  The static and dynamical properties of heavy water have been studied at
ambient conditions with extensive Car-Parrinello molecular-dynamics simulations
in 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 and
binding energy of the water monomer and dimer. On the other hand, the
structural and dynamical properties of the bulk liquid show a clear enhancement
of the local structure compared to experimental results; a distinctive
transition to liquid-like diffusion occurs in the simulations only at the
elevated temperature of 400 K. Extensive runs of up to 50 picoseconds are
needed to obtain well-converged thermal averages; the use of ultrasoft or
norm-conserving pseudopotentials and the larger plane-wave sets associated with
the latter choice had, as expected, only negligible effects on the final
result. Finite-size effects in the liquid state are found to be mostly
negligible for systems as small as 32 molecules per unit cell.
