Proton Quantum Effects in High Pressure Hydrogen

We present a combined path integral molecular dynamics density functional study of high density hydrogen at T =50 K and r_s=1.5 (corresponding to a pressure of about 1.5 Mbar). The effects of the proton quantum character are included beyond the usual harmonic approximations in a finite-temperature ab initio calculation. The ground state structure in the corresponding classical system remains stable but is significantly broadened by quantum dispersion effects. Simple quasiclassical models are shown to fail in the description of these dispersion effects due to strong correlations between the protons.