:24704480

Sheena Mary, Y; Raju, K; Panicker, C Yohannan; Al-Saadi, Abdulaziz A; Thiemann, Thies; Van Alsenoy, Christian

2014-07-15

197

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

NASA Astrophysics Data System (ADS)

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.

Petrenko, Taras; Neese, Frank

2012-12-01

198

Hybrid MP2/MP4 potential surfaces in VSCF calculations of IR spectra: applications for organic molecules.  

PubMed

This study introduces an improved hybrid MP2/MP4 ab initio potential for vibrational spectroscopy calculations which is very accurate, yet without high computational demands. The method uses harmonic vibrational calculations with the MP4(SDQ) potential to construct an improved MP2 potential by coordinate scaling. This improved MP2 potential is used for the anharmonic VSCF calculation. The method was tested spectroscopically for four molecules: butane, acetone, ethylene and glycine. Very good agreement with experiment was found. For most of the systems, the more accurate harmonic treatment considerably improved the MP2 anharmonic results. PMID:23838574

Knaanie, Roie; Šebek, Ji?í; Kalinowski, Jaroslaw; Benny Gerber, R

2014-02-01

199

Molecular structure, vibrational spectra and HOMO, LUMO analysis of yohimbine hydrochloride by density functional theory and ab initio Hartree-Fock calculations  

NASA Astrophysics Data System (ADS)

Yohimbine hydrochloride (YHCl) is an aphrodisiac and promoted for erectile dysfunction, weight loss and depression. The optimized geometry, total energy, potential energy surface and vibrational wavenumbers of yohimbine hydrochloride have been determined using ab initio, Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set. A complete vibrational assignment is provided for the observed Raman and IR spectra of YHCl. The UV absorption spectrum was examined in ethanol solvent and compared with the calculated one in gas phase as well as in solvent environment (polarizable continuum model, PCM) using TD-DFT/6-31G basis set. These methods are proposed as a tool to be applied in the structural characterization of YHCl. The calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) with frontier orbital gap are presented.

Joshi, Bhawani Datt; Srivastava, Anubha; Tandon, Poonam; Jain, Sudha

2011-11-01

200

Structure, vibrational analysis, and insights into host-guest interactions in as-synthesized pure silica ITQ-12 zeolite by periodic B3LYP calculations.  

PubMed

As-made and calcined ITQ-12 zeolites are structurally characterized by means of the analysis of their vibrational modes. The experimental IR spectra made on high crystalline samples are compared with accurate B3LYP periodic calculations performed with the CRYSTAL06 code. The fair agreement between both sets of data allows us to make a reliable assignment of the IR modes. Thanks to the detailed information provided by the theoretical calculations, the analysis of the IR intensities, the Born dynamic charges, and the whole set of vibrational frequencies at Gamma-point shed light on several aspects of the host-guest interaction, structure-direction issues, including the role of fluoride anions in allowing the crystallization of silica structures with strained double-four rings, and the role played by the framework flexibility. PMID:17718565

Zicovich-Wilson, Claudio Marcelo; San-Román, María Luisa; Camblor, Miguel Angel; Pascale, Fabien; Durand-Niconoff, José Sergio

2007-09-19

201

Application of the Method of Stein and Sanders to the Calculation of Vibration Characteristics of a 45 deg Delta-Wing Specimen  

NASA Technical Reports Server (NTRS)

Generalized influence coefficients are calculated by the method of NACA TN 3640 for a large-scale, built-up, 450 delta-wing specimen. These are used together with appropriate generalized masses to obtain the natural modes and frequencies in symmetric and antisymmetric free-free vibration. The resulting frequencies are compared with those obtained experimentally and are found to be consistently high. Possible sources of the disparities are discussed.

Hedgepeth, John M.; Warner, Paul G., Jr.

1959-01-01

202

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

Microsoft Academic Search

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

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

2012-01-01

203

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

NASA Astrophysics Data System (ADS)

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

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

204

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

PubMed

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

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

2014-05-01

205

Experimental and theoretical study of the vibrational spectra of halothane  

NASA Astrophysics Data System (ADS)

MP2 and B3LYP calculations carried out with the 6-311++G(df,pd) basis set show that the staggered structure of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) is more stable than the eclipsed one. Results of natural bond orbital calculations for both structures are discussed. The experimental IR and Raman spectra of halothane pure and dissolved in carbon tetrachloride are investigated. The harmonic vibrational frequencies, and IR and Raman intensities are calculated with the B3LYP method using the same basis set. The detailed assignment of the fundamental vibrations of halothane is made on the basis of the calculated potential energy distribution, PED. The near-IR spectra are investigated between 4000 and 9000 cm -1. The frequencies of the fundamental, first and second overtone have allowed us to estimate the anharmonicity constants of the ?(CH) stretching vibration. The frequency of this vibration corrected for anharmonicity is in good agreement with the B3LYP one. The experimental spectra show that the ?(CH) vibration of halothane, in complexes with acetone or dioxane, is red-shifted by a few wavenumbers. Complex formation increases the anharmonicity of the ?(CH) vibration.

Czarnik-Matusewicz, B.; Michalska, D.; Sandorfy, C.; Zeegers-Huyskens, Th.

2006-03-01

206

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

207

Structural and vibrational study of maprotiline  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

208

MULTIMODE quantum calculations of vibrational energies and IR spectrum of the NO+(H2O) cluster using accurate potential energy and dipole moment surfaces  

NASA Astrophysics Data System (ADS)

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

Homayoon, Zahra

2014-09-01

209

MULTIMODE quantum calculations of vibrational energies and IR spectrum of the NO(+)(H2O) cluster using accurate potential energy and dipole moment surfaces.  

PubMed

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

Homayoon, Zahra

2014-09-28

210

Experimental determinations and quantum-chemical calculations of the vibrational spectra of ?-ZnB4O7 and ?-CaB4O7  

NASA Astrophysics Data System (ADS)

The two oxoborates ?-ZnB4O7 and ?-CaB4O7 were synthesized and investigated by FTIR- and Raman spectroscopy and ab initio quantum chemical calculations. Maximum and mean deviations between experimentally determined bands and calculated modes ranged between 15-36 cm-1 and 5-7 cm-1, respectively, allowing band assignments to vibrational modes in most cases. The complex network structures with tetrahedral BO4 and planar OB3 groups are mirrored by the spectra and numerous vibrational modes, not assignable by standard borates classification schemes. It was confirmed that OB3 units, despite similar force constants and geometry, do not absorb in the same range as BO3 units. Bands in the high wavenumber range are rather caused by B-O-(Zn/Ca), O-B-O, B-O-B, and B-O stretching and bending vibrations. The experimental observation of inactive or Raman-active modes in the absorption spectra indicates defects or structural distortions in both compounds.

Kaindl, Reinhard; Sohr, Gerhard; Huppertz, Hubert

2013-12-01

211

The librational and vibrational spectra of water in natrolite, Na 2Al 2Si 3O 10·2H 2O compared with ab-initio calculations  

NASA Astrophysics Data System (ADS)

The librational spectrum of water in natrolite at 25 K is presented for the first time, and experimental results as obtained by inelastic neutron scattering and IR are compared with theoretical ab-initio calculations of a 2Na-H 2O cluster alone. Calculations using various basis sets show the necessity for augmented basis sets in the determination of the librational frequencies. The experimental librational frequencies are 517, 557 and 701 cm -1 and the theoretical frequencies obtained for the 6-311G**(2d,2p), with MP2 electron correlation, are 460.8, 508.7 and 669.4 cm -1 for rocking, twisting and wagging, respectively. The calculated frequencies are approximately stable above the 6-31G* level. We also consider the anharmonicity of the energy well, and show that the harmonic approximation is valid to 2% in the frequency. We then consider a harmonic model of hydrogen bonding accounting for the observed structure and show this to be incompatible with the observed frequencies.

Line, Christina M. B.; Kearley, G. J.

1998-08-01

212

High-precision nonadiabatic calculations of dynamic polarizabilities and hyperpolarizabilities for the lowlying vibrational-rotational states of hydrogen molecular ions  

E-print Network

The static and dynamic electric multipolar polarizabilities and second hyperpolarizabilities of the H$_2^+$, D$_2^+$, and HD$^+$ molecular ions in the ground and first excited states are calculated nonrelativistically using explicitly correlated Hylleraas basis sets. The calculations are fully nonadiabatic; the Born-Oppenheimer approximation is not used. Comparisons are made with published theoretical and experimental results, where available. In our approach, no derivatives of energy functions nor derivatives of response functions are needed. In particular, we make contact with earlier calculations in the Born-Oppenheimer calculation where polarizabilities were decomposed into electronic, vibrational, and rotational contributions and where hyperpolarizabilities were determined from derivatives of energy functions. We find that the static hyperpolarizability for the ground state of HD$^+$ is seven orders of magnitude larger than the corresponding dipole polarizability. For the dipole polarizability of HD$^+$ ...

Tang, Li-Yan; Shi, Ting-Yun; Babb, James F

2014-01-01

213

Molecular conformational analysis, vibrational spectra, NBO analysis and first hyperpolarizability of (2E)-3-(3-chlorophenyl)prop-2-enoic anhydride based on density functional theory calculations  

NASA Astrophysics Data System (ADS)

The conformational behavior and structural stability of (2E)-3-(3-chlorophenyl)prop-2-enoic anhydride were investigated by using density functional theory. The optimized molecular structure, vibrational wavenumbers, corresponding vibrational assignments of (2E)-3-(3-chlorophenyl)prop-2-enoic anhydride have been investigated experimentally and theoretically. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. The stability of the molecule arising from hyperconjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated first hyperpolarizability of the title compound is 15.8 × 10-30esu, and is 121.54 times that of the standard NLO material urea and the title compound is an attractive object for future studies of nonlinear optical properties. MEP was performed by the DFT method and the predicted infrared intensities and Raman activities have also been reported.

Mary, Y. Sheena; Raju, K.; Panicker, C. Yohannan; Al-Saadi, Abdulaziz A.; Thiemann, Thies

2014-10-01

214

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* were compared with the experimental data. It is remarkable that the SVWN/6-311++G and SVWN/6-311+G* 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

215

Characterization of 1,5-dimethoxynaphthalene by vibrational spectroscopy (FT-IR and FT-Raman) and density functional theory calculations.  

PubMed

In this work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and natural bond orbital (NBO) analysis of 1,5-dimethoxynaphthalene. The optimized molecular structure, atomic charges, vibrational frequencies and natural bond orbital analysis of 1,5-dimethoxynaphthalene have been studied by performing DFT/B3LYP/6-31G(d,p) level of theory. The FTIR, FT-Raman spectra were recorded in the region of 4000-400cm(-)(1) and 3500-50cm(-)(1) respectively. The scaled wavenumbers are compared with the experimental values. The difference between the observed and scaled wavenumber values of the most fundamentals is very small. The formation of hydrogen bond was investigated in terms of the charge density by the NBO analysis. Natural Population Analysis (NPA) was used for charge determination in the title molecule. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations. PMID:25014641

Kandasamy, M; Velraj, G; Kalaichelvan, S; Mariappan, G

2015-01-01

216

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

217

Harmonic spinors on Riemann surfaces  

Microsoft Academic Search

We calculate the dimension of the space of harmonic spinors on hyperelliptic Riemann surfaces for all spin structures. Furthermore, we present non-hype relliptic examples of genus 4 and 6 on which the maximal possible number of linearly independent harmonic spinors is achieved.

Christian Bär; Paul Schmutz

1992-01-01

218

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

219

Simulation of Payload Vibration Protection by Shape Memory Alloy Parts  

NASA Astrophysics Data System (ADS)

A system of vibroisolation under consideration consists of a payload connected to a vibrating housing by plane shape memory alloy (SMA) slotted elements. The calculation of the mechanical behavior of the SMA is based on a microstructural theory. Simulations of harmonic and of impact excitations are carried out. The results have shown that protective properties of this system depend on the SMA state. The maximum reduction of the acceleration amplitude for harmonic excitation is reached when the SMA is in the martensitic (pseudo-plastic) state or in the two-phase state. A variation of temperature allows changing the resonance frequency and thus escaping from the resonance and controlling a mode of vibration.

Volkov, Aleksandr E.; Evard, Margarita E.; Red'kina, Kristina V.; Vikulenkov, Andrey V.; Makarov, Vyacheslav P.; Moisheev, Aleksandr A.; Markachev, Nikolay A.; Uspenskiy, Evgeniy S.

2014-07-01

220

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

Microsoft Academic Search

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

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

2008-01-01

221

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

222

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

223

The fictitious force method for efficient calculation of vibration from a tunnel embedded in a multi-layered half-space  

NASA Astrophysics Data System (ADS)

This paper presents an extension of the Pipe-in-Pipe (PiP) model for calculating vibrations from underground railways that allows for the incorporation of a multi-layered half-space geometry. The model is based on the assumption that the tunnel displacement is not influenced by the existence of a free surface or ground layers. The displacement at the tunnel-soil interface is calculated using a model of a tunnel embedded in a full space with soil properties corresponding to the soil in contact with the tunnel. Next, a full space model is used to determine the equivalent loads that produce the same displacements at the tunnel-soil interface. The soil displacements are calculated by multiplying these equivalent loads by Green's functions for a layered half-space. The results and the computation time of the proposed model are compared with those of an alternative coupled finite element-boundary element model that accounts for a tunnel embedded in a multi-layered half-space. While the overall response of the multi-layered half-space is well predicted, spatial shifts in the interference patterns are observed that result from the superposition of direct waves and waves reflected on the free surface and layer interfaces. The proposed model is much faster and can be run on a personal computer with much less use of memory. Therefore, it is a promising design tool to predict vibration from underground tunnels and to assess the performance of vibration countermeasures in an early design stage.

Hussein, M. F. M.; François, S.; Schevenels, M.; Hunt, H. E. M.; Talbot, J. P.; Degrande, G.

2014-12-01

224

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

PubMed

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

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

2015-01-25

225

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

NASA Technical Reports Server (NTRS)

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

Bielawa, R. L.

1984-01-01

226

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

NASA Astrophysics Data System (ADS)

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).

Marchewka, M. K.; Drozd, M.

2012-12-01

227

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

2012-12-01

228

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

NASA Astrophysics Data System (ADS)

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

Kouach-Alix, I.; Vergoten, G.

1994-07-01

229

FEMVib, an ab initio multi-dimensional solver for probing vibrational dynamics in polyatomic molecules and free radicals  

NASA Astrophysics Data System (ADS)

Accurate prediction of the vibrational spectra in polyatomic molecules and free radicals depends on obtaining high quality solutions to the vibrational Schrodinger equation. The quantum simple harmonic oscillator provides the traditional first approximation for modeling molecular vibrational states. Rarely does a vibrational analysis extend beyond this first approximation, and harmonic energy levels are routinely used to predict the infrared spectra and other dynamical properties of molecules. However, there are many large-amplitude molecular motions that are extremely anharmonic, including internal torsions about atom-atom single bonds, bending and stretching of weak bonds in van der Waals complexes, and isomerization along relocalization coordinates in free radicals. In these cases, the harmonic treatment provided by electronic structure quantum chemistry packages is completely inadequate. Furthermore, the anharmonicity often includes strong coupling among two or more distinct vibrational coordinates, necessitating a multi-dimensional analysis of the vibrational Schrodinger equation along the coupled coordinates. A novel ab initio solver package, FEMVib, is developed within the finite element method (FEM) framework. A mixed programming paradigm that combines C++, Fortran and Python is employed to take advantage of existing numerical libraries. FEMVib has been rigorously tested to resolve the eigenvalues and wavefunctions of hundreds of vibrational energy states to high accuracy and precision. It may be used to calculate the complete vibrational spectra of triatomic molecules or to approximate larger systems through a "relaxed" model that allows complete coupling of up to three selected vibrational coordinates. FEMVib provides physical chemists with a general, robust and accurate computational tool for molecular vibrational analysis.

Xu, Dong

230

Molecular orbital calculations on the vibrational spectra of Q 3 T-(OH) species and the hydrolysis of a three-membered aluminosilicate ring  

NASA Astrophysics Data System (ADS)

Force constant analyses of the molecules [(H 3SiO) 3Al-(OH)] 1-, Na +[(H 3SiO) 3Al-(OH)] 1-, [((OH) 3SiO) 3Al-(OH)] 1- [(H 3SiO) 3Si-(OH)],[((OH) 3SiO) 3Si-(OH)],[((OH) 3SiO) 2((OH) 3A10)Si(OH)] 1- and Na + [(H 3SiO ) 2 (H 3Al0) Si- (OH)] 1- have been performed with ab initio molecular orbital calculations to determine the frequencies and H-D shifts of T- (OH) vibrations in Q 3 T- (OH) species where T is a So 4+ or Al 3+. Calculated Q 3 Si-(OH) vibrations are close to the observed value in H 2O-bearing Si0 2 glass. The theoretical Al-(OH) stretching frequency in Na +[ (H 3SiO) 3A1-(OH)] 1- matches the 880 cm - shoulder in the vibrational spectra of hydrous albitic glasses within experimental error. Isotopic substitution of deuterium for hydrogen in the T-(OH) bond results in frequency shifts of less than 25 cm -1 in all cases consistent with the small H-D frequency shifts observed in silica (Mysen and Virgo, 1986) and Na-aluminosilicate glasses (McMillan et al., 1993). Hydrolysis of a three-membered aluminosilicate ring into a trimeric chain (i.e., [H 6SiAl 20 9] 2- + H 2O ? [H 8SiAl 20 10] 2-) was also calculated. Hydrolysis occurs through a pentavalent Al 3+ transition state complex. Calculated energies of the reactants and product in the above reaction predict that the chain configuration is in a marginally lower potential energy state (-36 kJ/mol) than the H 2O-ring dimer. An activation energy of + 171 kJ/mol is predicted between the two species for hydrolysis and +207 kJ/mol for the reverse reaction.

Kubicki, J. D.; Sykes, Dan

1995-12-01

231

Conformational analysis and vibrational spectroscopic studies on dapsone  

NASA Astrophysics Data System (ADS)

In this study, the theoretical conformation analysis of free dapsone has been performed by single point energy calculations at both semi-empirical PM3 and DFT/B3LYP-3-21G theory levels and three stable conformers were determined. Both the IR and Raman spectra of the molecule in solid phase have been recorded. The IR intensities and harmonic vibrational wavenumbers of each conformer were calculated by DFT method at B3LYP/6-31++G(d,p) theory level. For the fundamental characterization, the total energy distribution (TED) calculations of the vibrational modes were done using parallel quantum mechanic solution program (SQM) and the fundamental modes were assigned. The theoretical results are in agreement with the experimental ones.

Ildiz, Gulce Ogruc; Akyuz, Sevim

2012-11-01

232

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

233

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

234

Molecular structure of the trans and cis isomers of metal-free phthalocyanine studied by gas-phase electron diffraction and high-level quantum chemical calculations: NH tautomerization and calculated vibrational frequencies.  

