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**Harvard**

Mogelhoj, A., Kelkkanen, A., Wikfedt, K., Schiotz, J., Mortensen, J., Pettersson, L., Lundqvist, B., Jacobsen, K., Nilsson, A. och Norskov, J. (2011) *Ab Initio van der Waals Interactions in Simulations of Water Alter Structure from Mainly Tetrahedral to High-Density-Like*.

** BibTeX **

@article{

Mogelhoj2011,

author={Mogelhoj, A. and Kelkkanen, A. K. and Wikfedt, K. T. and Schiotz, J. and Mortensen, J. J. and Pettersson, L. G. M. and Lundqvist, Bengt I. and Jacobsen, K. W. and Nilsson, A. and Norskov, J. K.},

title={Ab Initio van der Waals Interactions in Simulations of Water Alter Structure from Mainly Tetrahedral to High-Density-Like},

journal={Journal of Physical Chemistry B},

issn={1520-6106},

volume={115},

issue={48},

pages={14149-14160},

abstract={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.},

year={2011},

keywords={x-ray-scattering, generalized gradient approximation, molecular-dynamics, simulation, radial-distribution functions, stokes-einstein relation, hydrogen-bond network, liquid water, functional theory, supercooled, water, ambient conditions},

}

** RefWorks **

RT Journal Article

SR Electronic

ID 151593

A1 Mogelhoj, A.

A1 Kelkkanen, A. K.

A1 Wikfedt, K. T.

A1 Schiotz, J.

A1 Mortensen, J. J.

A1 Pettersson, L. G. M.

A1 Lundqvist, Bengt I.

A1 Jacobsen, K. W.

A1 Nilsson, A.

A1 Norskov, J. K.

T1 Ab Initio van der Waals Interactions in Simulations of Water Alter Structure from Mainly Tetrahedral to High-Density-Like

YR 2011

JF Journal of Physical Chemistry B

SN 1520-6106

VO 115

IS 48

SP 14149

OP 14160

AB 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.

LA eng

DO 10.1021/jp2040345

LK http://dx.doi.org/10.1021/jp2040345

OL 30