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Abstract

We use atomistic simulations to characterize self-diffusion in two bcc metals of high technological demand: molybdenum and bcc iron. It was experimentally observed in 1979 that the temperature dependence of self-diffusion coefficient D(T) in Mo can not be described by the universal Arrhenius function. In this work, we use molecular dynamics to determine possible reasons of such phenomenon. Properties of single vacancies contributing in the self-diffusion in Mo are considered with two different interatomic potentials. We computed migration barriers, vacancy formation energies, and diffusivities in a wide temperature range (up to 2600K). Also, we performed direct simulations of the self-diffusion coefficients in bcc Mo. Computed data are consistent with each other and allow to suggest that curvature of D(T) rises from the behaviour of the vacancy formation free energies in Mo. The work also contains results dealing with the investigation of the defect diffusivities in bcc Fe.