Water orientation and hydrogen-bond structure at the fluorite/water interface

Water in contact with mineral interfaces is important for a variety of different processes. Here, we present a combined theoretical/experimental study which provides a quantitative, molecular-level understanding of the ubiquitous and important CaF2/water interface. Our results show that, at low pH,...

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Main Authors:	Khatib, Rémi, Backus, Ellen H. G., Bonn, Mischa, Perez-Haro, María-José, Gaigeot, Marie-Pierre, Sulpizi, Marialore
Format:	Online
Language:	English
Published:	Nature Publishing Group 2016
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4828669/

id	pubmed-4828669
recordtype	oai_dc
spelling	pubmed-48286692016-04-19 Water orientation and hydrogen-bond structure at the fluorite/water interface Khatib, Rémi Backus, Ellen H. G. Bonn, Mischa Perez-Haro, María-José Gaigeot, Marie-Pierre Sulpizi, Marialore Article Water in contact with mineral interfaces is important for a variety of different processes. Here, we present a combined theoretical/experimental study which provides a quantitative, molecular-level understanding of the ubiquitous and important CaF2/water interface. Our results show that, at low pH, the surface is positively charged, causing a substantial degree of water ordering. The surface charge originates primarily from the dissolution of fluoride ions, rather than from adsorption of protons to the surface. At high pH we observe the presence of Ca-OH species pointing into the water. These OH groups interact remarkably weakly with the surrounding water, and are responsible for the “free OH” signature in the VSFG spectrum, which can be explained from local electronic structure effects. The quantification of the surface termination, near-surface ion distribution and water arrangement is enabled by a combination of advanced phase-resolved Vibrational Sum Frequency Generation spectra of CaF2/water interfaces and state-of-the-art ab initio molecular dynamics simulations which include electronic structure effects. Nature Publishing Group 2016-04-12 /pmc/articles/PMC4828669/ /pubmed/27068326 http://dx.doi.org/10.1038/srep24287 Text en Copyright © 2016, Macmillan Publishers Limited http://creativecommons.org/licenses/by/4.0/ This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Khatib, Rémi Backus, Ellen H. G. Bonn, Mischa Perez-Haro, María-José Gaigeot, Marie-Pierre Sulpizi, Marialore
spellingShingle	Khatib, Rémi Backus, Ellen H. G. Bonn, Mischa Perez-Haro, María-José Gaigeot, Marie-Pierre Sulpizi, Marialore Water orientation and hydrogen-bond structure at the fluorite/water interface
author_facet	Khatib, Rémi Backus, Ellen H. G. Bonn, Mischa Perez-Haro, María-José Gaigeot, Marie-Pierre Sulpizi, Marialore
author_sort	Khatib, Rémi
title	Water orientation and hydrogen-bond structure at the fluorite/water interface
title_short	Water orientation and hydrogen-bond structure at the fluorite/water interface
title_full	Water orientation and hydrogen-bond structure at the fluorite/water interface
title_fullStr	Water orientation and hydrogen-bond structure at the fluorite/water interface
title_full_unstemmed	Water orientation and hydrogen-bond structure at the fluorite/water interface
title_sort	water orientation and hydrogen-bond structure at the fluorite/water interface
description	Water in contact with mineral interfaces is important for a variety of different processes. Here, we present a combined theoretical/experimental study which provides a quantitative, molecular-level understanding of the ubiquitous and important CaF2/water interface. Our results show that, at low pH, the surface is positively charged, causing a substantial degree of water ordering. The surface charge originates primarily from the dissolution of fluoride ions, rather than from adsorption of protons to the surface. At high pH we observe the presence of Ca-OH species pointing into the water. These OH groups interact remarkably weakly with the surrounding water, and are responsible for the “free OH” signature in the VSFG spectrum, which can be explained from local electronic structure effects. The quantification of the surface termination, near-surface ion distribution and water arrangement is enabled by a combination of advanced phase-resolved Vibrational Sum Frequency Generation spectra of CaF2/water interfaces and state-of-the-art ab initio molecular dynamics simulations which include electronic structure effects.
publisher	Nature Publishing Group
publishDate	2016
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4828669/
_version_	1613565085116006400

Water orientation and hydrogen-bond structure at the fluorite/water interface

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