Charged vacancy diffusion in chromium oxide crystal: DFT and DFT+U predictions

In this work, we computationally studied the latticediffusion through the ion-vacancy exchange mechanism in α-Cr2O3 crystal using the first-principlesdensity functional theory(DFT) and DFT+U calculation methods. For both O and Crvacancies, we have identified four elementarydiffusion paths in α-Cr2O3 crystal. Our DFT+U calculations predict that the Ovacancy with charge +2 (VO2+) is stable when Fermi energy is near to valence band maximum, whereas the Crvacancy 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 forVO2+ diffusion varies from 1.18 to 2.98  eV, whereas that forVCr3−diffusion varies from 2.02 to 2.59  eV, close to experimental data. BothDFT and DFT+U results indicate that the migration energy of neutralvacancies (VO0 andVCr0) is higher than that of the chargedvacancies (VO2+ andVCr3−) 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 ofvacancies, and migration energies for chargedvacancydiffusion as compared to theDFT method.

Source: Journal of Applied Physics - December 1, 2016 Category: Physics Authors: Corinne Gray, Yinkai Lei and Guofeng Wang Source Type: research