Evaluation of the structure and properties for the high-temperature phase of zirconium from the atomistic simulations

We study peculiarities of phase transitions in zirconium and properties of the high-temperature beta-Zr phase. To get a more detailed understanding of the structure and thermodynamic characteristics of zirconium, we perform atomistic simulations with two different interatomic potentials. Both potentials demonstrate an unstable behavior of beta-Zr phase at low temperatures but explain this phenomenon by substantially different reasons. For one of the potentials, the mechanical instability takes place, and for the other potential the instability of beta-Zr is purely dynamic. Review of the available experimental data shows that it is more correct to describe beta-Zr through the low-temperature dynamic instability. The structure peculiarity discussed for beta-Zr leads to a local non-cubic symmetry of this phase and low formation energy of the self-interstitial atoms. The latter leads to fast atomic self-diffusion that is consistent with existing data. We also perform deformation tests for the atomistic models of beta-Zr-Nb alloys taking into account the studied details of alpha-beta transition.