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).