PubMed

The molecular structure of the trans isomer of metal-free phthalocyanine (H2Pc) is determined using the gas electron diffraction (GED) method and high-level quantum chemical calculations. B3LYP calculations employing the basis sets 6-31G**, 6-311++G**, and cc-pVTZ give two tautomeric isomers for the inner H atoms, a trans isomer having D2h symmetry and a cis isomer having C2v symmetry. The trans isomer is calculated to be 41.6 (B3LYP/6-311++G**, zero-point corrected) and 37.3 kJ/mol (B3LYP/cc-pVTZ, not zero-point corrected) more stable than the cis isomer. However, Hartree-Fock (HF) calculations using different basis sets predict that cis is preferred and that trans does not exist as a stable form of the molecule. The equilibrium composition in the gas phase at 471 degrees C (the temperature of the GED experiment) calculated at the B3LYP/6-311++G** level is 99.8% trans and 0.2% cis. This is in very good agreement with the GED data, which indicate that the mole fraction of the cis isomer is close to zero. The transition states for two mechanisms of the NH tautomerization have been characterized. A concerted mechanism where the two H atoms move simultaneously yields a transition state of D2h symmetry and an energy barrier of 95.8 kJ/mol. A two-step mechanism where a trans isomer is converted to a cis isomer, which is converted into another trans isomer, proceeds via two transition states of C(s) symmetry and an energy barrier of 64.2 kJ/mol according to the B3LYP/6-311++G** calculation. The molecular geometry determined from GED is in very good agreement with the geometry obtained from the quantum chemical calculations. Vibrational frequencies, IR, and Raman intensities have been calculated using B3LYP/6-311++G**. These calculations indicate that the molecule is rather flexible with six vibrational frequencies in the range of 20-84 cm(-1) for the trans isomer. The cis isomer might be detected by infrared matrix spectroscopy since the N-H stretching frequencies are very different for the two isomers. PMID:18457372

Strenalyuk, Tatyana; Samdal, Svein; Volden, Hans Vidar

2008-05-29

235

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

236

FEMVib, an ab initio multi-dimensional solver for probing vibrational dynamics in polyatomic molecules and free radicals  

Microsoft Academic Search

Accurate prediction of the vibrational spectra in polyatomic molecules and free radicals depends on obtaining high quality solutions to the vibrational Schrodinger equation. The quantum simple harmonic oscillator provides the traditional first approximation for modeling molecular vibrational states. Rarely does a vibrational analysis extend beyond this first approximation, and harmonic energy levels are routinely used to predict the infrared spectra

Dong Xu

2008-01-01

237

Harmonic engine  

SciTech Connect

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

238

Molecular and vibrational structure of 2-mercapto pyrimidine and 2,4-diamino-6-hydroxy-5-nitroso pyrimidine: FT-IR, FT-Raman and quantum chemical calculations.  

PubMed

The molecular vibrations of 2-mercapto pyrimidine (MP) and 2,4-diamino-6-hydroxy-5-nitroso pyrimidine (DAHNP) were investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopics. In parallel, ab initio and various density functional (DFT) methods were used to determine the geometrical, energetic and vibrational characteristics of MP and DAHNP. On the basis of B3LYP/6-31G* and B3LYP/6-311+G** methods and basis set combinations, a normal mode analysis was performed to assign the various fundamental frequencies according to the total energy distribution (TED). Simulation of infrared and Raman spectra, utilizing the results of these calculations led to excellent overall agreement with observed spectral patterns. The scaled quantum mechanical (SQM) approach applying selective scaling of the DFT force fields was shown to be superior to the scaling method in its ability to ensure correct band assignments and successful simulation of IR and Raman spectra including band polarisations and intensity patterns. PMID:15990356

Krishnakumar, V; John Xavier, R

2006-02-01

239

Vibrational spectroscopic (FT-IR, FT-Raman) and quantum chemical calculations of 1-(5,5-dioxido-10H-phenothiazin-10-yl)ethanone.  

PubMed

FT-IR and FT-Raman spectra of 1-(5,5-dioxido-10H-phenothiazin-10-yl)ethanone were recorded and analyzed. The vibrational wavenumbers were computed using B3LYP/6-31G? and SDD basis. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using NBO analysis. Molecular electrostatic potential was performed by the DFT method and infrared intensities and Raman activities are also reported. MEP shows that the negative potential sites are on oxygen atoms and the positive potential sites are around the nitrogen atoms. The geometrical parameters of the title compound (SDD) are in agreement with XRD crystal structure data. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of nonlinear optics. PMID:24211803

Kaur, Manpreet; Mary, Y Shyma; Panicker, C Yohannan; Varghese, Hema Tresa; Yathirajan, H S; Byrappa, K; Van Alsenoy, Christian

2014-01-01

240

Anharmonic vibrations of the dicarbon antisite defect in 4H-SiC  

SciTech Connect

Dicarbon antisite defects were created by either electron irradiation or ion implantation into 4H-SiC. The no-phonon lines from the dicarbon antisite defect center were observed with their phonon replicas. The stretch frequencies of the defect were observed up to the fifth harmonic. The Morse potential model accounts for the anharmonicity quite well and gives a very good prediction of the vibration energies up to the fifth harmonic with an error of less than 1%. First principles calculations show that the model of a dicarbon antisite defect along with its four nearest neighboring carbon atoms can explain the observed anharmonicity.

Yan, F.; Devaty, R. P.; Choyke, W. J. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Gali, A. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Kimoto, T. [Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510 (Japan); Ohshima, T. [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Pensl, G. [Lehrstuhl fuer Angewandte Physik, Universitaet Erlangen-Nuernberg, Staudstr. 7/A3 Erlangen (Germany)

2012-03-26

241

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

PubMed

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

Luo, Ye; Zen, Andrea; Sorella, Sandro

2014-11-21

242

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

243

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

244

Calculation of the vibrational excited states of malonaldehyde and their tunneling splittings with the multi-configuration time-dependent Hartree method  

NASA Astrophysics Data System (ADS)

We report energies and tunneling splittings of vibrational excited states of malonaldehyde which have been obtained using full dimensional quantum mechanical calculations. To this end we employed the multi configuration time-dependent Hartree method. The results have been obtained using a recently published potential energy surface [Y. Wang, B. J. Braams, J. M. Bowman, S. Carter, and D. P. Tew, J. Chem. Phys. 128, 224314 (2008)] which has been brought into a suitable form by a modified version of the n-mode representation which was used with two different arrangements of coordinates. The relevant terms of the expansion have been identified with a Metropolis algorithm and a diffusion Monte-Carlo technique, respectively.

Schröder, Markus; Meyer, Hans-Dieter

2014-07-01

245

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

246

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

PubMed

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

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

2014-12-10

247

Calculations of the dynamics of phase-locked vibrational wave packets in Na2+: Young's double slit experiment in a molecule  

Microsoft Academic Search

The formation of specific target states in Na2+ is investigated using phase-locked femtosecond pulse sequences. The pulse sequences generate customized vibrational wave packets whose motion can be interpreted using classical physics. It is shown that, if two vibrational wave packets are initially excited at either end of the vibrational coordinate, changing the initial phase difference between them can have a

V. G. Stavros; H. H. Fielding

2000-01-01

248

Correlated ab initio harmonic frequencies and infrared intensities for furan, pyrrole, and thiophene  

SciTech Connect

Equilibrium geometries, harmonic vibrational frequencies, and infrared intensities are calculated analytically at the second-order Moeller-Plesset level (MP2) with a DZP basis for the five-membered heterocyclic aromatics furan, pyrrole, and thiophene. The results are of an accuracy to show up misassignments in the original experimental interpretation of the spectra. They also give confidence that ab initio calculations including electron correlation and using flexible basis sets can describe accurately the quadratic part of the potential energy surface. For such systems, these ab initio studies will aid the spectroscopic determination of force constants.

Simandiras, E.D.; Handy, N.C.; Amos, R.D.

1988-04-07

249

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

250

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

2008-10-21

251

Aeroelastic Computations of a Compressor Stage Using the Harmonic Balance Method  

NASA Technical Reports Server (NTRS)

The aeroelastic characteristics of a compressor stage were analyzed using a computational fluid dynamic (CFD) solver that uses the harmonic balance method to solve the governing equations. The three dimensional solver models the unsteady flow field due to blade vibration using the Reynolds-Averaged Navier-Stokes equations. The formulation enables the study of the effect of blade row interaction through the inclusion of coupling modes between blade rows. It also enables the study of nonlinear effects of high amplitude blade vibration by the inclusion of higher harmonics of the fundamental blade vibration frequency. In the present work, the solver is applied to study in detail the aeroelastic characteristics of a transonic compressor stage. Various parameters were included in the study: number of coupling modes, blade row axial spacing, and operating speeds. Only the first vibration mode is considered with amplitude of oscillation in the linear range. Both aeroelastic stability (flutter) of rotor blade and unsteady loading on the stator are calculated. The study showed that for the stage considered, the rotor aerodynamic damping is not influenced by the presence of the stator even when the axial spacing is reduced by nearly 25 percent. However, the study showed that blade row interaction effects become important for the unsteady loading on the stator when the axial spacing is reduced by the same amount.

Reddy, T. S. R.

2010-01-01

252

Vibration manual  

NASA Technical Reports Server (NTRS)

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

Green, C.

1971-01-01

253

A First Principles Density-Functional Calculation of the Electronic and Vibrational Structure of the Key Melanin Monomers  

E-print Network

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

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

2004-01-23

254

Chiral vibrations in the A=135 region  

E-print Network

Chiral vibrations are studied with the RPA plus self-consistent tilted axis cranking formalism in the A=135 region. In this method chiral vibrations appear as a precursor to the static chiral regime. The properties of the RPA phonons are discussed and compared to experimental data. We discuss the limits the chiral region and the transition to the non harmonic regime.

Daniel Almehed; Friedrich Doenau; Stefan Frauendorf

2007-09-06

255

Vibrational Thermodynamics of Materials Brent Fultz  

E-print Network

Vibrational Thermodynamics of Materials Brent Fultz California Institute of Technology, W. M. Keck Laboratory, Pasadena CA 91125 USA July 6, 2009 Abstract. The literature on vibrational thermodynamics of harmonic phonons in alloys are organized into thermodynamic models for unmixing and ordering

Fultz, Brent

256

The designated harmonic suppression for SPWM  

NASA Astrophysics Data System (ADS)

SPWM is a critical method used in asynchronous motor-driven area. But harmonic components of inverter output wave impair its application in motor speed control. A new mixed algorithm was proposed for SPWM, which was a designated harmonic suppression technology by way of improved regular sampling in low voltage and low frequency and harmonic elimination in high voltage and high frequency. This algorithm was based on both analysis of sampled SPWM and Fourier series transform method and aimed at eliminating some odd harmonic components to obtain an identical sine wave. After explication of the harmonic elimination procedure and real time calculation process, an effective control mode and its control circuit were put forward so that the designated harmonic suppression made a reality. Applied it in whole speed adjusting range, the voltage can be conveniently controlled and high frequency harmonic components of SPWM are also improved.

Ping, Yang; Yang, Shi-ping

2005-12-01

257

Structural and vibrational studies and molecular force field of zinc difluoromethanesulfinate  

NASA Astrophysics Data System (ADS)

The new compound zinc difluoromethanesulfinate salt, Zn(SO2CF2H)2 (recently synthesized by Fujiwara et al. [12]) was characterized by infrared and Raman spectroscopies. The ab initio calculations were used to study the structures and vibrational properties of the compound and its SO2CF2H- anion. Employing the HF and B3LYP levels of theory, the molecular structures of both species were theoretically determined in gas phase and the harmonic vibrational frequencies were evaluated at the same levels. Also, the structure of a monohydrated complex in accordance with the observed experimental structure was optimized. The calculated harmonic vibrational frequencies for zinc difluoromethanesulfinate are consistent with the experimental IR and Raman spectra. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by difluoromethanesulfinate groups of this compound as monodentate and bidentate ligands. A complete assignment of all the observed bands in the IR and Raman spectra for zinc difluoromethanesulfinate was performed. The nature of the CF, SO and Zn ? O bonds and the topological properties of the compound were investigated and analyzed by means of Natural Bond Order (NBO) and Bader's Atoms in Molecules theory (AIM), respectively.

Romano, Elida; Davies, Lilian Emilia; Brandán, Silvia Antonia

2013-07-01

258

Analysis of a high Tc superconducting levitation system with vibration isolation control  

SciTech Connect

This paper presents a method for controlling vibrations of a levitated high Tc superconducting body subjected to base disturbances. To have the control forces, an actuator consisting of a permanent magnet with an electromagnet was presented. The analytical solution for calculating levitation forces due to the permanent magnet and the control currents in the electromagnet was obtained. The levitation forces obtained coincide with the previously published results. The equation of motion of the levitated body subjected to base disturbances under the control was presented. Nonlinear vibrations of the body were first discussed; then the method of vibration isolation control using the direct disturbance cancellation combining the velocity feedback control was investigated. Numerical calculations were carried out for the levitation forces, with respect to the levitated body subjected to harmonic or pulse base excitations. It was clarified that the present method is valid for controlling nonlinear systems like the magnetic levitated superconducting body.

Nagaya, Kosuke [Gunma Univ., Kiryu, Gunma (Japan). Dept. of Mechanical Engineering] [Gunma Univ., Kiryu, Gunma (Japan). Dept. of Mechanical Engineering

1996-03-01

259

Raman and infrared spectra, conformational stability, barriers to internal rotation, vibrational assignment, and ab initio calculations of 3-methyl-3-butenenitrile  

NASA Astrophysics Data System (ADS)

The Raman (3500-30 cm -1) spectra of liquid and solid and the infrared (3500-40 cm -1) spectra of gaseous and solid 3-methyl-3-butenenitrile, CH 2dbnd6 C(CH 3)CH 2C tbnd6 N, have been recorded. Both cis and gauche conformers have been identified in the fluid phases but only the cis form remains in the solid. Variable temperature (-55 to -100 °C) studies of the infrared spectra of the sample dissolved in liquid xenon have been carried out. From these data, the enthalpy difference has been determined to be 163±16 cm -1 (1.20±0.19 kJ mol -1), with the cis conformer the more stable rotamer. It is estimated that there is 48±2% of the gauche conformer present at 25°C. A complete vibrational assignment is proposed for the cis conformer based on infrared band contours, relative intensities, depolarization ratios and group frequencies. Several of the fundamentals for the gauche conformer have also been identified. The vibrational assignments are supported by normal coordinate calculations utilizing ab initio force constants. Complete equilibrium geometries have been obtained for both rotamers by ab initio calculations employing the 6-31G(d), 6-311G(d,p), 6-311+G(d,p) and 6-311+G(2d,2p) basis sets at the levels of restricted Hartree-Fock (HF) and/or Møller-Plesset perturbation theory to the second order (MP2). Only with the 6-311G(2d,2p) and 6-311G(2df,2pd) basis sets with or without diffuse functions is the cis conformer predicted to be more stable than the gauche form. The potential energy terms for the conformational interchange have been obtained at the MP2(full)/6-311+G(2d,2p) level, and compared to those obtained from the experimental data. The results are discussed and compared to the corresponding quantities obtained for some similar molecules.

Durig, James R.; Zheng, Chao; Guirgis, Gamil A.; Zhen, Huimin; Drew, Andrea S.; Durig, Douglas T.

2006-03-01

260

Vibration modes of giant gravitons  

Microsoft Academic Search

We examine the spectrum of small vibrations of giant gravitons when the gravitons expand in anti--de Sitter space and when they expand on the sphere. For any given angular harmonic, the modes are found to have frequencies related to the curvature length scale of the background; these frequencies are independent of radius (and hence angular momentum) of the brane itself.

Sumit R. Das; Antal Jevicki; Samir D. Mathur

2001-01-01

261

The Effect of Anharmonicity on Diatomic Vibration; A Spreadsheet Simulation  

NSDL National Science Digital Library

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

262

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

263

Molecular geometry, vibrational spectra, atomic charges, frontier molecular orbital and Fukui function analysis of antiviral drug zidovudine  

NASA Astrophysics Data System (ADS)

The solid phase FT-IR and FT-Raman spectra of zidovudine (AZT) were recorded in the regions 4000-400 and 3500-100 cm-1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of zidovudine were obtained by the Restricted Hartree-Fock (RHF) density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. The harmonic vibrational frequencies for zidovudine were calculated and the scaled values have been compared with experimental values of FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The harmonic vibrational wave numbers and intensities of vibrational bands of zidovudine with its cation and anion were calculated and compared with the neutral AZT. The DFT calculated HOMO and LUMO energies shows that charge transfer occurs within the molecule. The electron density-based local reactivity descriptors such as Fukui functions were calculated to explain the chemical selectivity or reactivity site in AZT.

Ramkumaar, G. R.; Srinivasan, S.; Bhoopathy, T. J.; Gunasekaran, S.

2012-12-01

264

Molecular geometry, vibrational spectra, atomic charges, frontier molecular orbital and Fukui function analysis of antiviral drug zidovudine.  

PubMed

The solid phase FT-IR and FT-Raman spectra of zidovudine (AZT) were recorded in the regions 4000-400 and 3500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of zidovudine were obtained by the Restricted Hartree-Fock (RHF) density functional theory (DFT) with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. The harmonic vibrational frequencies for zidovudine were calculated and the scaled values have been compared with experimental values of FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The harmonic vibrational wave numbers and intensities of vibrational bands of zidovudine with its cation and anion were calculated and compared with the neutral AZT. The DFT calculated HOMO and LUMO energies shows that charge transfer occurs within the molecule. The electron density-based local reactivity descriptors such as Fukui functions were calculated to explain the chemical selectivity or reactivity site in AZT. PMID:23064549

Ramkumaar, G R; Srinivasan, S; Bhoopathy, T J; Gunasekaran, S

2012-12-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

266

Equilibrium structure and large amplitude motion investigation of 1,4-disilacyclohexa-2,5-diene by means of electron diffraction, vibrational spectroscopic data, and ab initio calculations  

NASA Astrophysics Data System (ADS)

Equilibrium and thermal average structure of 1,4-disilacyclohexa-2,5-diene (DSCHD) was determined by applying procedures that have been recently developed for joint treatment of gas phase electron diffraction and molecular spectroscopy data guided by ab initio calculations. Both large amplitude motion and anharmonic vibrational effects were taken into account. Similar structural results were obtained by considering DSCHD molecule as a unique equilibrium conformer and as a set of quasi-conformers describing large amplitude motion. The determined equilibrium structural parameters for DSCHD (planar configuration) are: r e( Si- C)=1.861(2) Å, r e( C?C)=1.346(3) Å, r e( Si- H)=1.498(10) Å, r e( C- H)=1.074(10) Å, ?(C-Si-C)=109.9(3)°, ?(H-C?C)=116.7(10)°, and ?(H-Si-H)=107.9(10)°. Uncertainties given in parentheses include three times standard deviation and a systematic error.

Dakkouri, M.; Kochikov, I. V.; Tarasov, Yu. I.; Vogt, N.; Vogt, J.; Bitschenauer, R.

2002-04-01

267

a Computational Study of the Vibrational - Stretching and - Bending Spectrum of the Water Trimer  

NASA Astrophysics Data System (ADS)

We have studied the vibrational O--H stretching and H--O--H angle bending spectrum of the water trimer computationally around the cyclic minimum energy structure. We obtain the energies and intensities of the fundamental and overtone transitions. Earlier we have modeled the water trimer as three individually vibrating monomer units. In this work we have improved our previous model by including the potential energy coupling between the three hydrogen bonded O--H stretching modes. An internal coordinate Hamiltonian is constructed for each water unit using a kinetic energy operator, which is exact within the Born-Oppenheimer approximation for a triatomic molecule. The potential energy coupling terms between the hydrogen bonded O--H stretching modes are added in the model. The O--H distances and the H--O--H bending angles are used as the vibrational coordinates. The potential energy grid is calculated using the coupled cluster method with single, double and perturbative triple excitations (CCSD(T)) with correlation consistent aug-cc-pVTZ basis set around the optimized geometry. The potential energy surface (PES) is obtained by fitting an analytical function to the potential energy grid. The dipole moment surface is calculated using the finite differences method. The vibrational problem has been solved with the variational method with a harmonic oscillator basis for all the vibrational coordinates. We calculate the transition intensities using the wavefunctions obtained from the variational calculation.

Salmi, Teemu; Halonen, Lauri

2011-06-01

268

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

269

Sunspots and Their Simple Harmonic Motion  

ERIC Educational Resources Information Center

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.

