Static and dynamical properties of heavy water at ambient conditions from first-principles molecular dynamics

摘要

The static and dynamical properties of heavy water have been studied atambient conditions with extensive Car-Parrinello molecular-dynamics simulationsin the canonical ensemble, with temperatures ranging between 325 K and 400 K.Density-functional theory, paired with a modern exchange-correlation functional(PBE), provides an excellent agreement for the structural properties andbinding energy of the water monomer and dimer. On the other hand, thestructural and dynamical properties of the bulk liquid show a clear enhancementof the local structure compared to experimental results; a distinctivetransition to liquid-like diffusion occurs in the simulations only at theelevated temperature of 400 K. Extensive runs of up to 50 picoseconds areneeded to obtain well-converged thermal averages; the use of ultrasoft ornorm-conserving pseudopotentials and the larger plane-wave sets associated withthe latter choice had, as expected, only negligible effects on the finalresult. Finite-size effects in the liquid state are found to be mostlynegligible for systems as small as 32 molecules per unit cell.