AB-INITIO QUANTUM-MECHANICAL CALCULATIONS OF ENERGY, GEOMETRY, VIBRATIONAL FREQUENCIES AND IR INTENSITIES OF TETRAPHOSPHORUS TETRASULFIDE, ALPHA-P4S4(D2D), AND VIBRATIONAL ANALYSIS OF AS4S4 AND AS4SE4

Geometry, vibrational frequencies and IR intensities are calculated fo r alpha-P4S4 by scaled quantum mechanical calculations at the 6-31G/S CF and STO-3G/SCF levels. For both basis sets the frequencies are sca led with factors close to or equal to those found for P4S3, and based on these results a revised assignment is proposed. The alpha-P4S4 forc e field is transferred to the isostructural As4S4 and As4Se4 molecules and rescaled, and based on a good fit to experimental frequencies a n ew assignment is also proposed for these compounds.