Quantum Molecular Dynamics: a New Algorithm for Linear and Nonlinear Electron Transport in Disordered Materials

Abstract

Quantum molecular dynamics (QMD) simulations pro vide the real-time dynamics of electrons and ions through numerical solutions of the time-dependent Schrödinger and Newton equations, respectively. With this technique it is possible to go beyond the structural aspects to study electron dynamics, including linear and nonlinear electron transport, in materials at finite tem peratures. The solution of the time-dependent Schrö dinger equation for the electron wave function is ob tained by a spectral method, which for bulk systems is implemented with discrete fast Fourier (FFT) transforms. For systems with broken symmetry due to surfaces or interfaces, the spectral method combines the solution of a tridiagonal set of equations with FFT. Using QMD simulations we have investigated the localization be havior and the mobility of excess electrons at finite tem peratures in highly disordered systems such as a dense helium gas and amorphous silicon. Future QMD simula tions for many electrons within the framework of time- dependent density functional theory and implementation of molecular dynamics on massively parallel architec tures are discussed.