First-principles calculations of relaxation volumes and stability of charged defects in magnesium oxide at high pressure
Phys. Rev. B 113, 054110 – Published 13 February, 2026
DOI: https://doi.org/10.1103/f2qg-2gs5
Abstract
The relaxation volume of point defects is known to be an important parameter for diffusion processes and interactions between defects in crystals. In this study, we investigate the effect of high pressure on the formation enthalpy and relaxation volume of point defects in magnesium oxide using first-principles calculations. Although energy corrections in charged systems are by now well established, the reliable evaluation of stress and pressure in charged periodic systems necessitates specific corrections to address the ill-defined electrostatic potential in first-principles codes. In this study, we extend a methodology based on the determination of the so-called hydrostatic absolute deformation potential applicable at high pressure. We show that, at ambient pressure, oxygen vacancies are associated with a positive relaxation volume, whereas the relaxation volume of magnesium vacancies is negative. With increasing pressure, all vacancy relaxation volumes decrease and become negative above 150 GPa. In addition, we demonstrate that the stability field of charged vacancies exhibits a pressure-dependent evolution, which correlates with the reduction of ionicity in MgO under pressure.
