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Title: Benchmarking the performance of density functional theory and point charge force fields in their description of sI methane hydrate against diffusion Monte Carlo

High quality reference data from diffusion Monte Carlo calculations are presented for bulk sI methane hydrate, a complex crystal exhibiting both hydrogen-bond and dispersion dominated interactions. The performance of some commonly used exchange-correlation functionals and all-atom point charge force fields is evaluated. Our results show that none of the exchange-correlation functionals tested are sufficient to describe both the energetics and the structure of methane hydrate accurately, while the point charge force fields perform badly in their description of the cohesive energy but fair well for the dissociation energetics. By comparing to ice I{sub h}, we show that a good prediction of the volume and cohesive energies for the hydrate relies primarily on an accurate description of the hydrogen bonded water framework, but that to correctly predict stability of the hydrate with respect to dissociation to ice I{sub h} and methane gas, accuracy in the water-methane interaction is also required. Our results highlight the difficulty that density functional theory faces in describing both the hydrogen bonded water framework and the dispersion bound methane.
Authors:
;  [1] ;  [2] ;  [3] ;  [2] ;  [1] ;  [2]
  1. Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom)
  2. (United Kingdom)
  3. Department of Earth Sciences, University College London Gower Street, London WC1E 6BT (United Kingdom)
Publication Date:
OSTI Identifier:
22252965
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 17; Other Information: (c) 2014 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; CRYSTALS; DENSITY FUNCTIONAL METHOD; DIFFUSION; DISPERSIONS; DISSOCIATION; HYDROGEN; INTERACTIONS; METHANE; MONTE CARLO METHOD; POINT CHARGE; WATER