Insight into the effect of Ge modification on the oxidation of NbSi2 from first-principles calculations

The effect of Ge modification on the oxidation of NbSi2 was performed by using the first-principles method based on Density Functional Theory (DFT). The O2 molecule absorption configurations on the ideal NbSi2 (001) surface with and without Ge substitution was constructed to study the initial oxidation behavior as well as oxygen diffusion in the bulk NbSi2 cell in the late oxidation stage. Ge substitution was found to decrease the absorption energy of O2 molecule on the NbSi2 (001) surface and therefore reduce the oxidation rate in the initial oxidation stage. The further linear synchronous transit (LST) calculation revealed that Ge substitution increased the energy barrier of O atom diffusion in the bulk NbSi2 cell and decreased the oxidation rate in the late stage.