Concentration of Vacancies at Metal Oxide Surfaces: Case Study of MgO (100)

TL;DR

This study uses advanced computational methods to analyze how doping influences oxygen vacancy formation and concentration at MgO (100) surfaces, highlighting the role of space charge regions.

Contribution

It introduces a validated DFT approach with a carefully chosen exchange-correlation functional for studying vacancy concentrations at metal oxide surfaces.

Findings

Vacancy concentration is affected by doping and space charge formation.

The DFT approach is validated against CCSD(T) calculations.

Surface vacancy behavior is linked to extended space charge regions.

Abstract

We investigate effects of doping on formation energy and concentration of oxygen vacancies at a metal oxide surface, using MgO (100) as an example. Our approach employs density-functional theory, where the performance of the exchange-correlation functional is carefully analyzed, and the functional is chosen according to a fundamental condition on DFT ionization energies. The approach is further validated by CCSD(T) calculations for embedded clusters. We demonstrate that the concentration of oxygen vacancies at a doped oxide surface is largely determined by formation of a macroscopically extended space charge region.