Ab initio Calculation of the geametry and vibrational frequencies of the isoelectronic tetrahedral species XCL ϵ4 and XS ϵ4(X = Ne-Ar) with extented and minimal basis sets

Abstract

Vibrational frequencies have been calculated with minimal and extended basis sets for the ions XCl ϵ 4 and XS ϵ 4 (X = Ne-Ar). For some of the highly charged ions very large bonding distances were calculated, and for some others with intermediate bonding distances a negative frequency for the T 2 stretching mode was predicted, indicating instability towards splitting off one ligand. For the chloride species the best fit was obtained with the extended basis sets. Extrapolation of the trends for the scaling factors was used to predict frequencies for the unknown ions NaCl 4 3−and SCl 4 2+. For the more covalently bonded sulphides the influence of basis sets is different than for the chlorides, and for the highly charged sulphides calculations with minimal basis sets appear to give better predictions of vibrational frequencies.