First-principles investigation of oxidation behavior of Mo5SiB2

The high-temperature application of transition metal silicide ceramics is dramatically influenced by the pesting oxidation. However, the oxidation mechanism of Mo5SiB2 silicide is unknown due to the introduction of Boron (B). To reveal the oxidation mechanism of ternary silicides, here, we apply the first-principles approach to investigate the oxidation mechanism of Mo5SiB2. Three O-doped octahedral interstitial (OI) sites: OI(1), OI(2) and OI(3) models are considered in detail. It is found that the oxygen (O) atom is stability in Mo5SiB2. In particular, OI(3) model is more oxidation capacity than that of the CH(1) and OI(2) models. Naturally, the calculated electronic structure shows that the capacity of oxidation behavior is attributed to the structural feature and bonding state. For OI(3) model, O atom is surround by the two Si atoms and four Mo atoms. As a result, the formation of O-Si bond mainly derives from the strong localized hybridization between O and Si. This work provides an important perspective toward to understand the oxidation mechanism of Mo5SiB2 ternary silicide.