A Computational Study to Determine and Compare the Structural and Elastic Properties of MgO, CaO and the Earth Material at PREM Pressures up to the Outer Core’s Limits of the Earth

Abstract

By changing the pressure up to 140 GPa, we aimed in this work to study some parameters of the structural and elastic properties of MgO and CaO and compare them with those provided by the PREM model. This was calculated using the DFT method, the GGA approximation, as we chose from among several functions the modern function PBEsol. Starting with geometric optimization, we confirmed that the phase transformation of calcium oxide from phase B1 to B2 occurs at 59.2 GPa, while manganese oxide remains stable in its first phase, B1. Despite the slight difference in our results from the previous study, whether experimental or computational, especially at zero pressure, the agreement confirms the validity of these results. Also, after we chose the degree of the polynomials most appropriate to the change of these parameters with changes in pressure, we were able to accurately compare the parameters of these two oxides and between them and what is provided by the PREM model, in addition to determining the values of these parameters at the basic discontinuities in the subsurface to contribute to the global data base.