A first-principles study of self-diffusion coefficients of fcc Ni

Abstract

Self-diffusion coefficients for fcc Ni are obtained as a function of temperature by first-principles calculations based on density functional theory within the local density approximation. To provide the minimum energy pathway and the associated saddle point structures of an elementary atomic jump, the nudged elastic band method is employed. Two magnetic settings, ferromagnetic and non-magnetic, and two vibrational contribution calculation methods, the phonon supercell approach and the Debye model, create four calculation settings for the self-diffusion coefficient in nickel. The results from these four methods are compared to each other and presented with the known experimental data. The use of the Debye model in lieu of the phonon supercell approach is shown to be a viable and computationally time saving alternative for the finite temperature thermodynamic properties. Consistent with other observations in the literature, the use of the phonon supercell approach for the calculation of the finite temperature thermodynamic properties within the LDA results in an underestimation of the diffusion coefficient with respect to experimental data. The calculated Ni self-diffusion coefficients for all four conditions in the present work are compared to a statistical consensus analysis previously performed on all known experimental self-diffusion data. With the exception of the NM phonon setting, the other three conditions fall within the 95% confidence interval for the consensus analysis.