Insight into the oxidation mechanism of MoSi2: Ab-initio calculations

Transition metal silicides (TMSis) are potential candidates for high-temperature applications. However, the improvement of oxidation resistance of TMSis is still a big challenge due to the formation of volatile oxides. To overcome the important problem, we use the ab-initio calculations to study the oxidation mechanism of MoSi2 and investigate the influence of Al and Cr on the oxidation resistance of MoSi2. Two possible O-doped sites: octahedral interstitial site and tetrahedral interstitial site are considered. We find that oxygen prefers to occupy the TI-2 site because of the strong charge interaction between Si and O. We further examine the alloying effect in MoSi2. Cr-doping is a thermodynamically stable in contrary to Al-doping is a thermodynamically instable. Importantly, alloying elements can effectively improve the oxidation resistance of MoSi2 because those alloying elements enhance the localized hybridization between Si and O. Finally, our work can open up a new path to improve the oxidation resistance of TMSis high-temperature materials.