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Hydrogen transfer and hydration properties of HnPO43-n (n=0-3) in water studied by first principles molecular dynamics simulations

Tang, E; Di Tommaso, D; de Leeuw, NH; (2009) Hydrogen transfer and hydration properties of HnPO43-n (n=0-3) in water studied by first principles molecular dynamics simulations. J CHEM PHYS , 130 (23) , Article 234502. 10.1063/1.3143952.

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Abstract

Density functional theory Perdew-Burke-Ernzerhof [Perdew et al., Phys. Rev. Lett. 77, 3865 (1996)] molecular dynamics simulations of aqueous solutions of orthophosphate species HnPO43-n (n=0-3) provide new insights into hydrogen transfer and intermolecular and hydration properties of these important aqueous species. Extensive Car-Parrinello molecular dynamics simulations of the orthophosphate ion PO43-, of the hydrogen phosphate anions, HPO42- and H2PO4-, and of the orthophosphoric acid, H3PO4, in explicit water show that the process of proton transfer from HnPO43-n to the surrounding water molecules is very fast, less than 1 ps, and indicate that the dehydrogenation occurs through a concerted proton hopping mechanism, which involves HnPO43-n and three water molecules. Analysis of the intermolecular HnPO43-n-water structure shows that the PO43- anions have a significant effect on the H-bonding network of bulk water and the presence of P-O- moieties induce the formation of new types of H-H interactions around this orthophosphate. Calculated probability distributions of the coordination numbers of the first hydration shell of PO43-, HPO42-, and H2PO4- show that these phosphate species display a flexible first coordination shell (between 7 and 13 water molecules) and that the flexibility increases on going from PO43- to H2PO4-. The strength and number of hydrogen bonds of PO43-, HPO42-, and H2PO4- are determined through a detailed analysis of the structural correlation functions. In particular, the H-bond interactions between the oxygen atoms of the phosphates and the surrounding water molecules, which decrease on going from PO43- to the hydrogenated H2PO4- species, explain the diminished effect on the structure of water with the increasing hydrogenation of the orthophosphate anions.

Type:Article
Title:Hydrogen transfer and hydration properties of HnPO43-n (n=0-3) in water studied by first principles molecular dynamics simulations
DOI:10.1063/1.3143952
Keywords:ab initio calculations, chemical exchanges, density functional theory, hydrogen bonds, hydrogen compounds, hydrogenation, intermolecular mechanics, liquid theory, molecular dynamics method, solvation, water, DENSITY-FUNCTIONAL THEORY, AB-INITIO, PHOSPHATE-GLASSES, AQUEOUS-SOLUTION, CAR-PARRINELLO, LIQUID WATER, SOLVATION, ACCURACY, RAMAN, IONS
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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