K. Ramaswamy

Molecular force field for interhalogen compounds: IF5, IOF5 and IF7

Abstract The potential energy constants of IF 5 , IOF 5 and IF 7 have been calculated using a Urey-Bradley force field taking into account the presence of the lone pair of electrons. The mean vibrational amplitudes have been obtained from the vibrational spectral data and Coriolis coupling constants and rotational distortion constants have also been evaluated.

Molecular force field for seleninyl fluoride and selenonyl fluoride

Abstract The potential energy constants of seleninyl fluoride and selenonyl fluoride were calculated using a Urey-Bradley force field and taking into account the presence of the lone pair of electrons. The value for the Se-F stretching force constant was found to be 3.6696 mdyn A −1 for SeOF 2 and 4.5790 mdyn A −1 for SeO 2 F 2 . Mean vibrational amplitudes, Coriolis constants and the rotational distortion constants were also evaluated.

On the evaluation of the force field of halogenated ethylenes

Abstract An attempt was made to calculate the force fields of ethylene and halogenated ethylenes using Redingtons approach. The mean vibrational amplitude, Coriolis coupling constants and inertia defects were also calculated. It was found that a reasonably good force field could be generated using Redingtons approach for ethylene-type molecules.

Molecular force fields for interhalogen compounds: II. Chlorine and bromine pentafluorides

Abstract The potential energy constants of chlorine and bromine pentafluorides were calculated using a ubff taking into account the presence of the lone pair of elec- trons. The mean vibrational amplitudes were obtained from the vibrational spectral data. The Coriolis coupling constants and the rotational distortion con- stants were also evaluated.

Green's function analysis of SF6, and related molecules

Abstract The isotopic rules for various substitutions of XY6 octahedral molecules were formulated using the Greens function analysis. The molecular constants of SF6 were determined. Some of the vibrational frequencies of the substituted molecules like SeF6, TeF6, SF5Cl, SF5CF3 and SF5Br were predict edusing the frequencies of the parent molecule SF6. The changes in the force constant were also calculated.

An empirical force field for ethylenes: application to C2X4 and CH2CX2 (X = halogen) type molecules

Abstract The empirical force field previously proposed by the authors was modified and applied to some halogen substituted ethylenes. ∂ r ∂λ values were determined for these molecules and used to calculate the changes in the electronegativity difference of the CX bonds corresponding to the changes in configuration.

Molecular constants of C3X2 (X = O, S) and C4H4 molecules

Abstract The potential energy constants and mean amplitudes of vibration for C 3 O 2 and C 3 S 2 and the molecular constants of C 4 H 4 have been evaluated using the method of ‘characteristic set of valence coordinates’. It is shown that the conventional set of symmetry coordinates lead to abnormally large values for the constants. Hence a different set of symmetry coordinates was chosen which gives a reliable set of force constants. It is also shown that the second set of symmetry coordinates provides better agreement with the experimental data for both mean amplitudes and rotational distortion constants of butatriene. The various large values for the C 3 X 2 molecules were attributed to the high degree of delocalisation in these systems.

Green's function analysis of carbon trioxide

Abstract Potential energy constants of CO 3 were calculated by the Greens function procedure, using the available isotopic data. From the isotopic rules obtained, the frequencies of various isotopic species were calculated and compared with the observed values. The mean amplitudes of vibration were also evaluated.

Molecular force field for sulphuryl bromide fluoride and sulphuryl chloride fluoride

Abstract A normal coordinate analysis was carried out for SO2BrF and SO2ClF using the Urey-Bradley type of force field. Mean vibrational amplitudes were also evaluated.

Electrooptical parameters and polar tensors of some XY3 type molecules

Abstract The electrooptical parameters of some XY 3 (X = P, N; Y = F, H) pyramidal type molecules are calculated using the transformation matrix obtained by the virial theorem approach. The sign combinations of the various modes of vibration have been predicted by calculating the equilibrium dipole moment of the molecules. The results using this method are at variance with those of other methods of choosing the correct signs of the dipole derivatives. Polar tensors for the constituent atoms of the molecules for the preferred sign combination are determined and the intensity sum rule verified.