2013-01-01

270

Structure and vibrational analysis of methyl 3-amino-2-butenoate  

NASA Astrophysics Data System (ADS)

The molecular structure and vibrational spectra of methyl 3-(amino)-2-butenoate (MAB) and its deuterated analogous, D3MAB, were investigated using density functional theory (DFT) calculations. The geometrical parameters and harmonic vibrational wavenumbers of MAB and D3MAB were obtained at the B3LYP/6-311++G(d,p) level. The calculated vibrational wavenumbers were compared with the corresponding experimental results. The assignment of the IR and Raman spectra of MAB and D3MAB was facilitated by calculating the anharmonic wavenumbers at the B3LYP/6-311G(d,p) level as well as recording and calculating the MAB spectra in CCl4 solution. The assigned normal modes were compared with a similar molecule, 4-amino-3-penten-2-one (APO). The theoretical results were in good agreement with the experimental data. All theoretical and experimental results indicate that substitution of a methyl group with a methoxy group considerably weakens the intramolecular hydrogen bond and reduces the ?-electron delocalization in the chelated ring system. The IR spectra also indicate that in the solid state, MAB is not only engaged in an intramolecular hydrogen bond, but also forms an intermolecular hydrogen bond. However, the intermolecular hydrogen bond will be removed in dilute CCl4 solution.

Berenji, Ali Reza; Tayyari, Sayyed Faramarz; Rahimizadeh, Mohammad; Eshghi, Hossein; Vakili, Mohammad; Shiri, Ali

2013-02-01

271

Analysis of imaging properties of a vibrating thin flat mirror.  

PubMed

Thin flat mirrors are often used in designing various optical measurement systems. Such mirrors are generally deformed by environmental conditions during measurements. A detailed theory of deformation of a thin flat mirror that oscillates harmonically in the direction of the normal to its surface is introduced in our work. The mirror is treated as a vibrating membrane, and the time-dependent effect of the mirror deformation on the properties of reflected light is studied. A relation is derived for a dynamic wave aberration. On the basis of this relation, calculation of the Strehl definition of the deformed mirror is performed both by exact integration and by approximation. The results obtained can be used for analysis of the influence of mechanical vibrations on the accuracy of optical measurement systems in various practical applications where thin flat mirrors are used. PMID:15384439

Miks, Antonin; Novak, Jiri

2004-09-01

272

Non-equilibrium Casimir force between vibrating plates.  

PubMed

We study the fluctuation-induced, time-dependent force between two plates confining a correlated fluid which is driven out of equilibrium mechanically by harmonic vibrations of one of the plates. For a purely relaxational dynamics of the fluid we calculate the fluctuation-induced force generated by the vibrating plate on the plate at rest. The time-dependence of this force is characterized by a positive lag time with respect to the driving. We obtain two distinctive contributions to the force, one generated by diffusion of stress in the fluid and another related to resonant dissipation in the cavity. The relation to the dynamic Casimir effect of the electromagnetic field and possible experiments to measure the time-dependent Casimir force are discussed. PMID:23326401

Hanke, Andreas

2013-01-01

273

Non-Equilibrium Casimir Force between Vibrating Plates  

PubMed Central

We study the fluctuation-induced, time-dependent force between two plates confining a correlated fluid which is driven out of equilibrium mechanically by harmonic vibrations of one of the plates. For a purely relaxational dynamics of the fluid we calculate the fluctuation-induced force generated by the vibrating plate on the plate at rest. The time-dependence of this force is characterized by a positive lag time with respect to the driving. We obtain two distinctive contributions to the force, one generated by diffusion of stress in the fluid and another related to resonant dissipation in the cavity. The relation to the dynamic Casimir effect of the electromagnetic field and possible experiments to measure the time-dependent Casimir force are discussed. PMID:23326401

Hanke, Andreas

2013-01-01

274

Experimental and theoretical debate on efficient second harmonic generation in Bis (Cinnamic acid): Hexamine cocrystal  

NASA Astrophysics Data System (ADS)

Second harmonic generation (SHG) in Bis (Cinnamic acid): Hexamine cocrystal was extensively analyzed through charge transfer (CT). The CT interactions through hydrogen bonding were well established with the aid of vibrational analysis and Natural Bond Orbital (NBO) analysis. The retentivity of coplanar nature of the cinnamic acid in the cocrystal was confirmed through UV-Visible spectroscopy and supported by Raman studies. Structural analysis indicated the quinoidal character of the given material presenting a high SHG efficiency. The first order hyperpolarizability value was calculated theoretically by density functional theory (DFT) and Hartree-Fock (HF) methods in support for the large value of SHG.

Vijayalakshmi, S.; Kalyanaraman, S.; Ravindran, T. R.

2014-02-01

275

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

276

Molecular structure, vibrational spectroscopy, NBO and HOMO, LUMO studies of o-methoxybenzonitrile.  

PubMed

In the present study, the FT-IR and FT-Raman spectra of o-methoxybenzonitrile (O-MBN) have been recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The fundamental modes of vibrational frequencies of O-MBN are assigned. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of ab initio Hartree-Fock (HF) and density functional theory (DFT) gradient calculations with complete relaxation in the potential energy surface using 6-311++G(d,p) basis set. The vibrational frequencies which were determined experimentally from the spectral data are compared with those obtained theoretically from ab initio and DFT calculations. A close agreement was achieved between the observed and calculated frequencies by refinement of the scale factors. The infrared and Raman spectra were also predicted from the calculated intensities. Thermodynamic properties like entropy, heat capacity, zero point energy, have been calculated for the molecule. The predicted first hyperpolarizability also shows that the molecule might have a reasonably good non-linear optical (NLO) behavior. The calculated HOMO-LUMO energy gap reveals that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions, charge delocalization have been analyzed using natural bond orbitals (NBO) analysis. Unambiguous vibrational assignment of all the fundamentals was made using the total energy distribution (TED). PMID:25058575

Elanthiraiyan, M; Jayasudha, B; Arivazhagan, M

2015-01-01

277

Coupled rotor/fuselage dynamic analysis of the AH-1G helicopter and correlation with flight vibrations data  

NASA Technical Reports Server (NTRS)

Under a research program designated Design Analysis Methods for VIBrationS (DAMVIBS), existing analytical methods are used for calculating coupled rotor-fuselage vibrations of the AH-1G helicopter for correlation with flight test data from an AH-1G Operational Load Survey (OLS) test program. The analytical representation of the fuselage structure is based on a NASTRAN finite element model (FEM), which has been developed, extensively documented, and correlated with ground vibration test. One procedure that was used for predicting coupled rotor-fuselage vibrations using the advanced Rotorcraft Flight Simulation Program C81 and NASTRAN is summarized. Detailed descriptions of the analytical formulation of rotor dynamics equations, fuselage dynamic equations, coupling between the rotor and fuselage, and solutions to the total system of equations in C81 are included. Analytical predictions of hub shears for main rotor harmonics 2p, 4p, and 6p generated by C81 are used in conjunction with 2p OLS measured control loads and a 2p lateral tail rotor gearbox force, representing downwash impingement on the vertical fin, to excite the NASTRAN model. NASTRAN is then used to correlate with measured OLS flight test vibrations. Blade load comparisons predicted by C81 showed good agreement. In general, the fuselage vibration correlations show good agreement between anslysis and test in vibration response through 15 to 20 Hz.

Corrigan, J. C.; Cronkhite, J. D.; Dompka, R. V.; Perry, K. S.; Rogers, J. P.; Sadler, S. G.

1989-01-01

278

Window functions for the calculation of the time domain averages of the vibration of the individual planet gears and sun gear in an epicyclic gearbox  

NASA Astrophysics Data System (ADS)

An existing technique which enables the estimation of the time domain averages of the tooth meshing vibration of the individual planet and sun gears in an epicyclic gearbox from measured vibration signals has been revised. A key feature of the existing technique is the sampling of the vibration signal within a rectangular window in the time domain when one of the planet gears is close to the vibration transducer. The revised technique permits the use of other window functions, and a detailed analysis shows that the errors in the estimate of the time domain average can be expressed in terms of the window function. Several suitable window functions which enable a reduction in the level of the errors are demonstrated by numerical examples and by the analysis of data from a test on a helicopter gearbox with deliberate damage to one of the planet gears.

McFadden, P. D.

1994-04-01

279

Molecular structure, vibrational spectra and HOMO, LUMO analysis of yohimbine hydrochloride by density functional theory and ab initio Hartree–Fock calculations  

Microsoft Academic Search

Yohimbine hydrochloride (YHCl) is an aphrodisiac and promoted for erectile dysfunction, weight loss and depression. The optimized geometry, total energy, potential energy surface and vibrational wavenumbers of yohimbine hydrochloride have been determined using ab initio, Hartree–Fock (HF) and density functional theory (DFT\\/B3LYP) method with 6-311++G(d,p) basis set. A complete vibrational assignment is provided for the observed Raman and IR spectra

Bhawani Datt Joshi; Anubha Srivastava; Poonam Tandon; Sudha Jain

2011-01-01

280

Active vibration control in Duffing mechanical systems using dynamic vibration absorbers  

NASA Astrophysics Data System (ADS)

This paper deals with the multi-frequency harmonic vibration suppression problem in forced Duffing mechanical systems using passive and active linear mass-spring-damper dynamic vibration absorbers. An active vibration absorption scheme is proposed to extend the vibrating energy dissipation capability of a passive dynamic vibration absorber for multiple excitation frequencies and, simultaneously, to perform reference position trajectory tracking tasks planned for the nonlinear primary system. A differential flatness-based disturbance estimation scheme is also described to estimate the unknown multiple time-varying frequency disturbance signal affecting the differentially flat nonlinear vibrating mechanical system dynamics. Some numerical simulation results are provided to show the efficient performance of the proposed active vibration absorption scheme and the fast estimation of the vibration disturbance signal.

Beltrán-Carbajal, F.; Silva-Navarro, G.

2014-07-01

281

Analysis of potential helicopter vibration reduction concepts  

NASA Technical Reports Server (NTRS)

Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location.

Landgrebe, A. J.; Davis, M. W.

1985-01-01

282

Vibrational spectroscopic (FT-IR, FT-Raman, SERS) and quantum chemical calculations of 3-(10,10-dimethyl-anthracen-9-ylidene)-N,N,N-trimethylpropanaminiium chloride (Melitracenium chloride).  

PubMed

FT-IR, FT-Raman spectra of Melitracenium chloride were recorded and analyzed. SERS spectrum was recorded in silver colloid. The vibrational wavenumbers were computed using DFT quantum chemical calculations. The data obtained from wavenumber calculations are used to assign vibrational bands obtained in infrared and Raman spectra as well as in SERS of the studied molecule. Potential energy distribution was done using GAR2PED program. The geometrical parameters (SDD) of the title compound are in agreement with the XRD results. The presence anthracene ring modes in the SERS spectrum suggest a tilted orientation with respect to the metal surface. The methyl groups in the title molecule are also close to the metal surface. The first hyperpolarizability, NBO analysis and molecular electrostatic potential results are also reported. PMID:24200651

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

2014-01-01

283

Theoretical study of anharmonicity in the vibrational spectrum of the perfluorocyclopropenyl cation  

NASA Astrophysics Data System (ADS)

Complete theoretical calculations for the structure, anharmonic force field up to partial sixth order, and anharmonic vibrational frequencies of C3F+3 have been carried out. The procedure included ab initio calculation of the vibrational potential-energy surface at the 6-311G plus double polarization plus local MP4(SDQ) level, followed by a complete, 12-mode variational solution of the vibrational Schrödinger equation using a configuration-interaction (CI) expansion from a large, well-selected harmonic oscillator basis. The geometric parameters of C3F+3 (D3h) were optimized as 1.3796 Å for the CC bond lengths and 1.2615 Å for the CF distances. Localized orbitals show strong ?-bond character for the CF linkages, conjugated with the ring ? orbital. The fundamental vibrational frequencies of C3F+3 are 1999.5, 742.8 (a'1); 767.3 (a2); 1596.9, 998.9, 271.3 (e'); 250.0 (a`2); and 664.1 (e`). These frequencies agree with condensed phase measurements of Raman and infrared spectra with a ±11.5 cm-1 average deviation, the largest difference appearing for the CF bending and wagging frequencies. The first vibrational overtone frequencies of C3F+3 are also predicted. This completely ab initio calculation of anharmonic frequencies also leads to detailed bond characterization and full information on all intermode interactions.

Xie, Yaoming; Boggs, James E.

1989-07-01

284

Spectroscopic analysis and DFT calculations of a food additive Carmoisine  

NASA Astrophysics Data System (ADS)

FT-IR and Raman techniques were employed for the vibrational characterization of the food additive Carmoisine (E122). The equilibrium geometry, various bonding features, and harmonic vibrational wavenumbers have been investigated with the help of density functional theory (DFT) calculations. A good correlation was found between the computed and experimental wavenumbers. Azo stretching wavenumbers have been lowered due to conjugation and ?-electron delocalization. Predicted electronic absorption spectra from TD-DFT calculation have been analysed comparing with the UV-vis spectrum. The first hyperpolarizability of the molecule is calculated. Intramolecular charge transfer (ICT) responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and C-H⋯O, improper, blue shifted hydrogen bonds have been analysed using natural bond orbital (NBO) analysis.

Snehalatha, M.; Ravikumar, C.; Hubert Joe, I.; Sekar, N.; Jayakumar, V. S.

2009-04-01

285

The harmonic oscillator and nuclear physics  

NASA Technical Reports Server (NTRS)

The three-dimensional harmonic oscillator plays a central role in nuclear physics. It provides the underlying structure of the independent-particle shell model and gives rise to the dynamical group structures on which models of nuclear collective motion are based. It is shown that the three-dimensional harmonic oscillator features a rich variety of coherent states, including vibrations of the monopole, dipole, and quadrupole types, and rotations of the rigid flow, vortex flow, and irrotational flow types. Nuclear collective states exhibit all of these flows. It is also shown that the coherent state representations, which have their origins in applications to the dynamical groups of the simple harmonic oscillator, can be extended to vector coherent state representations with a much wider range of applicability. As a result, coherent state theory and vector coherent state theory become powerful tools in the application of algebraic methods in physics.

Rowe, D. J.

1993-01-01

286

Vibrational spectroscopic study and NBO analysis on tranexamic acid using DFT method  

NASA Astrophysics Data System (ADS)

In this work, we reported the vibrational spectra of tranexamic acid (TA) by experimental and quantum chemical calculation. The solid phase FT-Raman and FT-IR spectra of the title compound were recorded in the region 4000 cm-1 to 100 cm-1 and 4000 cm-1 to 400 cm-1 respectively. The molecular geometry, harmonic vibrational frequencies and bonding features of TA in the ground state have been calculated by using density functional theory (DFT) B3LYP method with standard 6-31G(d,p) basis set. The scaled theoretical wavenumber showed very good agreement with the experimental values. The vibrational assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes. Stability of the molecule, arising from hyperconjugative interactions and charge delocalization, has been analyzed using Natural Bond Orbital (NBO) analysis. The results show that ED in the ?* and ?* antibonding orbitals and second order delocalization energies E(2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The electrostatic potential mapped onto an isodensity surface has been obtained. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the title compound at different temperatures were calculated in gas phase.

Muthu, S.; Prabhakaran, A.

2014-08-01

287

Vibrational spectroscopic studies and Natural Bond Orbital analysis of 4,6-dichloro-2-(methylthio)pyrimidine based on density functional theory  

Microsoft Academic Search

The FT-IR and FT-Raman spectra of 4,6-dichloro-2-(methylthio)pyrimidine (DMP) have been recorded and analyzed. The optimized geometry, intramolecular hydrogen bonding, and harmonic vibrational wave numbers of DMP have been investigated with the help of B3LYP density functional theory (DFT) method supplemented with 6-31G** basis set. The infrared and Raman spectra were predicted theoretically from the calculated intensities. Natural Bond Orbital (NBO)

V. Balachandran; A. Lakshmi; A. Janaki

2011-01-01

288

Coupling between plate vibration and acoustic radiation  

NASA Technical Reports Server (NTRS)

A detailed numerical investigation of the coupling between the vibration of a flexible plate and the acoustic radiation is performed. The nonlinear Euler equations are used to describe the acoustic fluid while the nonlinear plate equation is used to describe the plate vibration. Linear, nonlinear, and quasi-periodic or chaotic vibrations and the resultant acoustic radiation are analyzed. We find that for the linear plate response, acoustic coupling is negligible. However, for the nonlinear and chaotic responses, acoustic coupling has a significant effect on the vibration level as the loading increases. The radiated pressure from a plate undergoing nonlinear or chaotic vibrations is found to propagate nonlinearly into the far-field. However, the nonlinearity due to wave propagation is much weaker than that due to the plate vibrations. As the acoustic wave propagates into the far-field, the relative difference in level between the fundamental and its harmonics and subharmonics decreases with distance.

Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

1992-01-01

289

Vibrational contributions to the stability of point defects in bcc iron: A first-principles study  

NASA Astrophysics Data System (ADS)

The purpose of this study is to investigate the modes of vibration of the self-interstitial atoms and the vacancy in bcc iron and to estimate how the vibrational properties can affect the stability of these defects. The phonon density of states of the vacancy and the self-interstitials have been calculated within the quasi harmonic approximation using density functional theory calculations. It was observed that self-interstitial atoms have several localized high frequency modes of vibration related to the stretching of the dumbbell bond, but also soft modes favoring their migration. From the phonon density of states, the vibrational contributions to the free energy have been estimated for finite temperatures. Results are compared to previous work performed by others using empirical potentials. We found a rather large formation entropy for the vacancy, SVf=4.08kB. Our results show that the vibrational entropy can have a significant influence on the formation of the point defects even at moderate temperature. Possible consequences on the mobility of these defects are also discussed.

Lucas, G.; Schäublin, R.

2009-09-01

290

Vibrations and Wave Tutorial Models  

NSDL National Science Digital Library

The Vibrations and Wave Tutorial Models demonstrate how the superposition principle gives rise to wave phenomena, such as standing waves and beats. The five models cataloged in this item demonstrate: simple harmonic motion, history graphs, standing waves, standing waves on an infinite string, and beats. You can modify these simulations if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item.

Wheaton, Spencer

2014-08-11

291

Good Vibrations  

NSDL National Science Digital Library

This lesson (on pages 15-24 of PDF) explores how sound is caused by vibrating objects. It explains that we hear by feeling vibrations passing through the air. Learners take part in several demonstrations, making those vibrations visible. They put a tuning fork in a shallow pan of water and use it to bounce a ping-pong ball, showing the fact that the tuning fork is vibrating when it's making a sound. There are extensions described involving comb kazoos, rubber band guitars, and putting rice or cereal on top of a drum.

Omsi

2010-01-01

292

Molecular vibrational states during a collision  

NASA Technical Reports Server (NTRS)

Alternative algebraic techniques to approximate a given Hamiltonian by a harmonic oscillator are described both for time-independent and time-dependent systems. We apply them to the description of a one dimensional atom-diatom collision. From the resulting evolution operator, we evaluate vibrational transition probabilities as well as other time-dependent properties. As expected, the ground vibrational state becomes a squeezed state during the collision.

Recamier, Jose A.; Jauregui, Rocio

1995-01-01

293

Monitoring molecular dynamics using coherent electrons from high harmonic generation  

PubMed Central

We report a previously undescribed spectroscopic probe that makes use of electrons rescattered during the process of high-order harmonic generation. We excite coherent vibrations in SF6 using impulsive stimulated Raman scattering with a short laser pulse. A second, more intense laser pulse generates high-order harmonics of the fundamental laser, at wavelengths of ?20–50 nm. The high-order harmonic yield is observed to oscillate, at frequencies corresponding to all of the Raman-active modes of SF6, with an asymmetric mode most visible. The data also show evidence of relaxation dynamics after impulsive excitation of the molecule. Theoretical modeling indicates that the high harmonic yield should be modulated by both Raman and infrared-active vibrational modes. Our results indicate that high harmonic generation is a very sensitive probe of vibrational dynamics and may yield more information simultaneously than conventional ultrafast spectroscopic techniques. Because the de Broglie wavelength of the recolliding electron is on the order of interatomic distances, i.e., ?1.5 Å, small changes in the shape of the molecule lead to large changes in the high harmonic yield. This work therefore demonstrates a previously undescribed spectroscopic technique for probing ultrafast internal dynamics in molecules and, in particular, on the chemically important ground-state potential surface. PMID:16895984

Wagner, Nicholas L.; Wuest, Andrea; Christov, Ivan P.; Popmintchev, Tenio; Zhou, Xibin; Murnane, Margaret M.; Kapteyn, Henry C.

