Étude de l'élasticité de (MgO) par le calcul des constantes élastique sous pression

Abstract

The objective of this study is to investigate the elasticity of magnesium oxide (MgO) under hydrostatic pressure. To this end, we employed the CASTEP code, based on Density Functional Theory (DFT) and the generalized gradient approximation. First, we determined the phase transition pressure by calculating enthalpy as a function of pressure; the transition occurs at approximately 400 GPa. We calculated the equations of state for both the B1 and B2 crystalline phases, and the final stage of the study focused on calculating the elastic moduli, seismic velocities (Vp and Vs), and seismic anisotropy of MgO. Our calculations show that the elastic constants of magnesium oxide vary linearly with increasing pressure for each phase. The C11 modulus is significantly higher than the C12 and C44 moduli, indicating that deformation along the [100] axis is the most difficult—particularly in the B1 phase compared to the B2 phase. The C44 modulus remains the lowest in both phases (above 50 GPa), indicating that the easiest mode of deformation for MgO is shearing along the (100) plane, again more so in the B1 phase than in the B2 phase.