Insight into the effect of d-orbital electron rearrangements induced by Zr–H interactions: first-principles calculations

Abstract

In nuclear reactors, hydrogen embrittlement is triggered by the formation of zirconium hydride. However, recent studies have focused on obtaining macroscale information on zirconium hydride, while fewer atomic-scale studies have been carried out on the adsorption behavior of zirconium hydride surfaces. Theoretical calculations showed that the d_xy and d_yz orbitals of the Zr atom transferred 0.82 e to the s orbital of H, facilitating the dissociative adsorption of H₂. The d_xy orbital of Zr transferred 0.34 e to the s orbital of H to form a σ bond. H₂ first decomposed on the surface of zirconium hydride through dissociative adsorption, after which it was found to bind to the zirconium hydride in the form of H atoms. The d-orbital electron rearrangements induced by Zr–H interactions led to hydrogen embrittlement. For H₂O, with increasing coverage, the H–O bond lengthened from 0.968 Å to 1.012 Å, and the center of the d-band on the ZrH surface shifted from 1.64 eV to 1.679 eV. This suggested that the strength of the H–O bonds weakened, tending towards decomposition and providing hydrogen to the zirconium hydride surface. The computational results in this paper offer theoretical guidance for understanding hydrogen embrittlement behavior.