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Toward Accurate Adsorption Energetics on Clay Surfaces

Zen, A; Roch, LM; Cox, SJ; Hu, XL; Sorella, S; Alfe, D; Michaelides, A; (2016) Toward Accurate Adsorption Energetics on Clay Surfaces. The Journal Of Physical Chemistry C , 120 (46) pp. 26402-26413. 10.1021/acs.jpcc.6b09559. Green open access

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Abstract

Clay minerals are ubiquitous in nature, and the manner in which they interact with their surroundings has important industrial and environmental implications. Consequently, a molecular-level understanding of the adsorption of molecules on clay surfaces is crucial. In this regard computer simulations play an important role, yet the accuracy of widely used empirical force fields (FF) and density functional theory (DFT) exchange-correlation functionals is often unclear in adsorption systems dominated by weak interactions. Herein we present results from quantum Monte Carlo (QMC) for water and methanol adsorption on the prototypical clay kaolinite. To the best of our knowledge, this is the first time QMC has been used to investigate adsorption at a complex, natural surface such as a clay. As well as being valuable in their own right, the QMC benchmarks obtained provide reference data against which the performance of cheaper DFT methods can be tested. Indeed using various DFT exchange-correlation functionals yields a very broad range of adsorption energies, and it is unclear a priori which evaluation is better. QMC reveals that in the systems considered here it is essential to account for van der Waals (vdW) dispersion forces since this alters both the absolute and relative adsorption energies of water and methanol. We show, via FF simulations, that incorrect relative energies can lead to significant changes in the interfacial densities of water and methanol solutions at the kaolinite interface. Despite the clear improvements offered by the vdW-corrected and the vdW-inclusive functionals, absolute adsorption energies are often overestimated, suggesting that the treatment of vdW forces in DFT is not yet a solved problem.

Type: Article
Title: Toward Accurate Adsorption Energetics on Clay Surfaces
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acs.jpcc.6b09559
Publisher version: http://doi.org/10.1021/acs.jpcc.6b09559
Language: English
Additional information: © 2016 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
Keywords: Science & Technology, Physical Sciences, Technology, Chemistry, Physical, Nanoscience & Nanotechnology, Materials Science, Multidisciplinary, Chemistry, Science & Technology - Other Topics, Materials Science, QUANTUM MONTE-CARLO, GENERALIZED GRADIENT APPROXIMATION, INITIO MOLECULAR-DYNAMICS, DENSITY-FUNCTIONAL THEORY, PARTICLE MESH EWALD, RIETVELD REFINEMENT, KAOLINITE STRUCTURE, CRYSTAL-STRUCTURE, IN-VITRO, WATER
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1528641
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