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

Abstract

Articles you may be interested inPhotoelectron spectroscopy and density functional theory studies on the uridine homodimer radical anions J. Chem. Phys. 137, 205101 (2012) 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 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 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.

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“…33 Here, we report a substantial set of benchmarks from the quantum Monte Carlo (QMC) technique [34][35][36] for thermally disordered methane-water clusters containing up to 20 water monomers. Using these benchmarks together with other recent QMC results, 37,38 we assess the accuracy of the second-order Møller-Plesset (MP2) technique for both methane-water clusters and the methane hydrate crystal. a) Author to whom correspondence should be addressed.…”

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“…Diffusion quantum Monte Carlo (DMC) provides accurate energies for vdW systems. [40][41][42][43][44][45][46] DMC is also able to produce an accurate description of systems where many-body interactions play a key role. 47,48 In general, QMC based methods are faster than the most accurate post-Hartree-Fock schemes for large number of particles N. The computational cost of QMC methods scales usually as N 3 -N 4 depending on the method.…”