2006-01-01

294

Vibrational C-H overtone spectroscopy and bond distances of butenes dissolved in liquid Xe  

NASA Astrophysics Data System (ADS)

Vibrational overtone spectra of isobutene, cis-2-butene, and trans-2-butene dissolved in liquid xenon at 163 K, have been recorded between 5000 and 16500 cm -1. Spectral regions for the first four overtones were measured using a Fourier transform spectrophotometer. The fifth overtone (? ? = 6) spectra were recorded with a double beam (pump-probe) thermal lens technique. Band deconvolution allowed isolation of individual transitions. Local-mode parameters were calculated for C-H oscillators in solution and compared with gas phase local-mode parameters. Density functional theory calculations were done to obtain C-H bond lengths and vibrational frequencies for the three butene isomers. Frequency shifts (? ?) with respect to gas phase results are attributed to changes in harmonic frequency and anharmonicity of the particular C-H bond of the sample dissolved in the inert liquid solvent.

Lopez-Calvo, Alfredo; Diez-y-Riega, Helena; Manzanares, Carlos E.

2009-10-01

295

Experimental and DFT studies on the vibrational, electronic spectra and NBO analysis of thiamethoxam  

NASA Astrophysics Data System (ADS)

Vibrational and electronic spectral measurements were performed for 3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro) amine (thiamethoxam). Optimized geometrical structure and harmonic vibrational frequencies were calculated with ab initio RHF and DFT (B3LYP, CAMB3LYP, M06 and PBE1PBE) methods with 6-311++G (d, p) basis set. Complete assignments of the observed spectra were proposed. The absorption spectra of the compound were computed in gas-phase using TD-B3LYP/6-311++G (d, p) approach and H2O solution using PCM-TD-B3LYP/6-311++G (d, p) approach. The calculated results matched well with the experimental values. Temperature dependence of thermodynamic parameters in the range of 100-1000 K were determined. The bond orbital occupancies, contribution from parent natural bond orbital (NBO), the natural atomic hybrids was discussed.

Zhang, Fang; Zhang, Yu; Ni, Haiwei; Ma, Kuirong; Li, Rongqing

2014-01-01

296

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

297

Improved continuous-time higher harmonic control using [Eta] [infinity] methods  

E-print Network

The helicopter is a versatile aircraft that can take-off and land vertically, hover efficiently, and maneuver in confined space. This versatility is enabled by the main rotor, which also causes undesired harmonic vibration ...

Fan, Frank H. (Frank Hsiao)

2013-01-01

298

Harmonic power flow for unbalanced systems  

SciTech Connect

In this paper a harmonic power flow that analyzes harmonics in unbalanced systems is presented. The developed algorithm has two steps which are executed successively: the first is a fundamental frequency power flow for the ac linear network in which non-linear loads are represented by current sources. The second is a frequency-domain iterative Newton-Raphson method to calculate the harmonics generated by non-linear loads. In this second step, the ac linear network is represented by a generalized Thevenin equivalent with respect to the non-linear loads, obtained from the power flow solution. Both linear and non-linear loads are considered in terms of power.

Valcarcel, M.; Mayordomo, J.G. (Univ. Politecnica de Madrid (Spain). Dept. de Ingenieria Electrica)

1993-10-01

299

Good Vibrations  

NSDL National Science Digital Library

In this activity, learners experiment with their voices and noisemakers to understand the connections between vibrations and the sounds created by those vibrations. This resource includes three quick demonstration activities that can be used independently or as a group to introduce learners to the basic elements of sound.

Omsi

2004-01-01

300

Vibrational Coupling  

SciTech Connect

By homing in on the distribution patterns of electrons around an atom, a team of scientists team with Berkeley Lab's Molecular Foundry showed how certain vibrations from benzene thiol cause electrical charge to "slosh" onto a gold surface (left), while others do not (right). The vibrations that cause this "sloshing" behavior yield a stronger SERS signal.

None

2011-01-01

301

Model for Vibrational Relaxation of Diatomic Gases behind Shock Waves  

Microsoft Academic Search

The problem of the vibrational relaxation of a system of harmonic oscillators is examined for the case in which the oscillators are in contact with a heat bath whose total heat capacity is finite and whose temperature therefore varies during the relaxation process. An analysis is carried out for processes in which the initial distribution of vibrational energy is a

Robert Herman; Robert J. Rubin

1959-01-01

302

Conformational properties of F 2S dbnd N sbnd CF 2sbnd N dbnd SF 2 and F 2S dbnd N sbnd CF 2sbnd N dbnd S(O)F 2: Vibrational spectra and quantum chemical calculations  

NASA Astrophysics Data System (ADS)

The structural and conformational properties of F 2S dbnd N sbnd CF 2sbnd N dbnd SF 2 and F 2S dbnd N sbnd CF 2sbnd N dbnd S(O)F 2 were studied by vibrational spectroscopy (IR(gas) and Raman(liquid)) and by quantum chemical calculations, using B3LYP and MP2 methods with small and large basis sets. Since the SF 2 and S(O)F 2 groups can adopt syn (s) or anti (a) position ( syn/ anti of the F sbnd S sbnd F bisector with respect to the adjacent N sbnd C bond) and the orientation around the two N sbnd C bonds can be trans (t) or gauche (g), a large number of possible conformers is expected. In the case of F 2S dbnd N sbnd CF 2sbnd N dbnd SF 2 calculations with large basis sets predict the presence of a single conformer with both SF 2 groups in syn position and gauche orientation around both N sbnd C bonds (s-g-g-s conformer). This is confirmed by the vibrational spectra. For F 2S dbnd N sbnd CF 2sbnd N dbnd S(O)F 2 analysis of the vibrational spectra in combination with the quantum chemical calculations suggests the predominance of the s-g-t-s conformer, i.e. syn position of SF 2 and S(O)F 2 groups, gauche orientation around one N sbnd C bond and trans orientation around the other N sbnd C bond, and the presence of a smaller amounts of the s-t-g-s and s-g-g-s conformers.

Antognini, Andrea Flores; Robles, Norma L.; Cutin, Edgardo H.; Oberhammer, Heinz

2011-09-01

303

Enhancing tidal harmonic analysis: Robust (hybrid L1 ) solutions  

E-print Network

Enhancing tidal harmonic analysis: Robust (hybrid L1 =L2 ) solutions Keith E. Leffler Ã?, David A 24 February 2008 Accepted 28 April 2008 Keywords: Tides Tidal analysis Harmonic analysis Robust is calculated from the power spectrum of the residual, a calculation that filters broad spectrum noise

Jay, David

304

Anharmonic midinfrared vibrational spectra of benzoic acid monomer and dimer  

NASA Astrophysics Data System (ADS)

Anharmonic vibrational calculations for the benzoic acid monomer and dimer in the mid-IR regime (500-1800cm-1) are reported. Harmonic frequencies and intensities are obtained at the DFT/B3LYP level of theory employing D95(d,p) and cc-pVTZ basis sets. Anharmonic corrections obtained from standard perturbation theory lead to redshifts of 1%-3%. In almost all cases, the resulting frequencies deviate by less than 1% from previous measurements [Bakker et al., J. Chem. Phys. 119, 11180 (2003)]. Calculated intensities are in qualitative agreement with the absorption experiment, with the cc-pVTZ values being superior to the D95(d,p) ones for a few modes of the dimer. The antisymmetric out-of-plane bending mode of the dimer, which is strongly blueshifted with respect to the monomer frequency, represents a remarkable exception: The harmonic frequencies obtained for the two basis sets differ notably from each other, and the anharmonically corrected frequencies deviate from the experimental value by 8% [D95(d,p)] or 3% (cc-pVTZ). Nonperturbative calculations in reduced dimensionality reveal that the relatively small total anharmonic shift (few tens of cm-1) comprises of partly much larger contributions (few hundreds of cm-1) which are mostly canceling each other. Many of the individual anharmonic couplings are beyond the validity of second-order perturbation theory based on cubic and semidiagonal quartic force constants only. This emphasizes the need for high-dimensional, nonperturbative anharmonic calculations at high quantum-chemical level when accurate frequencies of H-atom vibrations in double hydrogen bonds are sought for.

Antony, Jens; von Helden, Gert; Meijer, Gerard; Schmidt, Burkhard

2005-07-01

305

Vibrational frequencies, structural confirmation stability and HOMO-LUMO analysis of nicotinic acid ethyl ester with experimental (FT-IR and FT-Raman) techniques and quantum mechanical calculations  

NASA Astrophysics Data System (ADS)

The FT-IR and FT-Raman spectra of nicotinic acid ethyl ester (abbreviated as NAEE, C8H9NO2) have been recorded in the region 3600-10 cm-1. Potential energy curve was computed by means of scanning CCCdbnd O torsion angle. The optimized geometric parameters geometry optimization and the energies associated possible two conformers (C1 and C2) were computed. The computational results diagnose the most stable conformer of NAEE as the C1 form. The optimum molecular geometries, energies, normal mode wavenumbers, infrared and Raman intensities, corresponding vibrational assignments, atomic charges, HOMO-LUMO analysis and thermo-dynamical parameters were investigated with the help of HF, B3LYP and LSDA methods with 6-311G(d,p) and 6-311G++(d,p) basis sets. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanics (SQM) method. Thermodynamic properties of the title compound at different temperatures were calculated. The results of the calculations were applied to simulate infrared and Raman spectra of the title compound which show excellent agreement with the observed spectra.

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

2012-06-01

306

Vertical vibration and shape oscillation of acoustically levitated water drops  

NASA Astrophysics Data System (ADS)

We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

Geng, D. L.; Xie, W. J.; Yan, N.; Wei, B.

2014-09-01

307

Vibrational spectroscopic investigations and computational study of 5-tert-butyl-N-(4-trifluoromethylphenyl)pyrazine-2-carboxamide.  

PubMed

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. PMID:23727674

Joseph, Tomy; Varghese, Hema Tresa; Yohannan Panicker, C; Viswanathan, K; Dolezal, Martin; Manojkumar, T K; Van Alsenoy, Christian

2013-09-01

308

NIS, IR and Raman spectra with quantum mechanical calculations for analyzing the force field of hypericin model compounds  

SciTech Connect

Geometry optimization as well as harmonic force field calculations at HF and DFT levels of theory have been performed in order to elucidate the ground state properties of anthrone and emodin, two polycyclic conjugated molecules considered as hypericin model compounds. NIS, IR and FT-Raman spectra of these compounds have been recorded to validate the calculated results (geometry and vibrational modes). Calculated NIS spectra using the lowest energy conformers are in agreement with experiment. In addition, the intramolecular H-bonds in emodin predicted by the calculations can be evidenced using IR spectra as a function of temperature.

Ulicny, Jozef [Laboratoire de Physicochimie Biomoleculaire et Cellulaire, UPRESA 7033, Universite P. and M. Curie, Case Courrier 138, 75252 Paris Cedex 05 (France); Department of Biophysics, Safarik University, Jesenna 5, 04154 Kosice (Slovakia); Leulliot, Nicolas; Ghomi, Mahmoud [Laboratoire de Physicochimie Biomoleculaire et Cellulaire, UPRESA 7033, Universite P. and M. Curie, Case Courrier 138, 75252 Paris Cedex 05 (France); Grajcar, Lydie; Baron, Marie-Helene [Laboratoire de Dynamique, Interactions et Reactivite, CNRS, 2 rue H. Dunant, 94320 Thiais (France); Jobic, Herve [Institut de Recherche sur la Catalyse, 2 avenue A. Einstein, 69626 Villeurbanne (France)

1999-06-15

309

Anharmonic vibrator description of collective nuclei  

SciTech Connect

It is shown that a simple anharmonic vibrator model can account for the properties of yrast states in collective nuclei, as well as the quasi-band states built on the {gamma}-vibration or on the O{sub 2}{sup +} state. This description extends from nearly harmonic vibrator nuclei to pure rotor nuclei and encompasses both energies and B(E2) values. It survives both ``horizontal`` and ``vertical`` perspectives on the data of nuclear physics and offers a challenge to microscopic theories of nuclear structure.

Casten, R.F. [Brookhaven National Lab., Upton, NY (United States); Zamfir, N.V. [Brookhaven National Lab., Upton, NY (United States)]|[Clark Univ., Worcester, MA (United States)]|[Institute of Atomic Physics, Bucharest (Romania)

1995-07-01

310

Single Phase Harmonic Limits  

Microsoft Academic Search

The International Electrotechnical Commission (IEC) sets limits for harmonics in the current of small single-phase or three-phase loads, less than 16 A per phase, in Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (IEC 61000-3-2). The IEEE Single Phase Harmonics Task Force (P1495) is developing a similar standard for single phase loads of less than

Ward Jewell; Daniel J. Ward; Principal Engineer; Dominion Virginia Power

2002-01-01

311

Workshop on Harmonic Oscillators  

NASA Technical Reports Server (NTRS)

Proceedings of a workshop on Harmonic Oscillators held at the College Park Campus of the University of Maryland on March 25 - 28, 1992 are presented. The harmonic oscillator formalism is playing an important role in many branches of physics. This is the simplest mathematical device which can connect the basic principle of physics with what is observed in the real world. The harmonic oscillator is the bridge between pure and applied physics.

Han, D. (editor); Kim, Y. S. (editor); Zachary, W. W. (editor)

1993-01-01

312

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

313

Anomalies in high-order harmonic generation at relativistic intensities  

SciTech Connect

High-order harmonic generation from a solid target surface has been investigated using femtosecond laser pulses focused to intensities greater than 10{sup 18} W/cm{sup 2}. The experiments show that the harmonics are very intense, with a conversion efficiency that is one or two orders of magnitude larger than that of harmonics generated in gases. Beside the observation of presently the shortest wavelength harmonics from femtosecond-laser solid target interaction, i.e., down to 22 nm, an anomaly has been observed in the harmonic spectrum. In contrast to the expected well-known continuous 'roll off' of the high-harmonic orders, the harmonic intensity decreases with the increase of harmonic order, but in between shows minima which are significantly less intense than the neighboring harmonics. Furthermore, the order of the harmonic minima depend on target material. Additional calculations using numerical kinetic particle simulations and a simpler oscillating mirror model show that the physical origin of these modulations is an intricate interplay of resonance absorption and ponderomotive force which leads to a complex electron density profile evolution. Furthermore, this is emphasized by a spectral line analysis of the harmonics. In agreement with the theory, broad lines have been observed and, in particular for the harmonics in the minima, a complex interference structure is present.

Teubner, U.; Foerster, E. [Abteilung Roentgenoptik, Institut fuer Optik und Quantenelektronik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Pretzler, G.; Eidmann, K.; Witte, K. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Schlegel, Th. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt (Germany)

2003-01-01

314

Vibrating wire field-measuring technique  

Microsoft Academic Search

The technique described here is dedicated to the problem of alignment of quadrupole magnets, a very important issue for particle accelerators. The technique is based on the excitation of the harmonics of a wire vibration by Lorenz forces between current in a wire and the surrounding magnetic field. Theoretical analyses show that knowing the amplitude and the phase of the

Alexander Temnykh

1997-01-01

315

Stability analysis of rotating blade bending vibration due to torsional excitation  

Microsoft Academic Search

This paper studies the forced vibrations of a flexible rotating blade under the excitation of shaft torsional vibration. A reduced order nonlinear dynamic model is adopted, wherein the torsional vibration degree of freedom is substituted by a simple harmonic motion with a frequency that is function of the system rotating speed. The resulting system of second-order ordinary differential equation with

B. O. Al-Bedoor; A. A. Al-Qaisia

2005-01-01

316

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

317

FT-IR, FT-Raman, NMR spectra, density functional computations of the vibrational assignments (for monomer and dimer) and molecular geometry of anticancer drug 7-amino-2-methylchromone  

NASA Astrophysics Data System (ADS)

Vibrational assignments for the 7-amino-2-methylchromone (abbreviated as 7A2MC) molecule using a combination of experimental vibrational spectroscopic measurements and ab initio computational methods are reported. The optimized geometry, intermolecular hydrogen bonding, first order hyperpolarizability and harmonic vibrational wavenumbers of 7A2MC have been investigated with the help of B3LYP density functional theory method. The calculated molecular geometry parameters, the theoretically computed vibrational frequencies for monomer and dimer and relative peak intensities were compared with experimental data. DFT calculations using the B3LYP method and 6-31 + G(d,p) basis set were found to yield results that are very comparable to experimental IR and Raman spectra. Detailed vibrational assignments were performed with DFT calculations and the potential energy distribution (PED) obtained from the Vibrational Energy Distribution Analysis (VEDA) program. Natural Bond Orbital (NBO) study revealed the characteristics of the electronic delocalization of the molecular structure. 13C and 1H NMR spectra have been recorded and 13C and 1H nuclear magnetic resonance chemical shifts of the molecule have been calculated using the gauge independent atomic orbital (GIAO) method. Furthermore, All the possible calculated values are analyzed using correlation coefficients linear fitting equation and are shown strong correlation with the experimental data.

Mariappan, G.; Sundaraganesan, N.

2014-04-01

318

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 as…

Wadhwa, Ajay

2009-01-01

319

The study of damped harmonic oscillations using an electronic counter  

Microsoft Academic Search

We study damped harmonic oscillations in mechanical systems like the loaded spring and simple pendulum with the help of an oscillation measuring electronic counter. The experimental data are used in a software program that solves the differential equation for damped vibrations of any system and determines its position, velocity and acceleration as a function of time. The method developed in

Ajay Wadhwa

2009-01-01

320

Covariant harmonic oscillators and coupled harmonic oscillators  

NASA Technical Reports Server (NTRS)

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 high-energy laboratories. It is shown also that the coupled oscillator system has the SL(4,r) symmetry in classical mechanics, while the present formulation of quantum mechanics can accommodate only the Sp(4,r) portion of the SL(4,r) symmetry. The possible role of the SL(4,r) symmetry in quantum mechanics is discussed.

Han, Daesoo; Kim, Young S.; Noz, Marilyn E.

1995-01-01

321

Vibration generators  

SciTech Connect

Apparatus for generating vibrations in a medium, such as the ground, comprises a first member which contacts the medium, means , preferably electromagnetic, which includes two relatively movable members for generating vibrations in the apparatus and means operatively connecting the said two members to said first member such that the relatively amplitudes of the movements of said three members can be adjusted to match the impedances of the apparatus and the medium.

Lerwill, W.E.

1980-09-16

322

Vibration-induced interfacial instabilities in viscoelastic fluids.  

PubMed

Vertically vibrated interfaces between viscoelastic fluids may arise in contexts as diverse as ultrasonic emulsification, microgravity materials processing, and geophysics. If the vibration amplitude is large enough at a given frequency, the interface can become unstable and give rise to standing waves. The present work provides a linear analysis of this phenomenon for the cases where either or both of the fluids are viscoelastic. The fluids are assumed to be laterally unbound, and Floquet theory is used to develop a recursion relation between the temporal modes of the interfacial deformation. Conversion of this relation into a matrix eigenvalue problem allows determination of the critical vibration amplitude needed to excite the standing waves and the corresponding critical wave number. Using a single-mode Maxwell model to describe the viscoelasticity and considering infinite fluid depths, we present calculations for three cases: bottom fluid viscoelastic/top fluid Newtonian, bottom fluid Newtonian/top fluid viscoelastic, and both fluids viscoelastic. When only one of the fluids is viscoelastic, the interfacial waves can respond harmonically to the forcing. The waves may also be excited more easily than in the case where both fluids are Newtonian. When both of the fluids are viscoelastic, it appears possible to excite Stoneley-like waves at the interface. PMID:11863651

Kumar, Satish

2002-02-01

323

Molecular structure and vibrational and chemical shift assignments of 3-(2-hydroxyphenyl)-4-phenyl-1H-1,2,4-triazole-5-(4H)-thione by DFT and ab initio HF calculations.  

