Ionic adsorption on the brucite (0001) surface: A periodic electrostatic embedded cluster method study

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Abstract

Density functional theory at the GGA level is employed within the periodic electrostatic embedded cluster method (PEECM) to model the brucite (0001) surface. Three representative studies are then used to demonstrate the reliability of the PEECM for the description of the interactions of various ionic species with the layered Mg(OH)2 structure, and its performance is compared with periodic DFT, an approach known to be challenging for the adsorption of charged species. The adsorption energies of a series of s block cations, including Sr2+ and Cs+ which are known to coexist with brucite in nuclear waste storage ponds, are well described by the embedded cluster model provided basis sets of triple-zeta quality are employed for the adsorbates. The substitution energies of Ca2+ and Sr2+ into brucite obtained with the PEECM are very similar to periodic DFT results, and comparison of the approaches indicates that two brucite layers in the quantum mechanical part of the PEECM are sufficient to describe the substitution. Finally, detailed comparison of the periodic and PEECM DFT approaches to the energetic and geometric properties of differently coordinated Sr[(OH)2(H2O)4] complexes on brucite shows excellent agreement in adsorption energies, Sr–O distances and bond critical point electron densities (obtained via the Quantum Theory of Atoms in Molecules), demonstrating that the PEECM can be a useful alternative to periodic DFT in these situations.

Bibliographical metadata

Original languageEnglish
Article number204708
JournalThe Journal of Chemical Physics
Volume145
DOIs
StatePublished - 30 Nov 2016