A COMPARISON OF AMPLITUDES AND SHRINKAGE CORRECTIONS FOR C6CL3(NO2)(3) CALCULATED USING CONVENTIONAL AND NEW PROCEDURES

A harmonic force field for C6Cl3(NO2)(3) has been estimated, and the c alculated and experimental vibrational frequencies are compared. The v ibrational amplitudes and shrinkage corrections have been calculated u sing the conventional technique based on normal coordinate analysis (1 ) and the new technique of taking into consideration non-linear terms in the transformation between the Cartesian and internal coordinates ( 2). The shrinkage corrections for bonded distances calculated using te chnique (2) are substantially (an order of magnitude) smaller than tho se calculated with the conventional procedure (1). The opposite effect is observed for non-bonded distances depending on internal rotations, which is more consistent with the physical sense of the influence of vibrational motions on the molecular structure.