Ultra Fast Heat Transport Analysis by Modified Molecular Dynamics Applying Non-Fourier Law to Electron Heat Conduction

摘要

Heat transport mechanism of femtosecond laser ablation is investigated by using modified molecular dynamics (MMD). In order to describe both electron heat conduction and thermal non-equilibrium between electron and atom, MMD couples conventional molecular dynamics with two temperature model, in which non-Fourier law is applied to electron heat flux term. Trough in-silico experiment, it is found that the effect of non-Fourier law remains in electron thermal behavior up to several hundreds femtosecond, while thermal behavior of atoms is not affected by application of non-Fourier law to electron heat flux. Thermal relaxation time between electron and atom is several tens picosecond order. Dominant heat transport mechanism consists of the electron heat conduction before generation of thermal shock wave, while, after that, it consists of both electron heat conduction and thermal shock wave. In addition, it is confirmed that large velocity gradient resulting from drastic thermal expansion is one of origins of phase change.