Orbital Valence,Urey-Bradley and Approximate General Valence Force Fields and Vibrational Mean Amplitudes of Some Spherical Top M(CH3)4 Type Molecular Model (M=C,Si, Ge,Sn and Pb)

The intramolecular force fields of tetramethylcarbon, tetramethylsilane, tetramethylgermanium, tetramethyltin and tetramethyllead have been examined using OVFF, UBFF and GVFf potential functions under the approximation of ‘point-mass’ for methyl group. Approximate force fields for the (2x2)F₂ species of each molecule have been examined using L₁₂=O, L₂₁=O and P.E.D., methods. Transferability of OVFF into GVFF has also been observed. An analysis of the Coriolis coupling constants has been presented in the light of the force fields of the molecules. Vibrational mean amplitudes for bonded and non-bonded distances have been reported and analysed. The Bastiansen-Morino shrinkage effedt has been evaluated. The results have been discussed in the light of the relative behaviour of the molecules.