Force field of acetic acid: use of CNDO/force calculations

The redundancy-free internal valence force field of monomeric acetic acid is evaluated using CNDO/force calculations and least-squares refinement. The initial force field is set up by taking the interaction and bending force constants from CNDO force field and transferring the stretching force constants from the force fields of chemically related molecules. Vibrational frequencies of monomeric CH3COOH, CH3COOD, CD3COOH, and CD3COOD are used to refine the force constants. The experimental force field thus obtained is found to be reasonable when compared to the force fields of related molecules as well as on the basis of the frequency fits and potential energy distributions.

Download Full-text

Schwingungsberechnungen des Hexathiometadiphosphatanions P2S62-

Zeitschrift für Naturforschung A ◽

10.1515/zna-1988-0515 ◽

1988 ◽

Vol 43 (5) ◽

pp. 494-496 ◽

Cited By ~ 2

Author(s):

Lothar Ohse ◽

Wolfgang Brockner

Keyword(s):

Potential Energy ◽

Energy Distribution ◽

Force Field ◽

Field Potential ◽

Normal Coordinate Analysis ◽

Force Constants ◽

Potential Energy Distribution ◽

Normal Coordinate ◽

Mean Amplitudes Of Vibration ◽

Initial Force

A normal coordinate analysis for the Hexathiometadiphosphate anion P2S62- was performed, based on a simple initial force field. The force field was refined by adjusting the symmetry force constants to approximate the observed frequencies. The final force field, potential energy distribution (PED) and mean amplitudes of vibration are also given. Based on the normal coordinate analysis a new assignment of the P2S62- frequencies is proposed.

Download Full-text

Vibrational Potential Energy Distributions and Coriolis Coefficients for Extremal Force Constants in Bent XY2, Pyramidal XY3, and Tetrahedral XY4 Molecules

Zeitschrift für Naturforschung A ◽

10.1515/zna-1970-0212 ◽

1970 ◽

Vol 25 (2) ◽

pp. 217-221 ◽

Cited By ~ 1

Author(s):

D.E. Freeman

Keyword(s):

Hydrogen Atom ◽

Potential Energy ◽

Force Fields ◽

Force Constants ◽

Energy Distributions

Abstract For 27 molecules with approximately extremal force fields, an empirical distinction between hydrides and non-hydrides is linked, via the comparison of calculated and observed Coriolis coefficients, to a difference, based ultimately on the relative lightness of the hydrogen atom, in the potential energy distributions of hydrides and non-hydrides. The potential energy criteria of Becher and Ballein are compared to those corresponding to extremal diagonal force constants. Coriolis coefficients for the model of progressive rigidity are mostly in rough agreement with those observed.

Download Full-text

On the Calculation of the Force Constants for Halides AX4n (Td). Using an Empirical Constraint F33 (F2)/F11 (A1) = Constant for Similar Molecules and Ions

Zeitschrift für Naturforschung A ◽

10.1515/zna-1975-0509 ◽

1975 ◽

Vol 30 (5) ◽

pp. 627-635 ◽

Cited By ~ 1

Author(s):

A. Alix ◽

C. Cerf ◽

S. N. Rai

Keyword(s):

Force Field ◽

General Formula ◽

Force Fields ◽

Force Constants ◽

Valence Force ◽

Valence Force Field

Abstract An empirical constraint for the determination of the force constants of a General Valence Force Field for the tetrahedral halides with the general formula AX4n (where A = an element of the groupe II, III, IV, V and VI; X = F, Cl, Br and I and n = +1, 0, -1 and -2) is presented. The model is defined by a constant value of the parameter p= (ft -ftt) / (ft + 3ftt). The optimum value, p = 0.73, obtained for the mixed halides of chlorobromomethane is compared with those calculated from other force fields commonly used.

Download Full-text

Molecular Force Fields of Tungsten and Uranium Hexachlorides

Zeitschrift für Naturforschung A ◽

10.1515/zna-1972-0422 ◽

1972 ◽

Vol 27 (4) ◽

pp. 700-701 ◽

Cited By ~ 1

Author(s):

M.N. Avasthi ◽

M.L. Mehta

Keyword(s):

Force Field ◽

Force Fields ◽

Field Studies ◽

Force Constants ◽

Least Square ◽

Valence Force ◽

Valence Force Field ◽

Weighted Least Square ◽

Molecular Force ◽

Molecular Force Field

Abstract Molecular force field studies of tungsten and uranium hexa-chloride have been carried out using the Urey-Bradley force field (UBFF) and the orbital valence force field (OVFF). Weighted least square adjustment has been used to fit the observed frequencies. Comments are also made on the suit-ability of the force fields used. The trends in stretching force constants have been discussed.

Download Full-text

Schwingungsspektren und Kraftkonstanten der Hexacyano-Komplexe des Mangan(I), Technetium(I) und Rhenium(I) / Vibrational Spectra and Force Constants of the Hexacyano Complexes of Mangan(l), Technicium(I) and Rhenium(l)

Zeitschrift für Naturforschung A ◽

10.1515/zna-1972-8-905 ◽

1972 ◽

Vol 27 (8-9) ◽

pp. 1193-1196 ◽

Cited By ~ 8

Author(s):

W. Krasser ◽

K. Schwochau

Keyword(s):

Force Field ◽

Raman Spectra ◽

Vibrational Spectra ◽

Point Group ◽

Force Constants ◽

Irreducible Representations ◽

Infrared And Raman Spectra ◽

Valence Force ◽

Valence Force Field ◽

Complex Salts

The infrared and Raman spectra of the complex salts K5[Mn(CN)6], K5[Tc(CN)6] and K5[Re(CN)s] have been recorded in the range from 4000 to 40 cm-1. All expected fundamental vibrations have been observed and could be assigned to the irreducible representations of the symmetry point group Oh . The calculation of the force constants is based on the concept of the generalized valence force field. The low CN-valence force constants indicate the relatively strong Π-bonding character of the metal carbon bond, which is especially pronounced for K5[Tc(CN)6).

