Molecular dynamics calculations of anion diffusion in nitrogen-doped yttria-stabilized zirconia

Anion diffusion was simulated in the system (Y0.2Zr0.8)–(O1.72N0.15) with the molecular dynamics (MD) technique using the program DL_POLY, employing empirical potentials of the Buckingham type. To describe nitrogen migration, nitrogen potentials had to be developed, assuming the interaction of charged nitrogen shells with a mass of 0.15 amu with cores. Comparing experimental and simulated anion diffusivities, the diffusion coefficients were found to be of similar order. However, nitrogen diffuses five times slower than oxygen according to the computer simulation, while experimentally, the difference is reported to be smaller. Calculated activation enthalpies were 1.2 and 1.4 eV, respectively, for the two elements, with pre-exponential factors of 10−5 and 10−4 cm2/s, respectively.