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

Abstract

Density functional theory (DFT) at the generalised gradient approximation 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) 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 Sr and Cs which are known to coexist with brucite in nuclear waste storage ponds, are well described by the embedded cluster model, provided that basis sets of triple-zeta quality are employed for the adsorbates. The substitution energies of Ca and Sr 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, a detailed comparison of the periodic and PEECM DFT approaches to the energetic and geometric properties of differently coordinated Sr[(OH)(HO)] complexes on brucite shows an 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.

Oxygen Vacancy Formation and Water Adsorption on Reduced AnO2{111}, {110}, and {100} Surfaces (An = U, Pu): A Computational Study

“…We end with a note about the PEECM. We have now used the approach to study not only bulk and surface AnO 2 chemistry but also the brucite (0001) surface and the effects of the long-range environment on the quantum theory of atoms-in-molecules properties of molecular actinide compounds . This variety suggests a very useful transferability of the approach across a range of problems.…”

Surface Speciation of Brucite Dissolution in Aqueous Mineral Carbonation: Insights from Density-Functional Theory Simulations

“…A concern may be raised that the interaction energies upon involving adsorbing charged species will be dependent on the system’s charge. To alleviate such effects, a relatively large vacuum space (40 Å) was applied in all the simulations . In addition, a few simulations were run using the counterions method to check for charge independence.…”

“…To alleviate such effects, a relatively large vacuum space (40 Å) was applied in all the simulations . In addition, a few simulations were run using the counterions method to check for charge independence. For this purpose, counterions were inserted in the head space to neutralize the charge of the dissolved species to be adsorbed on the brucite (001) surface.…”