Thermodynamics of dense fluid nitrogen by molecular dynamics

We present an extensive set of molecular dynamics results for the thermodynamics of dense fluid N2. The density and temperature regime is 1.3 g/cm3< or approx. =rho< or approx. =2.3 g/cm3 and 500 K< or approx. =T< or approx. =12 000 K. These data are then analyzed to study the effects of internal degrees of freedom on the N2 equation of state. Most importantly, we demonstrate the existence of an effective spherical potential that models very accurately (to 1.5% or better in pressure and energy) the true equation of state for the anisotropic N2 potential. We discuss the relation of this effective potential to the median average over angles and other averaging methods, including the arithmetic mean