PubMed

The molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO) 1H and 13C chemical shift values and several thermodynamic parameters of 3-(2-Hydroxyphenyl)-4-phenyl-1H-1,2,4-triazole-5-(4H)-thione in the ground state have been calculated by using the Hartree-Fock (HF) and density functional methods (BLYP and B3LYP) with 6-31G(d) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The molecule contains one O-H...N and one C-H...pi (phenyl) intramolecular interactions. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Data of the title compound display significant structure-correlation and provide the basis for future design of efficient materials having the derivatives of 1,2,4-triazole. Also, calculated 1H chemical shift values compared with the experimental ones. PMID:19264542

Avci, Davut; Atalay, Yusuf; Sekerci, Mehmet; Dinçer, Muharrem

2009-07-01

324

Vibration sensors  

NASA Astrophysics Data System (ADS)

Today, vibration sensors with low and medium sensitivities are in great demand. Their applications include robotics, navigation, machine vibration monitoring, isolation of precision equipment & activation of safety systems e.g. airbags in automobiles. Vibration sensors have been developed at SSPL, using silicon micromachining to sense vibrations in a system in the 30 - 200 Hz frequency band. The sensing element in the silicon vibration sensor is a seismic mass suspended by thin silicon hinges mounted on a metallized glass plate forming a parallel plate capacitor. The movement of the seismic mass along the vertical axis is monitored to sense vibrations. This is obtained by measuring the change in capacitance. The movable plate of the parallel plate capacitor is formed by a block connected to a surrounding frame by four cantilever beams located on sides or corners of the seismic mass. This element is fabricated by silicon micromachining. Several sensors in the chip sizes 1.6 cm x 1.6 cm, 1 cm x 1 cm and 0.7 cm x 0.7 cm have been fabricated. Work done on these sensors, techniques used in processing and silicon to glass bonding are presented in the paper. Performance evaluation of these sensors is also discussed.

Gupta, Amita; Singh, Ranvir; Ahmad, Amir; Kumar, Mahesh

2003-10-01

325

Vibrational and thermodynamic properties of ?-, ?-, ?-, and 6, 6, 12-graphyne structures.  

PubMed

Electronic, vibrational, and thermodynamic properties of different graphyne structures, namely ?-, ?-, ?-, and 6, 6, 12-graphyne, are investigated through first principles-based quasi-harmonic approximation by using phonon dispersions predicted from density-functional perturbation theory. Similar to graphene, graphyne was shown to exhibit a structure with extraordinary electronic features, mechanical hardness, thermal resistance, and very high conductivity from different calculation methods. Hence, characterizing its phonon dispersions and vibrational and thermodynamic properties in a systematic way is of great importance for both understanding its fundamental molecular properties and also figuring out its phase stability issues at different temperatures. Thus, in this research work, thermodynamic stability of different graphyne allotropes is assessed by investigating vibrational properties, lattice thermal expansion coefficients, and Gibbs free energy. According to our results, although the imaginary vibrational frequencies exist for ?-graphyne, there is no such a negative behavior for ?-, ?-, and 6, 6, 12-graphyne structures. In general, the Grüneisen parameters and linear thermal expansion coefficients of these structures are calculated to be rather more negative when compared to those of the graphene structure. In addition, the predicted difference between the binding energies per atom for the structures of graphene and graphyne points out that graphyne networks have relatively lower phase stability in comparison with the graphene structures. PMID:24737253

Perkgöz, Nihan Kosku; Sevik, Cem

2014-05-01

326

Structural, vibrational and thermodynamic properties of Mg2 FeH6 complex hydride  

NASA Astrophysics Data System (ADS)

Mg2FeH6, which has one of the highest hydrogen storage capacities among Mg based 3d-transitional metal hydrides, is considered as an attractive material for hydrogen storage. Within density-functional perturbation theory (DFPT), we have investigated the structural, vibrational and thermodynamic properties of Mg2FeH6. The band structure calculation shows that this compound is a semiconductor with a direct X-X energy gap of 1.96 eV. The calculated phonon frequencies for the Raman-active and the infrared-active modes are assigned. The phonon dispersion curves together with the corresponding phonon density of states and longitudinal-transverse optical (LO-TO) splitting are also calculated. Findings are also presented for the temperature-dependent behaviors of some thermodynamic properties such as free energy, internal energy, entropy and heat capacity within the quasi-harmonic approximation based on the calculated phonon density of states.

Zhou, H. L.; Yu, Y.; Zhang, H. F.; Gao, T.

2011-02-01

327

Molecular structure, vibrational spectroscopic (FT-IR, FT-Raman), UV–vis spectra, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis, thermodynamic properties of benzophenone 2,4-dicarboxylic acid by ab initio HF and density functional method  

Microsoft Academic Search

The FT-IR (4000–450cm?1) and FT-Raman spectra (3500–100cm?1) of benzophenone 2,4-dicarboxylic acid (2,4-BDA) have been recorded in the condensed state. Density functional theory calculation with B3LYP\\/6-31G(d,p) basis set have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman activities and bonding features of the title compounds. The assignments of the vibrational

K. Chaitanya

328

Density Functional Theory Study on Molecular Structure and Vibrational Spectra of 4-AMINO-1-METHYLBENZENE  

NASA Astrophysics Data System (ADS)

We have discussed the applicability limits of HF, MP2 and DFT-B3LYP methods on 4-amino-1-methylbenzene in our previous work [1]. We have found the DFT-B3LYP method very promising for vibrational spectral analyses. In this study, we extend DFT calculations with different basis sets for more appropriateness to exprimental results. The optimized molecular structures, vibrational frequencies and coresponding vibrational assigments of 4-amino-1-methylbenzene have been obtained from the DFT-B3LYP, DFT-B3PW91 and DFT-PBEPBE methods implementing the 6-311G+** and aug-ccPVQZ basis sets. Scale factors, which bring computational frequencies in closer agreement with the experimental data, have been calculated for predominant vibrational motions of the normal modes at each level considered. All observed harmonic IR and Raman bands of 4-amino-1-methylbenzene have been assigned in the frameworks of the calculations. The comparison of calculations with FT-IR and FT-Raman spectra of 4-amino-1-methylbenzene have been carried out. We are planing to extend this work to the transition metal complexes in the form of MX2L2 [M: Transition metals e.g. Mn(II), Co(II) and Ni(II) . . . ; X : Halogens e.g Cl, Br, I, L: 4-amino-1-methylbenzene] 1. A. Altun, K. Golcuk, M. Kumru, "Structure and vibrational spectra of p-methylaniline: Hartree-Fock, MP2 and density functional theory studies", JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 637: 155-169 OCT 3 2003

Kumru, M.; Bardakci, T.; Sari, L.

2009-06-01

329

Theoretical interpretation of the vibrational spectrum of bicyclo[1.1.0]butane in terms of an ab initio anharmonic model  

NASA Astrophysics Data System (ADS)

The anharmonic vibrational IR and Raman spectra of the bicyclo[1.1.0]butane molecule have been calculated in the range of up to 4000 cm-1 using a numerical and analytical realization of the van Vleck second-order operator perturbation theory. Cubic and quartic force constants in normal coordinates, as well as cubic surfaces of the dipole moment and polarizability, have been found by numerical differentiation of the corresponding first and second derivatives calculated by the MP2/cc-pVTZ quantum-mechanical method. In order to increase the prediction accuracy of vibrational transitions, corresponding harmonic frequencies have been obtained by the CCSD(T)/cc-pVTZ high-precision quantum mechanical method. The anharmonic intensities of the IR and Raman spectra have been calculated using canonical transformations of the operators of the dipole moment and polarizability expanded into a Taylor series around the equilibrium configuration. The assignment of experimental vibrational bands in the IR and Raman spectra has been analyzed. It has been shown that the anharmonic calculation based on the above-described procedure of combining more exact harmonic frequencies with the anharmonic force field obtained with a more economical method makes possible the reliable interpretation of the majority of spectral bands, including Fermi and Darling-Dennison resonances.

Berezin, K. V.; Nechaev, V. V.; Berezin, M. K.; Stepanov, N. F.; Krasnoshchekov, S. V.

2014-09-01

330

The ground electronic state of 1,2-dichloroethane I. Ab initio investigation of the geometrical, vibrational and torsional structure  

NASA Astrophysics Data System (ADS)

The trans and gauche isomers of 1,2-dichloroethane are characterized using ab initio calculations at the MP4(SDQ) level of theory with the full double zeta polarized D95** basis set. The molecular geometry parameters, the torsion potential and the harmonic frequency of the normal modes of vibrations are calculated. The integrated intensity and the rotational type of the infrared fundamental bands also are determined. New labelling of the normal modes of vibration is introduced for the gauche isomer. The relative abundance and stability of both isomers are discussed. The torsional motion is investigated by means of an effective model taking the geometrical relaxation into account and leading to a theoretical torsional spectrum.

El Youssoufi, Y.; Herman, M.; Lievin, J.

331

Dynamics of the [4Fe-4S] Cluster in Pyrococcus furiosus D14C Ferredoxin via Nuclear Resonance Vibrational and Resonance Raman Spectroscopies, Force Field Simulations, and Density Functional Theory Calculations  

PubMed Central

We have used 57Fe nuclear resonance vibrational spectroscopy (NRVS) to study oxidized and reduced forms of the [4Fe-4S] cluster in the D14C variant ferredoxin from Pyrococcus furiosus (Pf D14C Fd). To assist the normal mode assignments, we recorded the NRVS of D14C ferredoxin samples with 36S substituted into the [4Fe-4S] cluster bridging sulfide positions, and a model compound without ligand side chains: (Ph4P)2[Fe4S4Cl4]. Several distinct regions of NRVS intensity are identified, ranging from `protein' and torsional modes below 100 cm?1, through bending and breathing modes near 150 cm?1, to strong bands from Fe-S stretching modes between 250 cm?1 and ~400 cm?1. The oxidized ferredoxin samples were also investigated by resonance Raman (RR) spectroscopy. We found good agreement between NRVS and RR frequencies, but because of different selection rules, the intensities vary dramatically between the two types of spectra. The 57Fe partial vibrational densities of states (PVDOS) for the oxidized samples were interpreted by normal mode analysis with optimization of Urey-Bradley force fields for local models of the [4Fe-4S] clusters. Full protein model calculations were also conducted using a supplemented CHARMM force field, and these calculations revealed low frequency modes that may be relevant to electron transfer with Pf Fd partners. Density functional theory (DFT) calculations complemented these empirical analyses, and DFT was used to estimate the reorganization energy associated with the [Fe4S4]2+/1+ redox cycle. Overall, the NRVS technique demonstrates great promise for the observation and quantitative interpretation of the dynamical properties of Fe-S proteins. PMID:21500788

Mitra, Devrani; Pelmenschikov, Vladimir; Guo, Yisong; Case, David A.; Wang, Hongxin; Dong, Weibing; Tan, Ming-Liang; Ichiye, Toshiko; Jenney, Francis E.; Adams, Michael W. W.; Yoda, Yoshitaka; Zhao, Jiyong; Cramer, Stephen P.

2011-01-01

332

Illustration: The Harmonic Oscillator  

NASA Astrophysics Data System (ADS)

To illustrate the formalism on a simple prototype problem, one may look at the harmonic oscillator. In the spirit of this picture, in fact, one can eschew solving the Schrödinger problem and plugging the wavefunctions into (4)...

Curtright, Thomas L.; Fairlie, David B.; Zachos, Cosmas K.

2014-11-01

333

Simple Harmonic Motion  

NSDL National Science Digital Library

This simulation offers two examples of simple harmonic motion, a mass on a spring and a simple pendulum. The applet allows you to adjust variables and observe the effects these changes have on the movement of the systems.

Pfaff, Raman

2008-07-15

334

Simple Harmonic Motion  

NSDL National Science Digital Library

This site from HyperPhysics presents an introduction to simple harmonic motion. It is explained using a concept map that features equations and diagrams. Links to other concepts involved are also included.

Nave, C. R.; University, Department O.

335

Vibration characteristics of OH-58A helicopter main rotor transmission  

NASA Technical Reports Server (NTRS)

Experimental vibration tests covering a range of torque and speed conditions were performed on the OH-58A helicopter main rotor transmission at the NASA Lewis Research Center. Signals from accelerometers located on the transmission housing were analyzed by using Fourier spectra, power spectral density functions, and averaging techniques. Most peaks of the Fourier spectra occurred at the spiral bevel and planetary gear mesh harmonics. The highest level of vibration occurred at the spiral bevel meshing frequency. Transmission speed and vibration measurement location had a significant effect on measured vibration; transmission torque and measurement direction had a small effect.

Lewicki, David G.; Coy, John J.

1987-01-01

336

Conformational stability, vibrational and NMR analysis, chemical potential and thermodynamical parameter of 3-tert-butyl-4-hydroxyanisole.  

PubMed

The FT-IR and FT-Raman spectra of 3-tert-butyl-4-hydroxyanisole (TBHA) molecule have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. Optimized geometrical structure, harmonic vibrational frequencies has been computed by B3LYP level using 6-31G (d,p) and 6-311+G (d,p) basis sets. The observed FT-IR and FT-Raman vibrational frequencies are analyzed and compared with theoretically predicted vibrational frequencies. The geometries and normal modes of vibration obtained from DFT method are in good agreement with the experimental data. The Mulliken charges, the natural bonding orbital (NBO) analysis, the first-order hyperpolarizability of the investigated molecule were computed using DFT calculations. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and analyzed. The isotropic chemical shift computed by (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the TBHA calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations. PMID:25173520

Balachandran, V; Karpagam, V; Revathi, B; Kavimani, M; Santhi, G

2015-01-25

337

Studies on molecular structure, vibrational spectra and molecular docking analysis of 3-Methyl-1,4-dioxo-1,4-dihydronaphthalen-2-yl 4-aminobenzoate.  

PubMed

The molecular structure, vibrational analysis and molecular docking analysis of the 3-Methyl-1,4-dioxo-1,4-dihydronaphthalen-2-yl 4-aminobenzoate (MDDNAB) molecule have been carried out using FT-IR and FT-Raman spectroscopic techniques and DFT method. The equilibrium geometry, harmonic vibrational wave numbers, various bonding features have been computed using density functional method. The calculated molecular geometry has been compared with experimental data. The detailed interpretation of the vibrational spectra has been carried out by using VEDA program. The hyper-conjugative interactions and charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The simulated FT-IR and FT-Raman spectra satisfactorily coincide with the experimental spectra. The PES and charge analysis have been made. The molecular docking was done to identify the binding energy and the Hydrogen bonding with the cancer protein molecule. PMID:24813290

Suresh, D M; Amalanathan, M; Joe, I Hubert; Jothy, V Bena; Diao, Yun-Peng

2014-09-15

338

Improved Estimation Of Vibrations In Engines And Pumps  

NASA Technical Reports Server (NTRS)

Method of estimating vibrational loads upon, and vibrational power dissipated in, rocket engines, pumps, turbomachines, and similar flow-through-type machinery derived from older vibration-scaling concept of estimating vibrations of components of rocket engine in design stage, without complicated mathematical modeling and calculations. Methods involve scaling vibrations via global variables like mass-flow rates and exit velocities of engine exhausts. Present method called "Improved Composite Loads Spectra-Component Scaling Criteria".

Chow, David C.

1996-01-01

339

Low complexity feature extraction for classification of harmonic signals  

NASA Astrophysics Data System (ADS)

In this dissertation, feature extraction algorithms have been developed for extraction of characteristic features from harmonic signals. The common theme for all developed algorithms is the simplicity in generating a significant set of features directly from the time domain harmonic signal. The features are a time domain representation of the composite, yet sparse, harmonic signature in the spectral domain. The algorithms are adequate for low-power unattended sensors which perform sensing, feature extraction, and classification in a standalone scenario. The first algorithm generates the characteristic features using only the duration between successive zero-crossing intervals. The second algorithm estimates the harmonics' amplitudes of the harmonic structure employing a simplified least squares method without the need to estimate the true harmonic parameters of the source signal. The third algorithm, resulting from a collaborative effort with Daniel White at the DSP Lab, University of Nebraska-Lincoln, presents an analog front end approach that utilizes a multichannel analog projection and integration to extract the sparse spectral features from the analog time domain signal. Classification is performed using a multilayer feedforward neural network. Evaluation of the proposed feature extraction algorithms for classification through the processing of several acoustic and vibration data sets (including military vehicles and rotating electric machines) with comparison to spectral features shows that, for harmonic signals, time domain features are simpler to extract and provide equivalent or improved reliability over the spectral features in both the detection probabilities and false alarm rate.

William, Peter E.

340

Theory of vibrationally assisted tunneling for hydroxyl monomer flipping on Cu(110)  

NASA Astrophysics Data System (ADS)

To describe vibrationally mediated configuration changes of adsorbates on surfaces we have developed a theory to calculate both reaction rates and pathways. The method uses the T-matrix to describe excitations of vibrational states by the electrons of the substrate, adsorbate, and tunneling electrons from a scanning tunneling probe. In addition to reaction rates, the theory also provides the reaction pathways by going beyond the harmonic approximation and using the full potential energy surface of the adsorbate which contains local minima corresponding to the adsorbates different configurations. To describe the theory, we reproduce the experimental results in [T. Kumagai et al., Phys. Rev. B 79, 035423 (2009), 10.1103/PhysRevB.79.035423], where the hydrogen/deuterium atom of an adsorbed hydroxyl (OH/OD) exhibits back and forth flipping between two equivalent configurations on a Cu(110) surface at T =6 K. We estimate the potential energy surface and the reaction barrier, ˜160 meV, from DFT calculations. The calculated flipping processes arise from (i) at low bias, tunneling of the hydrogen through the barrier, (ii) intermediate bias, tunneling electrons excite the vibrations increasing the reaction rate although over the barrier processes are rare, and (iii) higher bias, overtone excitations increase the reaction rate further.

Gustafsson, Alexander; Ueba, Hiromu; Paulsson, Magnus

2014-10-01

341

Excited-state geometries and vibrational frequencies studied using the analytical energy gradients of the direct symmetry-adapted cluster-configuration interaction method. I. HAX-type molecules.  

PubMed

In this series of studies, we systematically apply the analytical energy gradients of the direct symmetry-adapted cluster-configuration interaction singles and doubles nonvariational method to calculate the equilibrium geometries and vibrational frequencies of excited and ionized states of molecules. The harmonic vibrational frequencies were calculated using the second derivatives numerically computed from the analytical first derivatives and the anharmonicity was evaluated from the three-dimensional potential energy surfaces around the local minima. In this paper, the method is applied to the low-lying valence singlet and triplet excited states of HAX-type molecules, HCF, HCCl, HSiF, HSiCl, HNO, HPO, and their deuterium isotopomers. The vibrational level emission spectra of HSiF and DSiF and absorption spectra of HSiCl and DSiCl were also simulated within the Franck-Condon approximation and agree well with the experimental spectra. The results show that the present method is useful and reliable for calculating these quantities and spectra. The change in geometry in the excited states was qualitatively interpreted in the light of the electrostatic force theory. The effect of perturbation selection with the localized molecular orbitals on the geometrical parameters and harmonic vibrational frequencies is also discussed. PMID:21806128

Ehara, Masahiro; Oyagi, Fumito; Abe, Yoko; Fukuda, Ryoichi; Nakatsuji, Hiroshi

2011-07-28

342

Algebraic methods in vibrational spectroscopy  

SciTech Connect

These lectures review some advances in the algebraic description of molecules from two point of views: structure and dynamics. We start by presenting the basic ideas involved in the traditional description of molecular structure in configuration space, where the Born-Oppenheimer and rotor-rigid approximations are assumed to be valid. We then focus on the vibrational degrees of freedom in order to introduce the traditional algebraic realization in terms of bosonic operators of harmonic oscillators. This analysis allows the algebraic methods based on dynamical unitary groups to be introduced as a anharmonization procedure where the local bosonic operators are translated into operators satisfying the su(2) commutation relations. Some examples of the vibrational spec-troscopic description are presented. Concerned with the dynamical point of view an algebraic model to describe collinear collisions in the semiclassical approximation is presented.

