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Molecular dynamics (MD) simulations have been performed for highly compressed fluid deuterium, nitrogen, and oxygen, in the density and temperature regime of shock-compression experiments, using density functional (DF) electronic structure techniques to describe the interatomic forces. The Hugoniots derived from the calculated equation-of-state for deuterium does not exhibit the large compression predicted by the recently reported laser-driven experiments. However, the Hugoniot derived for nitrogen and oxygen agree well with explosively-driven and gas-gun experiments. The nature of the fluid along the Hugoniot, as calculated with DF-MD, has been analyzed. All three species (D[sub 2], N[sub 2], and O[sub 2]) undergo a continuous transition from a molecular to a partially dissociated fluid containing a mixture of atoms and molecules. [ABSTRACT FROM AUTHOR]

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 Grüneisen parameters were deduced experimentally and where shock cooling was measured. [ABSTRACT FROM AUTHOR]