Sound velocity, equation of state, temperature and melting of LiF single crystals under shock compression

Internal particle velocity history measurements are performed on [100] LiF single crystals under plate impact to 2-152 GPa, to investigate the Gruneisen equation of state and shock-induced melting. Hugoniot and sound velocities of LiF are obtained via the Lagrangian analysis. The drop in the longitudinal sound velocity to bulk sound velocity between 134 and 152 GPa, suggests that shock-induced melting initiates at 134-152 GPa. The Gruneisen parameter as a function of shock-state density is determined. Given high-pressure Gruneisen parameters, shock temperature and melting curve of B1 phase LiF are calculated, and consistent with previous molecular dynamics and ab initio calculations, as well as diamond-anvil cell and shock wave measurements. Our calculation suggests that shock-induced melting initiates at 142 GPa, in agreement with our sound velocity measurements. (C) 2015 AIP Publishing LLC.