Lemus, Renato [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico, DF (Mexico)

2011-03-21

343

Nonlinear Vibrations of Ferroelectric Bimorph Cantilever  

NASA Astrophysics Data System (ADS)

Nonlinear vibrations of a bimorph LiNbO3 microcantilever are investigated. A periodically poled LiNbO3 wafer is used as an initial chip. The cantilever is micro-machined near an interdomain wall between two inversely poled domains. The vibrations are excited by an applied rf-voltage, and motion of a cantilever tip is detected optically. Nonlinearity is revealed by measuring the changes in the dependencies of vibration amplitude versus frequency when amplitude increases, and by reading of sub-harmonic oscillations. A surface of the microcantilever may be modified with a silane, which is sensitive to certain biomolecules. This composite nonlinear micro-vibrator may be used for developing a smart biosensor operating in ambient atmosphere in a real time mode.

Ostrovskii, Igor; Nadtochiy, Andriy

2008-06-01

344

Vibrational study, first hyperpolarizability and HOMO-LUMO analyses on the structure of 2-hydroxy-6-nitro toluene  

NASA Astrophysics Data System (ADS)

Vibrational spectral measurements, namely, FT-infrared (4000-400 cm-1) and FT-Raman (3500-50 cm-1) spectra have been made for 2-hydroxy-6-nitrotoluene (HNT) and assigned to different normal modes of the molecule. Quantum chemical calculations of energies, geometrical structure, harmonic vibrational frequencies intensities and vibrational wavenumbers of HNT were carried out by ab initio HF and density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set. The differences between the observed and scaled wave number values of most of the fundamentals are very small. The values of the total dipole moment (?) and first hyperpolarizability (?) of the investigated molecule were computed by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p) basis set quantum mechanical calculations. The calculated results also show that the HNT molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. A detailed interpretation of the infrared and Raman spectra of HNT is also reported based on total energy distribution (TED). The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The results of the calculations were applied to simulated infrared and Raman spectra of the title compound which showed excellent agreement with the observed spectra.

Arivazhagan, M.; Thilagavathi, G.

2012-06-01

345

Understanding Vibration Spectra of Planetary Gear Systems for Fault Detection  

NASA Technical Reports Server (NTRS)

An understanding of the vibration spectra is very useful for any gear fault detection scheme based upon vibration measurements. The vibration measured from planetary gears is complicated. Sternfeld noted the presence of sidebands about the gear mesh harmonics spaced at the planet passage frequency in spectra measured near the ring gear of a CH-47 helicopter. McFadden proposes a simple model of the vibration transmission that predicts high spectral amplitudes at multiples of the planet passage frequency, for planetary gears with evenly spaced planets. This model correctly predicts no strong signal at the meshing frequency when the number of teeth on the ring gear is not an integer multiple of the number of planets. This paper will describe a model for planetary gear vibration spectra developed from the ideas started in reference. This model predicts vibration to occur only at frequencies that are multiples of the planet repetition passage frequency and clustered around gear mesh harmonics. Vibration measurements will be shown from tri-axial accelerometers mounted on three different planetary gear systems and compared with the model. The model correctly predicts the frequencies with large components around the first several gear mesh harmonics in measurements for systems with uniformly and nonuniformly spaced planet gears. Measurements do not confirm some of the more detailed features predicted by the model. Discrepancies of the ideal model to the measurements are believed due to simplifications in the model and will be discussed. Fault detection will be discussed applying the understanding will be discussed.

Mosher, Marianne

2003-01-01

346

Quantum chemical approach for condensed-phase thermochemistry: Proposal of a harmonic solvation model.  

PubMed

We propose a novel quantum chemical method, called the harmonic solvation model (HSM), for calculating thermochemical parameters in the condensed phase, particularly in the liquid phase. The HSM represents translational and rotational motions of a solute as vibrations interacting with a cavity wall of solvent molecules. As examples, the HSM and the ideal-gas model (IGM) were used for the standard formation reaction of liquid water, combustion reactions of liquid formic acid, methanol, and ethanol, vapor-liquid equilibration of water and ethanol, and dissolution of gaseous CO2 in water. The numerical results confirmed the reliability and applicability of the HSM. In particular, the temperature dependence of the Gibbs energy of liquid molecules was accurately reproduced by the HSM; for example, the boiling point of water was reasonably determined using the HSM, whereas the conventional IGM treatment failed to obtain a crossing of the two Gibbs energy curves for gaseous and liquid water. PMID:25381501

Nakai, Hiromi; Ishikawa, Atsushi

2014-11-01

347

Quantum chemical approach for condensed-phase thermochemistry: Proposal of a harmonic solvation model  

NASA Astrophysics Data System (ADS)

We propose a novel quantum chemical method, called the harmonic solvation model (HSM), for calculating thermochemical parameters in the condensed phase, particularly in the liquid phase. The HSM represents translational and rotational motions of a solute as vibrations interacting with a cavity wall of solvent molecules. As examples, the HSM and the ideal-gas model (IGM) were used for the standard formation reaction of liquid water, combustion reactions of liquid formic acid, methanol, and ethanol, vapor-liquid equilibration of water and ethanol, and dissolution of gaseous CO2 in water. The numerical results confirmed the reliability and applicability of the HSM. In particular, the temperature dependence of the Gibbs energy of liquid molecules was accurately reproduced by the HSM; for example, the boiling point of water was reasonably determined using the HSM, whereas the conventional IGM treatment failed to obtain a crossing of the two Gibbs energy curves for gaseous and liquid water.

Nakai, Hiromi; Ishikawa, Atsushi

2014-11-01

348

Experimental and computational study on molecular structure and vibrational analysis of an antihyperglycemic biomolecule: gliclazide.  

PubMed

In present study, the experimental and theoretical harmonic vibrational frequencies of gliclazide molecule have been investigated. The experimental FT-IR (400-4000 cm(-1)) and Laser-Raman spectra (100-4000 cm(-1)) of the molecule in the solid phase were recorded. Theoretical vibrational frequencies and geometric parameters (bond lengths and bond angles) have been calculated using ab initio Hartree Fock (HF), density functional theory (B3LYP hybrid function) methods with 6-311++G(d,p) and 6-31G(d,p) basis sets by Gaussian 09W program. The assignments of the vibrational frequencies were performed by potential energy distribution (PED) analysis by using VEDA 4 program. Theoretical optimized geometric parameters and vibrational frequencies have been compared with the corresponding experimental data, and they have been shown to be in a good agreement with each other. Also, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies have been found. PMID:25062059

Karakaya, Mustafa; Kürekçi, Mehmet; Eskiyurt, Buse; Sert, Yusuf; Ç?rak, Ça?r?

2015-01-25

349

Time correlation functions in Vibration-Transit theory of liquid dynamics  

E-print Network

Within the framework of V-T theory of monatomic liquid dynamics, an exact equation is derived for a general equilibrium time correlation function. The purely vibrational contribution to such a function expresses the system's motion in one extended harmonic random valley. This contribution is analytically tractable and has no adjustable parameters. While this contribution alone dominates the thermodynamic properties, both vibrations and transits will make important contributions to time correlation functions. By way of example, the V-T formulation of time correlation functions is applied to the dynamic structure factor S(q,w). The vibrational contribution alone is shown to be in near perfect agreement with low-temperature molecular dynamics simulations, and a model simulating the transit contribution with three adjustable parameters achieves equally good agreement with molecular dynamics results in the liquid regime. The theory indicates that transits will broaden without shifting the Rayleigh and Brillouin peaks in S(q,w), and this behavior is confirmed by the MD calculations. We find the vibrational contribution alone gives the location and much of the width of the liquid-state Brillouin peak. We also discuss this approach to liquid dynamics compared with potential energy landscape formalisms and mode coupling theory, drawing attention to the distinctive features of our approach and to some potential energy landscape results which support our picture of the liquid state.

Eric D. Chisolm; Giulia De Lorenzi-Venneri; Duane C. Wallace

2005-11-30

350

Description of aromaticity with the help of vibrational spectroscopy: anthracene and phenanthrene.  

PubMed

A new approach is presented to determine ?-delocalization and the degree of aromaticity utilizing measured vibrational frequencies. For this purpose, a perturbation approach is used to derive vibrational force constants from experimental frequencies and calculated normal mode vectors. The latter are used to determine the local counterparts of the vibrational modes. Next, relative bond strength orders (RBSO) are obtained from the local stretching force constants, which provide reliable descriptors of CC and CH bond strengths. Finally, the RBSO values for CC bonds are used to establish a modified harmonic oscillator model and an aromatic delocalization index AI, which is split into a bond weakening (strengthening) and bond alternation part. In this way, benzene, naphthalene, anthracene, and phenanthrene are described with the help of vibrational spectroscopy as aromatic systems with a slight tendency of peripheral ?-delocalization. The 6.8 kcal/mol larger stability of phenanthrene relative to anthracene predominantly (84%) results from its higher resonance energy, which is a direct consequence of the topology of ring annelation. Previous attempts to explain the higher stability of phenanthrene via a maximum electron density path between the bay H atoms are misleading in view of the properties of the electron density distribution in the bay region. PMID:24308602

Kalescky, Robert; Kraka, Elfi; Cremer, Dieter

2014-01-01

351

Spontaneous noncollinear second harmonic generation in GUHP  

NASA Astrophysics Data System (ADS)

A detailed experimental investigation of the spontaneous noncollinear second harmonic generation in biaxial guanylurea(1 +) hydrogen phosphite (GUHP) crystal is reported. The number and shape of the resulting second harmonic hollow cones depend explicitly on the direction of propagation of the fundamental beam with respect to the optical axes and the type I or type II phase-matching lines, in agreement with theory and simple calculations. Spontaneous SHG allows an easy adjustment of the two-beam noncollinear SHG. Due to the large nonlinearity of GUHP, Fabry-Perot enhanced noncollinear SHG has been observed as well.

Kroupa, J.; Fridrichová, M.

2011-03-01

352

Optical harmonic generator  

DOEpatents

A pair of uniaxial birefringent crystal elements are fixed together to form a serially arranged, integral assembly which, alternatively, provides either a linearly or elliptically polarized second-harmonic output wave or a linearly polarized third-harmonic output wave. The extraordinary or e directions of the crystal elements are oriented in the integral assembly to be in quadrature (90/sup 0/). For a second-harmonic generation in the Type-II-Type-II angle tuned case, the input fundamental wave has equal amplitude o and e components. For a third-harmonic generation, the input fundamental wave has o and e components whose amplitudes are in a ratio of 2:1 (o:e reference first crystal). In the typical case of a linearly polarized input fundamental wave this can be accomplished by simply rotating the crystal assembly about the input beam direction by 10/sup 0/. For both second and third harmonic generation input precise phase-matching is achieved by tilting the crystal assembly about its two sensitive axeses (o).

Summers, M.A.; Eimerl, D.; Boyd, R.D.

1982-06-10

353

Aeroelastic analysis for helicopter rotors with blade appended pendulum vibration absorbers. Mathematical derivations and program user's manual  

NASA Technical Reports Server (NTRS)

Mathematical development is presented for the expanded capabilities of the United Technologies Research Center (UTRC) G400 Rotor Aeroelastic Analysis. This expanded analysis, G400PA, simulates the dynamics of teetered rotors, blade pendulum vibration absorbers and the higher harmonic excitations resulting from prescribed vibratory hub motions and higher harmonic blade pitch control. Formulations are also presented for calculating the rotor impedance matrix appropriate to these higher harmonic blade excitations. This impedance matrix and the associated vibratory hub loads are intended as the rotor blade characteristics elements for use in the Simplified Coupled Rotor/Fuselage Vibration Analysis (SIMVIB). Sections are included presenting updates to the development of the original G400 theory, and material appropriate to the user of the G400PA computer program. This material includes: (1) a general descriptionof the tructuring of the G400PA FORTRAN coding, (2) a detaild description of the required input data and other useful information for successfully running the program, and (3) a detailed description of the output results.

Bielawa, R. L.

1982-01-01

354

Good Vibrations  

NASA Technical Reports Server (NTRS)

A Small Business Innovation Research (SBIR) sponsorship from NASA's Dryden Flight Research Center, assisted MetroLaser, of Irvine, California, in the development of a self-aligned laser vibrometer system. VibroMet, capable of measuring surface vibrations in a variety of industries, provides information on the structural integrity and acoustical characteristics of manufactured products. This low-cost, easy-to-use sensor performs vibration measurement from distances of up to three meters without the need for adjustment. The laser beam is simply pointed at the target and the system then uses a compact laser diode to illuminate the surface and to subsequently analyze the reflected light. The motion of the surface results in a Doppler shift that is measured with very high precision. VibroMet is considered one of the many behind-the-scenes tools that can be relied on to assure the quality, reliability and safety of everything from airplane panels to disk brakes

2001-01-01

355

Converged vibrational energy levels and quantum mechanical vibrational partition function of ethane  

E-print Network

Converged vibrational energy levels and quantum mechanical vibrational partition function of ethane a combined valence-bond mo- lecular mechanics CVBMM potential energy surface.26 The calculations are carried function of ethane is calculated in the temperature range of 200­600 K using well-converged energy levels

Truhlar, Donald G

356

Temperature effects in first-principles solid state calculations of the chemical shielding tensor made simple.  

PubMed

We study the effects of atomic vibrations on the solid-state chemical shielding tensor using first principles density functional theory calculations. At the harmonic level, we use a Monte Carlo method and a perturbative expansion. The Monte Carlo method is accurate but computationally expensive, while the perturbative method is computationally more efficient, but approximate. We find excellent agreement between the two methods for both the isotropic shift and the shielding anisotropy. The effects of zero-point quantum mechanical nuclear motion are important up to relatively high temperatures: at 500 K they still represent about half of the overall vibrational contribution. We also investigate the effects of anharmonic vibrations, finding that their contribution to the zero-point correction to the chemical shielding tensor is small. We exemplify these ideas using magnesium oxide and the molecular crystals L-alanine and ?-aspartyl-L-alanine. We therefore propose as the method of choice to incorporate the effects of temperature in solid state chemical shielding tensor calculations using the perturbative expansion within the harmonic approximation. This approach is accurate and requires a computational effort that is about an order of magnitude smaller than that of dynamical or Monte Carlo approaches, so these effects might be routinely accounted for. PMID:25296790

Monserrat, Bartomeu; Needs, Richard J; Pickard, Chris J

2014-10-01

357

Temperature effects in first-principles solid state calculations of the chemical shielding tensor made simple  

NASA Astrophysics Data System (ADS)

We study the effects of atomic vibrations on the solid-state chemical shielding tensor using first principles density functional theory calculations. At the harmonic level, we use a Monte Carlo method and a perturbative expansion. The Monte Carlo method is accurate but computationally expensive, while the perturbative method is computationally more efficient, but approximate. We find excellent agreement between the two methods for both the isotropic shift and the shielding anisotropy. The effects of zero-point quantum mechanical nuclear motion are important up to relatively high temperatures: at 500 K they still represent about half of the overall vibrational contribution. We also investigate the effects of anharmonic vibrations, finding that their contribution to the zero-point correction to the chemical shielding tensor is small. We exemplify these ideas using magnesium oxide and the molecular crystals L-alanine and ?-aspartyl-L-alanine. We therefore propose as the method of choice to incorporate the effects of temperature in solid state chemical shielding tensor calculations using the perturbative expansion within the harmonic approximation. This approach is accurate and requires a computational effort that is about an order of magnitude smaller than that of dynamical or Monte Carlo approaches, so these effects might be routinely accounted for.

Monserrat, Bartomeu; Needs, Richard J.; Pickard, Chris J.

2014-10-01

358

Theoretical study of vibrational overtone spectroscopy and dynamics in methanol  

SciTech Connect

Experimentally observed couplings between OH and CH stretching modes in the high overtone region has been modelled successfully in terms of a curvilinear internal coordinate Hamiltonian including harmonic coupling between anharmonic OH and CH stretching oscillators and cubic Fermi resonance kinetic and potential energy couplings between CH stretches and HCH bends. The Hamiltonian matrices have been setup in block diagonal forms including only resonant states. The potential energy parameters have been optimized by the least squares method using experimental vibrational term values as data. The OH/CH stretch interaction parameter obtained agrees well with the one calculated by perturbation theory from a published ab initio harmonic force field. The model has reproduced well experimental band origins in the OH stretching overtone region and it has provided assignments for the bending overtones in the CH stretching fundamental region. Finally, a unitary transformation is found from the internal coordinate representation to the corresponding normal coordinate representation providing a set of normal coordinate parameters like diagonal anharmonicity parameters, Darling-Dennison resonance constants and cubic Fermi resonance force constants. These results confirm the experimental finding of energy redistribution between the OH and CH stretching modes on 100 fs time scale at 5{nu}{sub OH}.

Halonen, L.O.; Lehmann, K.K. [Princeton Univ., NJ (United States)

1996-12-31

359

Univalent ?-Harmonic Mappings  

NASA Astrophysics Data System (ADS)

We study mappings from 2 into 2 whose components are weak solutions to the elliptic equation in divergence form, div (??u)= 0, which we call ?-harmonic mappings. We prove sufficient conditions for the univalence, i.e., injectivity, of such mappings. Moreover we prove local bounds in BMO on the logarithm of the Jacobian determinant of such univalent mappings, thus obtaining the a.e. nonvanishing of their Jacobian. In particular, our results apply to ?-harmonic mapping associated with any periodic structure and therefore they play an important role in homogenization.

Alessandrini, Giovanni; Nesi, Vincenzo

360

Quantum chemical vibrational study, molecular property, FTIR, FT-Raman spectra, NBO, HOMO-LUMO energies and thermodynamic properties of 1-methyl-2-phenyl benzimidazole.  

PubMed

The solid phase FT-IR and FT-Raman spectra of 1-methyl-2-phenyl benzimidazole (MPBZ) have been recorded in the condensed state. In this work, experimental and theoretical study on the molecular structure, quantum chemical calculations of energies and vibrational wavenumbers of MPBZ is presented. The vibrational frequencies of the title compound were obtained theoretically by DFT/B3LYP calculations employing the standard 6-311+G(d,p) and 6-311++G(d,p) basis set for optimized geometry and were compared with Fourier transform infrared spectrum (FTIR) in the region of 4000-400 cm(-1) and with Fourier transform Raman spectrum in the region of 4000-100 cm(-1). Complete vibrational assignments, analysis and correlation of the fundamental modes for the title compound were carried out. The vibrational harmonic frequencies were scaled using scale factor, yielding a good agreement between the experimentally recorded and the theoretically calculated values. The study is extended to calculate the HOMO-LUMO energy gap, NBO, mapped molecular electrostatic potential (MEP) surfaces, polarizability, Mulliken charges and thermodynamic properties of the title compound. PMID:24785089

Karnan, M; Balachandran, V; Murugan, M; Murali, M K

2014-09-15

361

Effect of different molecular vibrational models on thermodynamic properties  

NASA Astrophysics Data System (ADS)

The full set of vibrational energies {E?} and the maximum vibrational quantum number ?max generated by an algebraic method (AM) are suggested to implement classical statistical thermodynamic formulae. This protocol is applied to study the molar vibrational internal energy, molar vibrational entropy and molar vibrational heat capacity of a macro-system consisting of the ground electronic state X1?+ of CO molecules. Comparisons of theoretical results with experimental measurements show that the AM statistical thermodynamic quantities are much better than those generated using beautiful analytical formulae that are based on the traditional simple harmonic oscillator (SHO) vibrational model, and that the suggested protocol can be extended to study statistical thermodynamic properties of any macro-diatomic system.

