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–As3) 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 Å and from 4.5 to 7.5 Å 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 Å (for g-As2S3) and 6.2 Å (for g-As22S78).