Density functional calculation of the Hugoniot of shocked liquid nitrogen

We performed molecular dynamics simulations to obtain the internal energy and pressure of shock-compressed fluid nitrogen. Our calculations were performed using the generalized gradient approximation (GGA) in density functional theory. From this equation of state, we derived the principal and second shock Hugoniots in the density region probed by gas-gun experiments. While the single-shock Hugoniot derived from this equation of state agrees well with gas-gun experiments; in contrast, the second-shock Hugoniots show discrepancies with the experimental measurements. This is particularly the case in the region where negative Gruneisen parameters were deduced experimentally and where shock cooling was measured.