PROTON-PROTON PAIR DISTRIBUTION IN DENSE FLUID HYDROGEN

Recent experiments on hydrogen at very high pressures have stimulated new quantum statistical studies of this simplest Coulomb system since a transition from nonconducting to metallic behavior occurs at Mbar pr essures which is forced by drastic changes of the electronic and struc tural properties in the molecular system with increasing density. The variation of the thermodynamic and structural properties as a function of the density and temperature can be studied within molecular dynami cs and Monte Carlo simulations as well as within analytical approaches such as integral equation techniques. In the region where hydrogen mo lecules still dominate the physical behavior, the proton-proton pair d istribution function is determined both from a modified hypernetted ch ain approximation which starts with effective intermolecular and inter atomic potentials in the neutral system, and a wave-packet molecular d ynamics simulation with the Coulomb interaction between protons and el ectrons as the basic interaction. Comparison of both complementary app roaches gives hints for the validity region of the chemical picture as well as for the accuracy of computer simulations.