A DFT study of defects in paramagnetic Cr 2 O 3

Cr O is not only a promising functional material, but also an essential barrier to protect chromia-forming alloys against high temperature corrosion. The Cr O protecting layer grows slowly defect-mediated diffusion. Several types of point defects could be responsible for the diffusion process depending on the oxidation environment, resulting in different semiconductor characters of chromia. According to the literature, the defect chemistry of Cr O in the antiferromagnetic (AFM) state has been well studied using density functional theory (DFT) calculations but not in the paramagnetic (PM) state, which is the fundamental state of Cr O above 318 K. PM Cr O is simulated in this study using special quasi-random structures (SQS). The formation energies of intrinsic point defects in AFM and PM Cr O are calculated to study the defect chemistry and the semiconductor properties in different oxidation environments (temperature and oxygen partial pressure ) using a thermodynamic model. It is found that O vacancies and insulating-type Cr O , in which commensurate electrons and holes are dominant before atomic defects are more favorable at high temperatures and at low , while Cr vacancies and p-type Cr O are more favorable at low temperatures and at high , according to the calculations both in AFM and PM Cr O . However, the limits of dominant zones for defects and for semiconductor characters shift to higher temperatures or lower in PM state calculations.