Vibrational anharmonicity in octahedral XY 6 molecules

Formulae for the vibrational anharmonic coefficients Xrs, Grs, Trs and Srs have been derived for the case of octahedral XY 6 spherical top molecules. The vibrational contact transformation is first presented in general form and then worked out for the specific constants of the XY 6 model. The complete set of results is given in tabular form suitable for automatic computation and the important coefficients relating to bond stretching anharmonicity (rs = 11, 12, 13, 22, 23 and 33) are also quoted as algebraic expressions. Formulae for vibration-rotation coefficients of q 2 J 2-type operators are also given as an Appendix.