1999/11/16 by Serge Nakhmanson, S. M. Nakhmanson, D. A. Drabold · 1 citation
Materials Science · Physics and Astronomy · #Phase-change materials and chalcogenides #Quantum and electron transport phenomena #Spectroscopy and Quantum Chemical Studies #cond-mat.dis-nn #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.61.5376
5 pages with 2 ps figures, submitted to PRB
arxiv created 1999/11/16 · openalex publication_date 2000/02/15 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Using empirical potential molecular dynamics we compute dynamical matrix eigenvalues and eigenvectors for a 4096 atom model of amorphous silicon and a set of models with voids of different sizes based on it. This information is then employed to study the localization properties of the low-energy vibrational states, calculate the specific heat C(T), and examine the low-temperature properties of our models usually attributed to the presence of tunneling states in amorphous silicon. The results of our calculations for C(T) and ``excess specific-heat bulge'' in the C(T)/T3 vs T graph for voidless a\ensuremath-Si appear to be in good agreement with experiment; moreover, our investigation shows that the presence of localized low-energy excitations in the vibrational spectrum of our models with voids strongly manifests itself as a sharp peak in C(T)/T3 dependence at T<3 K. To our knowledge this is the first numerical simulation that provides adequate agreement with experiment for the very-low-temperature properties of specific heat in disordered systems within the limits of harmonic approximation.