Download Full-text

The Vibrational Spectrum and Urey-Bradley Force Constants of the Trifluoromethyltrifluoroborate(1-) Anion

Applied Spectroscopy ◽

10.1366/000370273774333678 ◽

1973 ◽

Vol 27 (3) ◽

pp. 209-213 ◽

Cited By ~ 3

Author(s):

John F. Jackovitz ◽

Charles E. Falletta ◽

James C. Carter

Keyword(s):

Potential Energy ◽

Vibrational Spectrum ◽

Energy Distribution ◽

Force Field ◽

Raman Spectra ◽

Normal Modes ◽

Force Constants ◽

Potential Energy Distribution ◽

Infrared And Raman Spectra ◽

Normal Coordinate

Infrared and Raman spectra for (K+) (CF3BF3−) have been obtained from 4000 to 50 cm−1. Spectral assignments were made on the basis of C3v symmetry using both 10B and 11B compounds. In addition, a normal coordinate analysis was performed to obtain the potential energy distribution of the normal modes. A Urey-Bradley type force field was used, and force constants obtained for the CF3 and BF3 groupings were compared to those in C2F6 and BF4−.

Download Full-text

Generalized valence force field force constants and mean-square amplitudes of vibration of some trigonal bipyramidal XY5 molecules calculated by the logarithmic steps method

Journal of the Chemical Society A Inorganic Physical Theoretical ◽

10.1039/j19710001747 ◽

1971 ◽

pp. 1747 ◽

Cited By ~ 5

Author(s):

E. J. L. Wendling ◽

S. Mahmoudi ◽

H. J. MacCordick

Keyword(s):

Force Field ◽

Force Constants ◽

Mean Square ◽

Valence Force ◽

Field Force ◽

Valence Force Field ◽

Trigonal Bipyramidal

Download Full-text

Notizen:Schwingungseigenschaften des TeO42- -Ions/ Vibrational Properties of the TeO42--Ion

Zeitschrift für Naturforschung A ◽

10.1515/zna-1978-1018 ◽

1978 ◽

Vol 33 (10) ◽

pp. 1226-1227

Author(s):

Enrique J. Baran

Keyword(s):

Force Field ◽

Related Species ◽

Force Constants ◽

Vibrational Properties ◽

Bond Orders ◽

Mean Amplitudes Of Vibration ◽

Valence Force ◽

Valence Force Field ◽

Complete Assignment

Abstract A complete assignment of the fundamental vibrations of the tetrahedral TeO42- ion is proposed and its principal force constants have been calculated using the modified valence force field. Mean amplitudes of vibration and bond orders are also estimated. The results are briefly discussed and some comparisons with related species are made.

Download Full-text

On the application of OVFF to MX6 type ions

Zeitschrift für Naturforschung A ◽

10.1515/zna-1972-0527 ◽

1972 ◽

Vol 27 (5) ◽

pp. 867-869 ◽

Cited By ~ 2

Author(s):

J. N. Rai ◽

S. N. Tiwary ◽

S. N. Rai

Keyword(s):

Force Field ◽

Point Group ◽

Force Constants ◽

Valence Force ◽

Valence Force Field

AbstractForce constants for nine ions belonging to Oh point group have been evaluated by using Orbital Valence Force Field. The constants have been compared with their values obtained by using Urey-Bradley Force Field. The validity of the two methods has been discussed

Download Full-text

Harmonie Force Fields and Bond Orders for Naphthalene, Anthracene, Biphenylene and Perylene with Mean Amplitudes for Perylene

Zeitschrift für Naturforschung A ◽

10.1515/zna-1978-0110 ◽

1978 ◽

Vol 33 (1) ◽

pp. 45-54 ◽

Cited By ~ 43

Author(s):

J. C. Whitmer ◽

S. J. Cyvin ◽

B. N. Cyvin

Keyword(s):

Force Field ◽

Force Fields ◽

Field Approximation ◽

Force Constants ◽

Bond Orders ◽

Mean Amplitudes Of Vibration ◽

Complete Set ◽

First Time ◽

The Relationship ◽

Good Agreement

Complete normal coordinate analyses were performed for naphthalene, anthracene, biphenylene and perylene, starting from a simple force field with seven adjustable force constants. A relationship between bond orders and carbon-carbon stretching force constants was deduced from: (a) bond distances as a function of bond orders, (b) a version of Badger's rule relating stretching force constants to the bond distances. The relationship was used to modify the initial seven-parameter force field, and the vibrational frequencies calculated from both the initial and modified force fields are discussed. In general the simple force field approximation produces sets of frequencies in remarkably good agreement with experimental assignments. The force field approximation failed badly when applied to benzene. No obvious explanation was found for this unexpected feature, which makes it worth while to continue the investigations. The mean amplitudes of vibration were calculated. For perylene an account of the complete set of mean amplitudes is given for the first time.

Download Full-text