Local-spin-density-approximation molecular-dynamics simulations of dense deuterium

Local-spin-density-approximation molecular-dynamics simulations of deuterium in the dissociating regime are presented, with a particular emphasis on the molecular phase of two isochores corresponding for deuterium to V=6 cm³/mole, ρ=0.670 g/cm³ and V=4 cm³/mole, ρ=1 g/cm³. It is shown that the transition from the molecular regime, well described by the local-spin-density-approximation functional, to the dissociated regime where previous local-density-approximation results are recovered, comes with a negative curvature δP/δT<0 in the isochore. We show that this effect is not enough to explain the large compressibility measured in the laser experiments [L. B. DaSilva et al., Phys. Rev. Lett. 78, 483 (1997); G. W. Collins et al., Science 281, 1178 (1998); P. Celliers et al., Phys. Rev. Lett. 84, 5564 (2000)].