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In this work, we computationally studied the lattice diffusion through the ion-vacancy exchange mechanism in α-Cr2O3 crystal using the first-principles density functional theory (DFT) and DFT+U calculation methods. For both O and Cr vacancies, we have identified four elementary diffusion paths in α-Cr2O3 crystal. Our DFT+U calculations predict that the O vacancy with charge +2 (VO2+) is stable when Fermi energy is near to valence band maximum, whereas the Cr vacancy with charge −3 (VCr3−) is stable when Fermi energy is close to conduction band minimum. Moreover, the DFT+U calculations predict that the migration energy for VO2+  diffusion varies from 1.18 to 2.98 eV, whereas that for VCr3− diffusion varies from 2.02 to 2.59 eV, close to experimental data. Both DFT and DFT+U results indicate that the migration energy of neutral vacancies (VO0 and VCr0) is higher than that of the charged vacancies (VO2+ and VCr3−) along any diffusive path. Importantly, it is found that the DFT+U method describes α-Cr2O3 crystal better in terms of the magnetism, band gap, charge state of vacancies, and migration energies for charged vacancy diffusion as compared to the DFT method.

In this study, we used atomistic simulation methods to examine solid-solution phase formation rules for CoCrFeNi high entropy alloy. Using the Monte Carlo simulations based on the modified embedded atom method (MEAM) potentials, we sampled the thermodynamically equilibrium structures of the CoCrFeNi alloy and further predicted that the CoCrFeNi alloy could form a solid solution phase with high configurational entropy of 1.329R at 1373 K. Furthermore, we examined the stability of this solid solution phase of the CoCrFeNi alloy against the well-recognized solid-solution phase formation rules by varying the MEAM potentials and thus tuning the atom size and mixing enthalpy in the alloy. Our simulation results revealed that it required atom size difference effect d j j < 0:05 and mixing enthalpy effect À10 kJ/mol < DH % 0 kJ/mol for the modeled CoCrFeNi alloy to remain a single solid solution phase.