GuoYue, Liu; WeiGuo, Sun

2014-03-01

362

Design of a non-traditional dynamic vibration absorber.  

PubMed

A non-traditional dynamic vibration absorber is proposed for the minimization of maximum vibration velocity response of a vibrating structure. Unlike the traditional damped absorber configuration, the proposed absorber has a linear viscous damper connecting the absorber mass directly to the ground instead of the main mass. Optimum parameters of the proposed absorber are derived based on the fixed-point theory for minimizing the maximum vibration velocity response of a single-degree-of-freedom system under harmonic excitation. The extent of reduction in maximum vibration velocity response of the primary system when using the traditional dynamic absorber is compared with that using the proposed one. Under the optimum tuning condition of the absorbers, it is proved analytically that the proposed absorber provides a greater reduction in maximum vibration velocity response of the primary system than the traditional absorber. PMID:19640019

Cheung, Y L; Wong, W O

2009-08-01

363

Problems and Challenges Vibrations  

E-print Network

, but is not necessary for many standard measurements. Mounting all optical components on vibration insulation posts further reduced vibrations. Concerning the suppression of vibration-induced measurement problems58 Problems and Challenges Vibrations: One of the key problems for the bulge tester is vibration

Huston, Dryver R.

364

How do nuclei really vibrate or rotate  

SciTech Connect

By means of the adiabatic cranking model the properties of the current and velocity fields of nuclear quadrupole vibrations for even-even nuclei in the rare-earth region are investigated. BCS correlated wave functions based on the Nilsson single particle Hamiltonian have been used. The current fields are analyzed in terms of vector spherical harmonics. The realistic microscopic currents show a vortex structure not present in the classical irrotational flow. The microscopic origin of the vortex structure is investigated.

Andresen, H.G.; Kunz, J.; Mosel, U.; Mueller, M.; Schuh, A.; Wust, U.

1983-01-01

365

Rapid vibrational imaging with sum frequency generation microscopy  

PubMed Central

We demonstrate rapid vibrational imaging based on sum frequency generation (SFG) microscopy with a collinear excitation geometry. Using the tunable picosecond pulses from a high-repetition-rate optical parametric oscillator, vibrationally selective imaging of collagen fibers is achieved with submicrometer lateral resolution. We furthermore show simultaneous SFG and second harmonic generation imaging to emphasize the compatibility of the microscope with other nonlinear optical modalities. PMID:21964132

Raghunathan, Varun; Han, Yang; Korth, Olaf; Ge, Nien-Hui; Potma, Eric Olaf

2014-01-01

366

Harmonic Superspaces of Extended Supersymmetry. The Calculus of Harmonic Variables.  

National Technical Information Service (NTIS)

The main technical apparatus of the harmonic superspace approach to extended SUSY, the calculus of harmonic variables on homogeneous spaces of the SUSY automorphism groups, is presented in detail for N=2, 3, 4. The basic harmonics for the coset manifolds ...

E. Ivanov, S. Kalitzin Nguyen Ai Viet, V. Ogievetsky

1984-01-01

367

The origin of harmonic tremor at Old Faithful geyser  

NASA Astrophysics Data System (ADS)

VOLCANIC eruptions are sometimes accompanied by a characteristic type of seismicity known as harmonic tremor, in which the signal is dominated by discrete vibration frequencies1-4. This harmonic structure could reflect resonance behaviour in the excitation source4-6 or filtering of the seismic waves as they propagate through the surrounding rocks7-10 but complexity and variability in the properties of volcanic systems make it difficult to discriminate between such mechanisms. To address this question, we have analysed the source and propagation characteristics of seismicity at Old Faithful geyser (Yellowstone National Park), the cyclic behaviour and accessibility of which make it an ideal natural laboratory for studying harmonic tremor associated with near-surface sources. We find that sharp pressure pulses inside the water column trigger distinct seismic events that give rise to a harmonic ground response whose frequency varies spatially but not temporally. A superposition of these seismic events creates the appearance of continuous harmonic tremor. The absence of resonance within the water column suggests that the harmonic motion must arise from the interaction of the seismic waves with heterogeneities in the surrounding elastic medium-most probably a near-surface soft layer.

Kedar, Sharon; Sturtevant, Bradford; Kanamori, Hiroo

1996-02-01

368

Introducing Simple Harmonic Motion.  

ERIC Educational Resources Information Center

Explains the origin and significance of harmonic motion which is an important topic that has wide application in the world. Describes the phenomenon by using an auxiliary circle to help illustrate the key relationships between acceleration, displacement, time, velocity, and phase. (Contains 16 references.) (Author/YDS)

Roche, John

2002-01-01

369

A harmonic motion experiment  

NASA Astrophysics Data System (ADS)

We present a unit comprising theory, simulation and experiment for a body oscillating on a vertical spring, in which the simultaneous use of a force probe and an ultrasonic range finder enables one to explore quantitatively and understand many aspects of simple and damped harmonic motions.

Gluck, P.; Krakower, Zeev

2010-11-01

370

Calculated and experimental geometries and infrared spectra of metal tris-acetylacetonates: vibrational spectroscopy as a probe of molecular structure for ionic complexes. Part II  

NASA Astrophysics Data System (ADS)

Following on from our previous work on Sc, Fe, Cr, and Al (Part I; see J. Phys. Chem. A, 105 (2001) 238), the geometries and infrared spectra of the trivalent metal tris-acetylacetonate complexes (M[O 2C 5H 7] 3; M=Ti, V, Mn, Co) have been studied both experimentally and theoretically using nonlocal hybrid density functional theory with a split-valence plus polarization basis for the ligand and valence triple-? for the metal. Unlike the D 3 complexes studied in Part I, those of Ti, V and Mn are candidates for Jahn-Teller distortion due to fractional d-shell occupancy. Using scale factors transferred from Part I, our calculated frequencies are in very good agreement with experimentally observed fundamentals. Our investigation shows that the V and Mn complexes distort to C 2 ground states, but D 3 Ti tris-acetylacetonate is stable. Further investigation of the weak band observed around 800 cm -1 in the Fe complex (and present in almost all studied first-row transition metal tris-acetylacetonates), which we were unable to assign theoretically in Part I, supports the argument that this band is not a fundamental but is due to Fermi resonance.

Diaz-Acosta, Irina; Baker, Jon; Hinton, James F.; Pulay, Peter

2003-01-01

371

Prediction of vibrational frequencies of UO2(2+) at the CCSD(T) level.  

PubMed

Electronic structure calculations at the coupled cluster (CCSD(T)) and density functional theory levels with relativistic effective core potentials and large basis sets were used to predict the isolated uranyl ion frequencies. The effects of anharmonicity and spin-orbit corrections on the harmonic frequencies were calculated. The anharmonic effects are larger than the spin-orbit corrections, but both are small. The anharmonic effects decreased all the frequencies, whereas the spin-orbit corrections increased the stretches and decreased the bend. Overall, these two corrections decreased the harmonic asymmetric stretch frequency by 6 cm-1, the symmetric stretch by 3 cm-1, and the bend by 3 cm-1. The best calculated values for UO22+ for the asymmetric stretch, symmetric stretch, and bend were 1113, 1032, and 174 cm-1, respectively. The separation between the asymmetric and the symmetric stretch band origins was predicted to be 81 cm-1, which is consistent with experimental trends for substituted uranyls in solution and in the solid state. The anharmonic vibrational frequencies of the isoelectronic ThO2 molecule also were calculated and compared to experiment to calibrate the UO22+ results. PMID:18348547

Jackson, Virgil E; Craciun, Raluca; Dixon, David A; Peterson, Kirk A; de Jong, Wibe A

2008-05-01

372

Vibrational analysis of methylviologen  

SciTech Connect

The normal modes of vibration of methylviologen (1,1'-dimethyl-4,4'-bipyridyl dication, MV/sup 2 +/, or paraquat) and of its reduction product, the free-radical monocation MV/sup +/., have been computed by the Shimanouchi method. Calculated band wavenumbers are compared with those obtained from infrared, Raman, and resonance Raman spectra and these data are used as a basis for assignment of the observed spectra. Shifts in spectra between MV/sup 2 +/ and MV/sup +/. are interpreted and the derived force constants show increased bond order in the inter-ring bond in MV/sup +/.

Hester, R.E. (Univ. of York, England); Suzuki, S.

1982-11-11

373

The Impact of Static Disorder on Vibrational Resonance in a Ferroelectric Liquid Crystal  

Microsoft Academic Search

Vibrational resonance manifests itself in certain nonlinear systems that are subject to the action of a biharmonic force with very different frequencies. A proper frequency and\\/or amplitude of the high-frequency harmonic signal can lead to a resonantly enhanced response of the system with respect to the low frequency signal. In the present study we extent the concept of vibrational resonance

Marko Gosak; Matjaž Perc; Samo Kralj

2012-01-01

374

Downhole vibration sensing by vibration energy harvesting  

E-print Network

This thesis outlines the design of a prototype electromagnetic induction vibration energy harvesting device for use in a downhole environment. First order models of the necessary components for a generic vibration energy ...

Trimble, A. Zachary

2007-01-01

375

Vibrational intensity distributions in the photoelectron spectrum of hydrogen  

NASA Technical Reports Server (NTRS)

The intensity distribution over the H2(+) vibrational levels up to a vibrational quantum number of 15 has been measured for H2 photoelectron spectra at a photon wavelength of 584 A. The data show reasonable agreement with recent calculations only in the range of vibrational quantum numbers from 0 through 8; the higher levels are populated significantly lower than predicted by theory.

Gardner, J. L.; Samson, J. A. R.

1976-01-01

376

Classical dynamics of bend–stretch vibrational recurrence in HOD  

Microsoft Academic Search

Intramolecular dynamics of HOD was investigated by the classical trajectory method and detailed mechanisms of vibrational energy exchange were studied. The time evolution of mode energies in each vibrational mode along the trajectories was calculated. A periodic energy exchange, that is, a vibrational recurrence between the bending and OD stretching modes, is observed. The centrifugal force by the angular bending

Myung Soo Kim; Sang Tae Park; Soon Young Kwon; Hong Lae Kim

2000-01-01

377

Sampling microcanonical ensembles of trajectories using harmonic approximation in internal coordinates  

NASA Astrophysics Data System (ADS)

In this paper, we modify quasiclassical harmonic sampling of microcanonical ensembles of trajectories by using the curvilinear internal coordinates. The harmonic approximation in the curvilinear normal coordinates provides a more realistic description of the PES than in the conventional rectilinear ones at finite displacements. Therefore, the sampling of vibrations in the internal coordinates significantly improves the quality of the sampling in a block-box fashion, providing more realistic displacements and reducing the errors in the potential energy. In particular, the sampling of large-amplitude torsion vibrations, which is non-realistic in the Cartesian modes, becomes accurate or acceptable in the curvilinear modes.

Rybkin, Vladimir V.; Ekström, Ulf

2014-08-01

378

FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular geometry of butylated hydroxy toluene  

NASA Astrophysics Data System (ADS)

The FT-IR spectrum of 2,6-di-tert-butyl-4-methylphenol [butylated hydroxy toluene] was recorded in the region 4000-400 cm -1. The FT-Raman spectrum of butylated hydroxy toluene was also recorded in the region 3500-50 cm -1. The molecular structure and vibrational frequencies of butylated hydroxy toluene (BHT) have been investigated with combined experimental and theoretical study. Two stable conformers of the title compound were obtained from the result of geometry optimizations of these possible conformers. The conformer 1 is (approximately 2.6 kcal/mol) more stable than conformer 2. Geometry optimizations and vibrational frequency calculations were performed by BLYP and B3LYP methods using 6-31G(d), 6-31G(d,p) and 6-31+G(d,p) as basis sets. The scaled frequencies were compared with experimental spectrum and on the basis of this comparison; assignments of fundamental vibrational modes were examined. Comparison of the experimental spectra with harmonic vibrational wavenumbers indicates that B3LYP/6-31G(d) results are more accurate. Predicted electronic absorption spectra of BHT from TD-DFT calculation have been analyzed and compared with the experimental UV-vis spectrum. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule.

Chinna Babu, P.; Sundaraganesan, N.; Dereli, Ö.; Türkkan, E.

2011-08-01

379

Vibrational nonequilibrium effects on diatomic dissociation rates  

NASA Technical Reports Server (NTRS)

The collision-induced dissociation rate of diatomic molecules from a ladder of rotational and anharmonic vibrational states is developed, and the correction for vibrational nonequilibrium is considered. The result is similar to an analytic correction derived by Hammerling et al. (1959) for harmonic oscillators. An empirical correction algorithm suggested by Park (1987, 1990) gives similar results when vibrational temperature is comparable to kinetic temperature but underestimates the dissociation rate when vibrational temperature is small compared with the kinetic temperature. This algorithm uses an effective temperature in the experimentally determined Arrhenius expression for the rate coefficient, which is a weighted average of the vibrational and kinetic temperature, whereas theory indicates that kinetic temperature should appear only in the exponential term of the Arrhenius expression. Nevertheless, an effective temperature can always be found that will numerically duplicate the proper rate coefficient at any given condition, but a constant weighting factor cannot be expected to provide this. However, the algorithm can he adjusted to give reasonable results over a range of conditions if the geometric weighting factor is taken to be a simple linear function of the ratio of vibrational to kinetic temperature in the gas.

Hansen, C. F.

1993-01-01

380

Vibration measurements in the switched reluctance motor  

Microsoft Academic Search

Techniques for the measurement of vibrations in switched reluctance motors (SRMs) are given in this paper, together with experimental results. The measured results are compared to each other as well as with finite element calculated results, with good correlation

W. Cai; P. Pillay; Z. Tang; A. Omekanda

2001-01-01

381

Quantum chemical studies, vibrational analysis, molecular structure, first order hyper polarizability, NBO and HOMO-LUMO analysis of 3-hydroxybenzaldehyde and its cation  

NASA Astrophysics Data System (ADS)

FT-IR spectroscopy has been applied to investigate the potential nonlinear optical (NLO) material 3-hydroxybenzaldehyde (3HBA). The equilibrium geometry, Fukui function, harmonic vibrational frequencies, infrared intensities, and thermodynamic properties of 3HBA and its cation were calculated by HF/6-31G(d,p) and density functional theory B3LYP/6-31G(d,p), B3LYP/6-311++G(d,p) methods. The first order hyperpolarizability (?total) of this molecular system and related properties (?, ?, and ??) are calculated based on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond-like weak interaction has been analyzed using natural bond orbital (NBO) analysis by using B3LYP/6-311++G(d,p) method. The results show that electron density (ED) in the ?* and ?*anti-bonding orbitals and second-order delocalization energies E(2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The thermal stability of 3HBA and its cation is studied by the thermogravimetric analysis (TGA). The harmonic-vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR spectrum. The observed and the calculated frequencies are found to be in good agreement. The experimental spectrum also coincides satisfactorily with those of theoretically constructed spectrograms.

Muthu, S.; Prasath, M.

2013-11-01

382

Spherical Harmonics YLM Explorer  

NSDL National Science Digital Library

This is a Java applet that creates surface plots of the spherical harmonics. The user can set the L and m indices and the resolution of the plot. There is a restriction that L must be less than or equal to 5. Results are shown as either the amplitude of the function colored by the complex phase or the real part of the function illuminated by an external light source. Plots may be rotated in three dimensions.

Kraus, Martin

2005-04-16

383

Computing prime harmonic sums  

NASA Astrophysics Data System (ADS)

We discuss a method for computing sum_{p le x} 1/p , using time about x^{2/3} and space about x^{1/3} . It is based on the Meissel-Lehmer algorithm for computing the prime-counting function pi(x) , which was adapted and improved by Lagarias, Miller, and Odlyzko. We used this algorithm to determine the first point at which the prime harmonic sum first crosses 4.

Bach, Eric; Klyve, Dominic; Sorenson, Jonathan P.

2009-12-01

384

Metrics with harmonic spinors  

Microsoft Academic Search

We show that every closed spin manifold of dimensionn ? 3 mod 4 with a fixed spin structure can be given a Riemannian metric with harmonic spinors, i.e. the corresponding Dirac operator has a non-trivial kernel (Theorem A). To prove this we first compute the Dirac spectrum of the Berger spheresSn,n odd (Theorem 3.1). The second main ingredient is Theorem

Christian Bär

1996-01-01

385

Vibrational spectroscopy in high temperature dense fluids  

SciTech Connect

Coherent anti-Stokes Raman spectroscopy (CARS) in conjunction with a two-stage light-gas gun has been used to obtain vibrational spectra of shock-compressed liquid N{sub 2}, O{sub 2}, CO, and their mixtures, as well as liquid N{sub 2}O. The experimental spectra are compared to spectra calculated using a semiclassical model for CARS intensities to obtain vibrational frequencies, peak Raman susceptibilities, and linewidths. The derived spectroscopic parameters suggest thermal equilibrium of the vibrational populations is established in less than a few nanoseconds after shock passage. Vibrational temperatures obtained are compared to those derived from equation-of-state calculations. The variation of the vibrational frequency shift at pressure with species concentration in mixtures is investigated.

Moore, D.S.; Schmidt, S.C.

1992-01-01

386

Tracking harmonic notch filter  

SciTech Connect

An electronic filter for automatically tracking and removing harmonically related interfering electrical signals such as power-line interference harmonics without attenuating other signals of interest even though the signals are frequency stable and/or near the interference signal frequencies. The filter comprises a very narrow band electronic commutated capacitor-bank comb-notch filter driven by a counter/decoder circuit which is in turn driven by a phase locked loop. The filter also comprises two narrow-band analog filters tuned to the two lowest harmonics of the interfering signal. The summed output of these two filters is applied to the input of the phase-locked loop. The phase-locked loop locks to the proper multiple of the interfering signal and drives the comb notch filter at a frequency which causes it to generate notches at unit multiples of the fundamental of the interference frequency. This action is continuous such that center frequencies of the notches are automatically adjusted to compensate for small variations in the interference frequency.

Eno, F.

1989-03-20

387

Computing vibrational spectra from ab initio molecular dynamics.  

PubMed

We review several methods for the calculation of vibrational spectra from ab initio molecular dynamics (AIMD) simulations and we present a new implementation in the trajectory analyzer TRAVIS. In particular, we show mass-weighted power spectra, infrared spectra, and Raman spectra with corresponding depolarization ratios, which are based on time-correlation functions of velocities, dipole moments, and polarizabilities, respectively. Using the four organic molecules methanol, acetone, nitromethane, and pinacol as test systems, we compare the spectra from AIMD simulations of the isolated molecules in gas phase to static calculations relying on the harmonic approximation and to experimental spectra recorded in a nonpolar solvent. The AIMD approach turns out to give superior results when anharmonicity effects are of particular importance. Using the example of methanol, we demonstrate the application to bulk phase systems, which are not directly accessible by static calculations, but for which the AIMD spectra also provide a very good approximation to experimental data. Finally, we investigate the influence of simulation time and temperature in the AIMD on the resulting spectra. PMID:23416970

Thomas, Martin; Brehm, Martin; Fligg, Reinhold; Vöhringer, Peter; Kirchner, Barbara

2013-05-14

388

Iron Loss Analysis of IPM Motor Considering Carrier Harmonics  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the iron loss of interior permanent magnet motors driven by PWM inverters using electromagnetic field analysis. Following 4 methods are applied: (1) Current input finite element method neglecting the carrier harmonics. (2) Voltage input finite element analysis neglecting carrier harmonics. (3) Current input finite element method with the measured armature current waveforms including the carrier harmonics. (4) Voltage input finite element method with the theoretical voltage waveforms of the PWM inverter. The calculated results are compared with the experimental ones. It is clarified that the accuracy of the calculated results are improved by considering the carrier harmonics and that the method (4) can estimate the iron loss of the IPM motor accurately before manufacturing. The variation of the iron loss components due to the driving condition is also clarified.

