A theoretical study of the effect on the vibrational spectrum of the stepwise sulfur by selenium substitution in arsenic pentasulfide

This work deals with the theoretical investigation of the vibrational spectra of the As2S5-xSex (from x = 0 to x = 5 modes of glassy alloys) type compounds. Molecular geometries and vibrational spectra of all their conformers were calculated quantum chemically. Normal coordinate analysis was carried out for all these molecules. The results show the very characteristic positions of the central As-S and As-Se stretching frequencies. Besides, with increasing x all the normal modes become more and more characteristic, i.e. group frequencies. As expected, with increasing Se content the frequencies of the normal modes shifted to lower ones. (C) 2000 Elsevier Science B.V. All rights reserved.