MD simulations of laser-induced ultrashort shock waves in nickel

Abstract

The dynamics of ultrashort shock waves induced by femtosecond laser pulses were explored in nickel-glass and free-standing nickel films by molecular dynamics simulations. Ultrafast laser heating causes stress-confinement, which is characterized by formation of a strongly pressurized 100-nm-thick zone just below the surface of the film. For low-intensity laser pulses, only a single elastic shock wave was formed despite pressures several times greater than the experimental Hugoniot elastic limit. Because the material remains uniaxially compressed for < 50 ps, comparatively slow processes of dislocation formation are not activated. For high intensity laser pulses, the process of double wave breaking was observed with formation of split elastic and plastic shock waves. Presence of a trailing rarefaction wave acts to attenuate the plastic wave until it disappears. Agreement between the experimental and simulated Hugoniot was facilitated by a new EAM potential designed to simulate nickel in a wide range of pressures and temperatures.