Molecular-dynamics simulation of thermoelastic waves in a solid induced by a strong impulse energy

Abstract

A molecular-dynamics investigation of thermoelastic waves in a solid at various pressures and temperatures has been studied. The numerical experiments were performed on a two-dimensional ^111& plane consisting of fcc lattice particles having the Lennard-Jones ~12-6! interaction potentials. Three types of impulse energy, including thermal, kinetic, and superposition of thermal and kinetic energies, were employed to investigate the origins and characteristics of the generated waves. According to their propagating speeds, three waves, namely, W1 , W2 , and W3 , were observed if a kinetic impulse energy was imposed. But only the W1 and W3 waves were detectable if the applied energy was thermal. The W1 wave, accompanied by a strong compressive stress wave, is the first sound wave and caused by sudden expansion as the impulse energy applied. Due to coupling of thermal and elastic energies, it is a nonequilibrium thermoelastic wave. The W2 wave was initiated by strong velocity disturbance in the longitudinal direction. If induced by a thermal impulse energy, the W3 wave is the so-called second sound. The monotonically decreasing of the second sound speed with increasing temperature is also verified.