Boson peak in amorphous silicon: A numerical study
The low-frequency part of the phonon spectrum of a-Si is investigated for a microscopic model of this amorphous solid even for frequencies below 50 cm{minus}1. This requires system sizes up to 64000 atoms. The variation of a model parameter allows us to generate structures with different degrees of disorder. The vibrational properties are calculated in a harmonic approximation to the Stillinger-Weber potential. The less disordered of our models already show an enhancement of the low-frequency vibrational density of states g({omega}) (VDOS) compared to the crystal. For the more disordered structures additionally a peak in g({omega})/{omega}{sup 2} versus {omega} is observed. The deviation from the Debye {omega}{sup 2} behavior is caused by at least two effects: a shift of the crystalline transverse acoustic peak toward lower frequency and a broadening of the same. Consequently the occurrence of the boson peak in the Raman spectrum of a-Si can be explained already in the harmonic approximation (at least in part) by a complex of phenomena of the low-frequency VDOS.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40203603
- Journal Information:
- Physical Review B, Vol. 63, Issue 23; Other Information: DOI: 10.1103/PhysRevB.63.235204; Othernumber: PRBMDO000063000023235204000001; 047119PRB; PBD: 15 Jun 2001; ISSN 0163-1829
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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