Ab initio calculation of vibrational frequencies of clusters in As x S1-x glass and Raman spectra

NASA Astrophysics Data System (ADS)

We have used the density functional theory (DFT) to calculate the vibrational frequencies from first principles by making clusters of atoms on a high speed computer. We have made the clusters, AsS4, As2S3, As3S2, As4S, AsS7, As2S6,As3S5,As4S4,As5S3,As6S2, As7S, L-As4S3, CS-As4S,CS-AsS4,ES-As2S6(L=linear zig-zag, CS=corner sharing, ES=edge sharing) and optimized the bond lengths and angles for the minimum energy. The number of computed values of the vibrational frequencies are consistent with 3N-3, where N is the number of atoms in a cluster. All of the computed values are tabulated and compared with those found in the Raman spectra of AsxS1-x (x=0.35-0.45) glasses. The experimentally found modes at 183, 221, 355, 371 cm-1 are consistent with those calculated for chain mode-As4S3, As3S2, As2S6, AsS7. In the net work glass the frequencies found are, 195, 206, 227, 351, 369, 371, 388 cm-1 which are consistent with those calculated for, As7S, As5S3, As7S, As6S2, As5S3, AsS7 and As4S. We have previously interpreted the Raman spectra of GeSI galass by this method ,V.R. Devi, et al, J. Non Cryst. Solids 351,489-494(2005).

Shrivastava, Keshav; Radhika Devi, V.; Abu Kassim, Hasan; Jalil, Ithnin Abdul; Yusof, Norhasliza

2007-03-01