• Ma, Pui-Wai
• Duffy, Dorothy
• Darkins, Robert
• Murphy, St

Abstract

Radiation can drive the electrons in a material out of thermal equilibrium with the nuclei, producing hot, transient electronic states that modify the interatomic potential energy surface. We present a rigorous formulation of two-temperature molecular dynamics that can accommodate these electronic effects in the form of electronic-temperature-dependent force fields. Such a force field is presented for silicon, which has been constructed to reproduce the ab initio-derived thermodynamics of the diamond phase for electronic temperatures up to <br/>2.5eV, as well as the structural dynamics observed experimentally under nonequilibrium conditions in the femtosecond regime. This includes nonthermal melting on a subpicosecond timescale to a liquidlike state for electronic temperatures above∼1eV. The methods presented in this paper lay a rigorous foundation for the large-scale atomistic modeling of electronically driven structural dynamics with potential applications spanning the entire domain of radiation damage.

Topics

• impedance spectroscopy
• surface
• phase
• molecular dynamics
• Silicon