Atomistic simulations to study point defect dynamics in bi-crystalline niobium
D Singh and P Sharma and A Parashar, MATERIALS CHEMISTRY AND PHYSICS, 255, 123628 (2020).
Niobium is an important element in Zr-Nb alloy, which is widely employed for structural material in many nuclear reactors. Superior mechanical properties and creep resistance in conjunction with low neutron cross- section, makes Zr-Nb alloy a suitable candidate for the manufacturing of pressure tubes and fuel cladding in nuclear reactors. Molecular dynamics based simulations were performed to study the point defect dynamics in niobium. Atomistic simulations were performed in the environment of classical mechanics to investigate the effect of grain boundary configurations on the point defect dynamics. Symmetric and asymmetric tilt grain boundaries were generated between the two crystals of niobium, and defect formation and migration energies were calculated as a function of distance from the grain boundary plane. A relationship between the grain boundary energies and point defect formation energies was predicted, and it was concluded that higher energy grain boundaries have higher tendency to behave as sink for point defects. Lower offset in vacancy formation energies between the initial and terminating position of vacancy, energetically favours the migration of point defects, whereas higher energy offset between bulk and grain boundaries require more energy to migrate vacancy towards the grain boundary.
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