Vibrational behaviour of a realistic amorphous-silicon model
arXiv:cond-mat/0701170 · doi:10.1016/j.jnoncrysol.2007.02.039
Abstract
The vibrational properties of a high-quality realistic model of amorphous silicon are examined. The longitudinal and transverse dynamical structure factors are calculated, and fitted to a damped harmonic oscillator (DHO) function. The width $Î$ of the best-fit DHO to the longitudinal dynamical structure factor scales approximately as $k^{2}$ for wavevectors $k\lesssim0.55\textrmà ^{-1}$, which is above the Ioffe-Regel crossover frequency separating the propagating and diffusing regimes, occurring at $k=0.38\pm0.03\textrmà ^{-1}$. Using the DHO function as a fitting function for the transverse dynamical structure factor (without theoretical justification), gives a dependence of $Î\propto k^α$ with $α\sim2.5$ for wavevectors $k\lesssim0.7\textrmà ^{-1}$. There was no evidence for $Î\propto k^{4}$ behaviour for either polarization.
18 pages, 11 figures, uses Elsevier file 'elsart.cls', submitted to J. Non-Cryst. Solids