Stability of self-interstitial atoms in hcp-Zr

This paper reports the relative stability of various configurations of self-interstitial atoms (SIAs) in hcp-Zr, based on density-functional-theory calculations. In contrast to literature reports of confusing and sometimes contradicting results based on smaller calculation cells, the results here are from calculation cells that contain more than 180 atoms, and provide the most accurate and reliable prediction of the relative stability of SIAs in hcp-Zr. At the most stable configuration of basal octahedral, the formation energy of SIA is 2.73 eV, which does not change with further increase of calculation cell size. The accurate determination of the stability sequence of different SIA configurations provides key material property knowledge in understanding the microstructure evolution of the zirconium-based cladding material in nuclear reactor systems, especially for the anisotropic diffusion of the radiation-induced point defects.