Boson peak of AsxS1-x glasses and theoretical calculations of low frequencies clusters vibrations

The results of comparison of spectral position of the LF bands of g-As2S3 and g-As22S78 with theoretical calculations of vibrational spectra of different clusters (As2S4, As2S5, As2S6, AsS3-As-3) in the LF region (10-85 cm(-1)) are given. The torsion type vibrations of the small chain-like clusters are located in the same spectral region as Boson peak of As-S glasses system. They can make several contributions to the LF spectrum. The cluster lengths by weight distribution functions f(L)*L are from 5.5 to 10.1 Angstrom and from 4.5 to 7.5 Angstrom for g-As2S3 and g-As22S78, respectively. The lognormal fittings of the f(L)*L functions give the most probably values about the 7.6 Angstrom (for g-As2S3) and 6.2 Angstrom (for g-As22S78).(C) 2003 Elsevier Ltd. All rights reserved.