Ab Initio van der Waals Interactions in Simulations of Water Alter Structure from Mainly Tetrahedral to High-Density-Like
Journal article, 2011

The structure of liquid water at ambient conditions is studied in ab initio molecular dynamics simulations in the NVE ensemble using van der Waals (vdW) density-functional theory, i.e., using the new exchange-correlation functionals optPBE-vdW and vdW-DF2, where the latter has softer nonlocal correlation terms. Inclusion of the more isotropic vdW interactions counteracts highly directional hydrogen bonds, which are enhanced by standard functionals. This brings about a softening of the microscopic structure of water, as seen from the broadening of angular distribution functions and, in particular, from the much lower and broader first peak in the oxygen-oxygen pair-correlation function (PCF) and loss of structure in the outer hydration shells. Inclusion of vdW interactions is shown to shift the balance of resulting structures from open tetrahedral to more close-packed. The resulting O-O PCF shows some resemblance with experiment for high-density water (Soper, A. K.; Ricci, M.A. Phys. Rev. Lett. 2000, 84, 2881), but not directly with experiment for ambient water. Considering the accuracy of the new functionals for interaction energies, we investigate whether the simulation protocol could cause the deviation. An O-O PCF consisting of a linear combination of 70% from vdW-DF2 and 30% from low-density liquid water, as extrapolated from experiments, reproduces near-quantitatively the experimental O-O PCF for ambient water. This suggests the possibility that the new functionals maybe reliable and that instead larger-scale simulations in the NPT ensemble, where the density is allowed to fluctuate in accordance with proposals for supercooled water, could resolve the apparent discrepancy with the measured PCF.

liquid water

stokes-einstein relation


generalized gradient approximation

functional theory

radial-distribution functions




hydrogen-bond network

ambient conditions



A. Mogelhoj

Stanford Synchrotron Radiation Laboratory

Technical University of Denmark (DTU)

A. K. Kelkkanen

Technical University of Denmark (DTU)

K. T. Wikfedt

Stockholm University

J. Schiotz

Technical University of Denmark (DTU)

J. J. Mortensen

Technical University of Denmark (DTU)

L. G. M. Pettersson

Stockholm University

Bengt Lundqvist

Chalmers, Applied Physics, Materials and Surface Theory

K. W. Jacobsen

Technical University of Denmark (DTU)

A. Nilsson

Stanford Synchrotron Radiation Laboratory

J. K. Norskov

Stanford Synchrotron Radiation Laboratory

Technical University of Denmark (DTU)

Stanford University

Journal of Physical Chemistry B

1520-6106 (ISSN) 1520-5207 (eISSN)

Vol. 115 48 14149-14160

Subject Categories

Physical Chemistry



More information

Latest update

3/6/2018 1