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

TL;DR

This study uses first-principles molecular dynamics to investigate the static and dynamical properties of heavy water at ambient conditions, revealing structural details and diffusion behavior with high computational accuracy.

Contribution

It provides detailed first-principles simulation data on heavy water's properties, highlighting the effects of temperature and system size on structural and dynamical characteristics.

Findings

Density-functional theory accurately models water monomer and dimer properties.

Structural properties of bulk heavy water are more ordered than experimental data suggest.

Liquid-like diffusion in heavy water occurs only at 400 K in simulations.

Abstract

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.