MSINDO study of acid promoted dissolution of planar MgO and NiO surfaces

Abstract

Despite the structural similarity, MgO is fast dissolving in low pH solution, whereas NiO is slow dissolving under the same conditions. In addition, the planar MgO (100) surface immediately reconstructs to form pits and protrusions, whereas this behavior has not been observed with NiO (100). Our previous study, using the semiempirical self-consistent field molecular orbital (SCFMO) method MSINDO showed that it was possible for MgO dissolution but not NiO dissolution to occur via the migration of a metal-oxygen pair to an ex situ position. However, we have now found a more energetically favorable and realistic dissolution mechanism involving the dissociation of a water molecule (adsorbed on a metal site) prior to migration. Products from this dissociation (H and OH) weaken adjacent metal-oxygen bonds. Dissociation of a second adsorbed water molecule is required to complete the process. For both oxides, the energy barrier determined from the energy profile of the metal-oxygen pair migration was found to be lower than the activation energy of water dissociation at the planar surface as reported in previous study. This would suggest that the dissociation of water molecules at the planar surface is rate-determining in the surface restructuring step of dissolution. It was demonstrated that surface restructuring and dissolution of MgO is possible whereas highly improbable for NiO, in agreement with experimental observations.

The effect of iron and copper impurities on the wettability of sphalerite (110) surface

“…Details of the implementation of the CCM and the refinement of selected zinc and sulfur parameters can be found elsewhere 33–36. This combination of method and model has been used successfully in recent studies on surface properties, in particular doping and the interaction with water 37–39…”

Large-Scale Computations in Chemistry: A Bird’s Eye View of a Vibrant Field

“…The MSINDO method was utilized extensively by Bredow and Jug. They performed molecular dynamics studies employing this semiempirical Hamiltonian for various systems and processes, such as Si cluster structure, adsorbate–surface interactions, , vacancy diffusion in solid-state materials, and chemical transformations. , The applicability of the method to complex and relatively large systems of varying chemical nature and the ability to perform long-time molecular dynamics simulations emphasize MSINDO advantages. To be fair, we should note that similar computational performance and comparable accuracy can be expected for other semiempirical methods.…”