A comparison of amplitudes and shrinkage corrections for C 6Cl 3(NO 2) 3 calculated using conventional and new procedures

Abstract

A harmonic force field for C 6Cl 3(NO 2) 3 has been estimated, and the calculated and experimental vibrational frequencies are compared. The vibrational amplitudes and shrinkage corrections have been calculated using 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 technique (2) are substantially (an order of magnitude) smaller than those 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.