Impurity diffusion coefficients in BCC Nb from first-principles calculations

Abstract

Impurity diffusion is fundamentally important for understanding many phenomena in metallic alloys, such as nucleation and growth of precipitates, solidification and creep, thus plays a crucial role in improving materials properties and new materials design. However, the coverage of the impurity diffusion database from experiments and theoretical calculations, especially for Nb-based alloys, is still far from perfect and requires further investigation. Therefore, we calculated the temperature-dependent impurity diffusion coefficients of ten elements in body-centered cubic (BCC) Nb by using the first-principles calculations based on the density functional theory (DFT) and the nine-frequency model. The migration barriers were determined by the climbing image nudged elastic band method (CI-NEB) with a single image. The attempt frequency for each atomic jump was obtained with the Vineyard's transition state theory. The calculated impurity diffusion coefficients were corrected based on the deviation of the calculated and experimental self-diffusion coefficients. We found good agreement between calculated results and available experimental data in the literature.