Pressure-dependent structural, mechanical, and thermal properties of magnesiowüstite: A DFT and EOS study

Using Density Functional Theory (DFT), this study, in conjunction with several equations of state (EOS), looks at how pressure affects the structural, mechanical, and thermal characteristics of Fe-rich magnesiowüstite (Mg 0.06 Fe 0.94 )O. Calculations were performed using the Vienna Ab initio Simulation Package, specifically using the GGA-PBE functional. The pressure–volume data were then fitted using the Srivastava–Pandey, Brennan–Stacey and Usual–Tait EOS models. The results indicate a smooth decrease in both the lattice constant and volume as pressure increases, which lines up with experimental data. Elastic constants as well as the bulk modulus and shear modulus, all show a steady rise, suggesting that magnesiowüstite remains mechanically stable up to 25 GPa. Thermal analysis reveals that the volume thermal expansion coefficient decreases, while the Debye temperature rises, suggesting the lattice becomes more stable under compression. When comparing the different EOS models, the Brennan–Stacey and Srivastava–Pandey models seem to reproduce the DFT results more accurately than the Usual–Tait EOS, especially at higher compression rates. Ultimately, these findings offer valuable insights into the stability of Fe-rich magnesiowüstite and provide practical guidance for choosing the right EOS when geophysically modeling the Earth’s lower mantle.