Yamazaki, Katsumi; Seto, Yoshiaki; Tanida, Makoto

389

Second harmonic effect on geodesic modes in tokamak plasmas  

SciTech Connect

Results of a kinetic treatment of Geodesic Acoustic Modes (GAMs) that fully takes into account ion parallel dynamics, including the magnetic field component, are presented. The finite-orbit-width (FOW) parameter is considered in the calculation of the second harmonic effect on GAMs. For larger values of the FOW parameter, it is shown that dispersive effects related to the m = 2 harmonics is the cause of the mode frequency splitting and the modes appear due to the interaction with the ion sound mode. Furthermore, the modes may have enhanced damping rates due to second harmonic Landau damping.

Elfimov, A. G.; Galvão, R. M. O. [Institute of Physics, University of São Paulo, São Paulo 05508-090 (Brazil)] [Institute of Physics, University of São Paulo, São Paulo 05508-090 (Brazil); Smolyakov, A. I. [University of Saskatchewan, 116 Science Place, Saskatoon S7N 5E2 (Canada) [University of Saskatchewan, 116 Science Place, Saskatoon S7N 5E2 (Canada); Institute of Tokamak Physics, NRC “Kurchatov Institute,” 123182 Moscow (Russian Federation); Melnikov, A. V. [Institute of Tokamak Physics, NRC “Kurchatov Institute,” 123182 Moscow (Russian Federation)] [Institute of Tokamak Physics, NRC “Kurchatov Institute,” 123182 Moscow (Russian Federation)

2013-05-15

390

Second harmonic effect on geodesic modes in tokamak plasmas  

NASA Astrophysics Data System (ADS)

Results of a kinetic treatment of Geodesic Acoustic Modes (GAMs) that fully takes into account ion parallel dynamics, including the magnetic field component, are presented. The finite-orbit-width (FOW) parameter is considered in the calculation of the second harmonic effect on GAMs. For larger values of the FOW parameter, it is shown that dispersive effects related to the m = 2 harmonics is the cause of the mode frequency splitting and the modes appear due to the interaction with the ion sound mode. Furthermore, the modes may have enhanced damping rates due to second harmonic Landau damping.

Elfimov, A. G.; Smolyakov, A. I.; Melnikov, A. V.; Galvão, R. M. O.

2013-05-01

391

Molecular structure, vibrational spectra, NBO, UV and first order hyperpolarizability, analysis of 4-Chloro-DL-phenylalanine by density functional theory  

NASA Astrophysics Data System (ADS)

The Fourier transform infrared (4000-400 cm-1) and Fourier transform Raman (3500-50 cm-1) spectra of 4-Chloro-DL-phenylalanine (4CLPA) were recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational wavenumbers were investigated with the help of density functional theory (DFT) method using B3LYP/6-31G(d,p) as basis set. The observed vibrational wavenumbers were compared with the calculated results. Natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. Predicted electronic absorption spectra from TD-DFT calculation have been analyzed comparing with the UV-Vis (200-800 nm) spectrum. The effects of chlorine and ethylene group substituent in benzene ring in the vibrational wavenumbers have been analyzed. The HOMO-LUMO energy gap explains the charge interaction taking place within the molecule. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of 4CLPA were calculated. The Chemical reactivity and chemical potential of 4CLPA is calculated. In addition, molecular electrostatic potential (MEP), frontier molecular orbital (FMO) analysis were investigated using theoretical calculations.

Govindarasu, K.; Kavitha, E.

2014-12-01

392

Noncontact Electromagnetic Vibration Source  

NASA Technical Reports Server (NTRS)

Metal aircraft skins scanned rapidly in vibration tests. Relatively simple combination of permanent magnets and electromagnet serves as noncontact vibration source for nondestructive testing of metal aircraft skins. In test, source excites vibrations, and vibration waveforms measured, then analyzed for changes in resonances signifying cracks and other flaws.

Namkung, Min; Fulton, James P.; Wincheski, Buzz A.

1994-01-01

393

Calculations of vibrational signatures for coherent LADAR  

Microsoft Academic Search

The results of a computer program modeling the output of a monostatic CW coherent laser radar for a limited class of targets and a limited set of possible target motions are presented. The model satisfactorily accounts for the data taken for targets undergoing pure rotation. This includes range Doppler images even though the range resolution capability is added ad hoc

Jere S. Singleton; William L. Gamble

1989-01-01

394

Vibration and noise analysis of a gear transmission system  

NASA Technical Reports Server (NTRS)

This paper presents a comprehensive procedure to predict both the vibration and noise generated by a gear transmission system under normal operating conditions. The gearbox vibrations were obtained from both numerical simulation and experimental studies using a gear noise test rig. In addition, the noise generated by the gearbox vibrations was recorded during the experimental testing. A numerical method was used to develop linear relationships between the gearbox vibration and the generated noise. The hypercoherence function is introduced to correlate the nonlinear relationship between the fundamental noise frequency and its harmonics. A numerical procedure was developed using both the linear and nonlinear relationships generated from the experimental data to predict noise resulting from the gearbox vibrations. The application of this methodology is demonstrated by comparing the numerical and experimental results from the gear noise test rig.

Choy, F. K.; Qian, W.; Zakrajsek, J. J.; Oswald, F. B.

1993-01-01

395

Calculation of anharmonic OH phonon dispersion curves for the Mg(OH)2 crystal.  

PubMed

Anharmonic OH phonon dispersion curves have been calculated for the Mg(OH)(2) crystal. A crystal Hamiltonian was set up for the vibrational problem, where the coordinates consists of the bond lengths of two hydroxide ions in the central unit cell. Its two-dimensional potential energy surface was constructed from first principle calculations within the density functional theory approximation. Dispersion curves were calculated by diagonalizing the Hamiltonian in a basis of singly excited crystal functions. The single particle functions used to construct the crystal states were taken from a Morse oscillator basis set. These well chosen functions made it possible to restrict calculations to include only very few functions, which greatly contributed to a transparent presentation of the underlying theory. All calculations could be done analytically except for the calculation of a few integrals. We have compared our results with those of a series of harmonic lattice dynamics calculations and have found that the anharmonicity shifts the IR and Raman dispersion curves downward appreciably and slightly changes the energy differences between both curves. From an analysis of the harmonic results we conclude that incorporating the coupling between OH stretching motion and the motion of their centers of mass will appreciably change the overall features of the dispersion curves. Extension of the anharmonic model along these lines will cause no problem to the theoretical approach presented in this paper. PMID:20649321

Mitev, Pavlin D; Hermansson, Kersti; Briels, Wim J

2010-07-21

396

Vibrational dynamics of DNA. I. Vibrational basis modes and couplings.  

PubMed

Carrying out density functional theory calculations of four DNA bases, base derivatives, Watson-Crick (WC) base pairs, and multiple-layer base pair stacks, we studied vibrational dynamics of delocalized modes with frequency ranging from 1400 to 1800 cm(-1). These modes have been found to be highly sensitive to structure fluctuation and base pair conformation of DNA. By identifying eight fundamental basis modes, it is shown that the normal modes of base pairs and multilayer base pair stacks can be described by linear combinations of these vibrational basis modes. By using the Hessian matrix reconstruction method, vibrational coupling constants between the basis modes are determined for WC base pairs and multilayer systems and are found to be most strongly affected by the hydrogen bonding interaction between bases. It is also found that the propeller twist and buckle motions do not strongly affect vibrational couplings and basis mode frequencies. Numerically simulated IR spectra of guanine-cytosine and adenine-thymine bases pairs as well as of multilayer base pair stacks are presented and described in terms of coupled basis modes. It turns out that, due to the small interlayer base-base vibrational interactions, the IR absorption spectrum of multilayer base pair system does not strongly depend on the number of base pairs. PMID:16999491

Lee, Chewook; Park, Kwang-Hee; Cho, Minhaeng

2006-09-21

397

Vibrational dynamics of DNA. I. Vibrational basis modes and couplings  

NASA Astrophysics Data System (ADS)

Carrying out density functional theory calculations of four DNA bases, base derivatives, Watson-Crick (WC) base pairs, and multiple-layer base pair stacks, we studied vibrational dynamics of delocalized modes with frequency ranging from 1400to1800cm-1. These modes have been found to be highly sensitive to structure fluctuation and base pair conformation of DNA. By identifying eight fundamental basis modes, it is shown that the normal modes of base pairs and multilayer base pair stacks can be described by linear combinations of these vibrational basis modes. By using the Hessian matrix reconstruction method, vibrational coupling constants between the basis modes are determined for WC base pairs and multilayer systems and are found to be most strongly affected by the hydrogen bonding interaction between bases. It is also found that the propeller twist and buckle motions do not strongly affect vibrational couplings and basis mode frequencies. Numerically simulated IR spectra of guanine-cytosine and adenine-thymine bases pairs as well as of multilayer base pair stacks are presented and described in terms of coupled basis modes. It turns out that, due to the small interlayer base-base vibrational interactions, the IR absorption spectrum of multilayer base pair system does not strongly depend on the number of base pairs.

Lee, Chewook; Park, Kwang-Hee; Cho, Minhaeng

2006-09-01

398

Spectroscopic (FT-IR, FT-Raman) investigations and quantum chemical calculations of 4-hydroxy-2-oxo-1,2-dihydroquinoline-7-carboxylic acid.  

PubMed

Quinoline derivatives have good nonlinear optical properties and have been extensively studied due to their great potential application in the field of organic light emitting diodes. Quantum chemical calculations of the equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman activities of 4-hydroxy-2-oxo-1,2-dihydroquinoline-7-carboxylic acid in the ground state were reported. Potential energy distribution of normal modes of vibrations was done using GAR2PED program. The synthesis, (1)H NMR and PES scan results are also discussed. 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 hyperconjugative interaction and charge delocalization has been analyzed using NBO analysis. The calculated geometrical parameters are in agreement with that of similar derivatives. PMID:24287049

Ulahannan, Rajeev T; Panicker, C Yohannan; Varghese, Hema Tresa; Van Alsenoy, C; Musiol, Robert; Jampilek, Josef; Anto, P L

2014-01-01

399

The use of statistical characteristics of reducer vibrations as diagnostic symptoms  

NASA Technical Reports Server (NTRS)

The results of a statistical analysis of the vibrations of the experimental RS-1 reducer stand, with a spiral-gear transmission, operating on a closed circuit, are presented. The analysis was carried out on the Minsk-2 and Minsk-32 digital computers, with two-channel analog-digital converter, built in the Institute of the Science of Mechanics. Two-dimensional distribution patterns, conditional dispersions and dispersion ratios were calculated. The octave-band-filtered first harmonics of the tooth frequency f sub z of the vibrations at two different measurement points were considered as the components of the vibration process to be analyzed. The regression lines, corresponding to different values of the loading torque, are presented. Since it was not the gear drive parameters which were determined by diagnostic methods, but the characteristics most sensitive to change in state of the object of the investigation, the loading torque, which is the simplest and most accessible for measurement, was chosen as the condition parameter.

Balitskiy, F. Y.; Genkin, M. D.; Ivanova, M. A.; Sokolova, A. G.

1973-01-01

400

Vibrational study of intramolecular hydrogen bonding in o-hydroxybenzoyl compounds  

NASA Astrophysics Data System (ADS)

The vibrational study of a set of o-hydroxybenzoyl compounds (salicylaldehyde, o-hydroxyacetophenone, methyl salicylate and salicylamide) and their parent compounds (phenol, benzaldehyde, acetophenone, methyl benzoate and benzamide) has been performed by infrared (IR) measurements and by quantum chemical calculations using B3LYP density functional in conjunction with 6-31G ?? and 6-311++G(3df, 2p) basis sets. The assignment of the infrared bands results unequivocal for most cases, including those signals in which the motion of the intramolecular hydrogen bond (IMHB) is involved. The analysis of the IR spectra for the deuterated derivatives was proved to be a very useful tool for this purpose. A model based on isotopically substituted benzenes was used for classifying the phenyl ring movements of the molecules studied. The results obtained show the suitability and limitation of the harmonic treatment using B3LYP method to describe the characteristic IMHB vibrations. Vibrational data are analyzed in order to obtain information about the nature of the hydrogen bonding interaction in this family of compounds. Finally, the available empirical relationships to approximate the IMHB energy from experimental spectroscopic data are revised in view of the new theoretical results.

Palomar, J.; De Paz, J. L. G.; Catalán, J.

1999-07-01

401

Full dimensional Franck-Condon factors for the acetylene A? (1)Au-X? ?g+1 transition. II. Vibrational overlap factors for levels involving excitation in ungerade modes.  

PubMed

A full-dimensional Franck-Condon calculation has been applied to the A? (1)Au-X? ?g+1 transition in acetylene in the harmonic normal mode basis. Details of the calculation are discussed in Part I of this series. To our knowledge, this is the first full-dimensional Franck-Condon calculation on a tetra-atomic molecule undergoing a linear-to-bent geometry change. In the current work, the vibrational intensity factors for levels involving excitation in ungerade vibrational modes are evaluated. Because the Franck-Condon integral accumulates away from the linear geometry, we have been able to treat the out-of-plane component of trans bend (?4 ('')) in the linear X? state in the rotational part of the problem, restoring the ? Euler angle and the a-axis Eckart conditions. A consequence of the Eckart conditions is that the out-of-plane component of ?4 ('') does not participate in the vibrational overlap integral. This affects the structure of the coordinate transformation and the symmetry of the vibrational wavefunctions used in the overlap integral, and results in propensity rules involving the bending modes of the X? state that were not previously understood. We explain the origin of some of the unexpected propensities observed in IR-UV laser-induced fluorescence spectra, and we calculate emission intensities from bending levels of the A? state into bending levels of the X? state, using normal bending mode and local bending mode basis sets. Our calculations also reveal Franck-Condon propensities for the Cartesian components of the cis bend (?5 ('')), and we predict that the best A?-state vibrational levels for populating X?-state levels with large amplitude bending motion localized in a single C-H bond (the acetylene?vinylidene isomerization coordinate) involve a high degree of excitation in ?6 (') (cis-bend). Mode ?4 (') (torsion) populates levels with large amplitude counter-rotational motion of the two hydrogen atoms. PMID:25296804

Park, G Barratt; Baraban, Joshua H; Field, Robert W

2014-10-01

402

Finite element 2D steady-state time harmonic field analysis of induction motor  

Microsoft Academic Search

This work describes a method of calculating the steady state harmonic field distribution of an induction motor. A finite element based model, which predicts the magnetic field throughout in induction motor during steady state conditions, is established. The harmonic components of magnetic field and the spatial distribution corresponding to each of the frequency components are calculated for an induction motor

Ajay Kumar; Sanjay Marwaha; Anupama Marwaha

2004-01-01

403

Determination of material properties by use of third-harmonic generation microscopy  

Microsoft Academic Search

The fundamental features of third-harmonic generation microscopy are examined both theoretically and experimentally, and the technique is applied to the characterization of layered structures. Measurements and model calculations have been performed of the third-harmonic yield generated from homogeneous layers. Model calculations based on the paraxial approximation show good agreement with the experimental results, despite the conditions of high numerical aperture.

J. M. Schins; Th. Schrama; J. Squier; G. J. Brakenhoff; M. Muller

2002-01-01

404

Towards automated biomedical ontology harmonization.  

PubMed

The use of biomedical ontologies is increasing, especially in the context of health systems interoperability. Ontologies are key pieces to understand the semantics of information exchanged. However, given the diversity of biomedical ontologies, it is essential to develop tools that support harmonization processes amongst them. Several algorithms and tools are proposed by computer scientist for partially supporting ontology harmonization. However, these tools face several problems, especially in the biomedical domain where ontologies are large and complex. In the harmonization process, matching is a basic task. This paper explains the different ontology harmonization processes, analyzes existing matching tools, and proposes a prototype of an ontology harmonization service. The results demonstrate that there are many open issues in the field of biomedical ontology harmonization, such as: overcoming structural discrepancies between ontologies; the lack of semantic algorithms to automate the process; the low matching efficiency of existing algorithms; and the use of domain and top level ontologies in the matching process. PMID:24851964

Uribe, Gustavo A; Lopez, Diego M; Blobel, Bernd

2014-01-01

405

Imaging velocities of a vibrating object by stroboscopic sideband holography  

NASA Astrophysics Data System (ADS)

We propose here to combine sideband holography with stroboscopic illumination synchronized with the vibration of an object. By sweeping the optical frequency of the reference beam such a way the holographic detection is tuned on the successive sideband harmonic ranks, we are able to image the instantaneous velocities of the object. Since the stroboscopic illumination is made with an electronic device, the method is compatible with fast (up to several MHz) vibration motions. The method is demonstrated with a vibrating clarinet reed excited sinusoidally at 2 kHz, and a stroboscopic illumination with cyclic ratio 0.15. Harmonic rank up to n = $\\pm$100 are detected, and a movie of the instantaneous velocities is reported.

Verpillat, F.; Joud, F.; Atlan, M.; Gross, M.

2012-09-01

406

Molecular and vibrational structure of tetroxo d0 metal complexes in their excited states. a study based on time-dependent density functional calculations and Franck-Condon theory.  

PubMed

We have applied time dependent density functional theory to study excited state structures of the tetroxo d(0) transition metal complexes MnO(4)(-), TcO(4)(-), RuO(4), and OsO(4). The excited state geometry optimization was based on a newly implemented scheme [Seth et al. Theor. Chem. Acc. 2011, 129, 331]. The first excited state has a C(3v) geometry for all investigated complexes and is due to a "charge transfer" transition from the oxygen based HOMO to the metal based LUMO. The second excited state can uniformly be characterized by "charge transfer" from the oxygen HOMO-1 to the metal LUMO with a D(2d) geometry for TcO(4)(-), RuO(4), and OsO(4) and two C(2v) geometries for MnO(4)(-). It is finally found that the third excited state of MnO(4)(-) representing the HOMO to metal based LUMO+1 orbital transition has a D(2d) geometry. On the basis of the calculated excited state structures and vibrational modes, the Franck-Condon method was used to simulate the vibronic structure of the absorption spectra for the tetroxo d(0) transition metal complexes. The Franck-Condon scheme seems to reproduce the salient features of the experimental spectra as well as the simulated vibronic structure for MnO(4)(-) generated from an alternative scheme [Neugebauer J. J. Phys. Chem. A 2005, 109, 1168] that does not apply the Franck-Condon approximation. PMID:22280538

Jose, Linta; Seth, Michael; Ziegler, Tom

2012-02-23

407

Application of surface-harmonics code SUHAM-U and Monte-Carlo code UNK-MC for calculations of 2D light water benchmark-experiment VENUS-2 with UO{sub 2} and MOX fuel  

SciTech Connect

Verification of the SUHAM-U code has been carried out by the calculation of two-dimensional benchmark-experiment on critical light-water facility VENUS-2. Comparisons with experimental data and calculations by Monte-Carlo code UNK with the same nuclear data library B645 for basic isotopes have been fulfilled. Calculations of two-dimensional facility were carried out with using experimentally measured buckling values. Possibility of SUHAM code application for computations of PWR reactor with uranium and MOX fuel has been demonstrated. (authors)

Boyarinov, V. F.; Davidenko, V. D.; Nevinitsa, V. A.; Tsibulsky, V. F. [Russian Research Center Kurchatov Inst., Inst. of Nuclear Reactors, 123182, Moscow (Russian Federation)

2006-07-01

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Harmonics and instabilities in switching circuits  

SciTech Connect

Over the last couple of years there has been significant activity in the