Contribution of electronic excitation of the structural evolution of ultrafast laser-irradiated tungsten nano films

Murphy, Samuel and Giret, Yvelin and Daraszewicz, Szymon and Lim, Anthony and Shluger, Alexander and Tanimura, Katsumi and Duffy, Dorothy (2016) Contribution of electronic excitation of the structural evolution of ultrafast laser-irradiated tungsten nano films. Physical Review B: Condensed Matter and Materials Physics, 93. ISSN 1098-0121

Abstract

The redistribution of the electron density in a material during laser irradiation can have a significant impact on its structural dynamics. This electronic excitation can be incorporated into two temperature molecular dynamics (2T-MD) simulations through the use of electronic temperature dependent potentials. Here, we study the structural dynamics of laser irradiated tungsten nanofilms using 2T-MD simulations with an electronic temperature dependent potential and compare the results to equivalent simulations that employ a ground-state interatomic potential. Electronic excitation leads to an expansion of the crystal and a decrease in the melting point of tungsten. During laser irradiation these factors ensure that the threshold fluences to the different melting regimes are reduced. Furthermore, both heterogenous and homogeneous melting are predicted to occur more rapidly due to excitation and oscillations in the film thickness will be accentuated.