Vibrational behaviour of a realistic amorphous-silicon model

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 $\Gamma$ of the best-fit DHO to the longitudinal dynamical structure factor scales approximately as $k^2$ for wavevectors $k\lesssim 0.55{\text{A˚}}^{-1}$, which is above the Ioffe-Regel crossover frequency separating the propagating and diffusing regimes, occurring at $k=0.38\pm 0.03{\text{A˚}}^{-1}$. Using the DHO function as a fitting function for the transverse dynamical structure factor (without theoretical justification), gives a dependence of $\Gamma \propto k^{\alpha }$ with $\alpha \sim 2.5$ for wavevectors $k\lesssim 0.7{\text{A˚}}^{-1}$. There was no evidence for $\Gamma \propto k^4$ behaviour for either polarization.

18 pages, 11 figures, uses Elsevier file 'elsart.cls', submitted to J. Non-Cryst. Solids

References in corpus (1)

• Universal Features of Terahertz Absorption in Disordered Materials