Effects of alloying substitutions on the anti-disproportionation behavior of ZrCo alloy

We perform first-principles calculations to investigate the effects of alloying substitutions (i.e. Ti, Hf, Sc, Fe, Ni and Cu) on hydrogen-induced disproportionation of ZrCo alloy. H at the 8e site of ZrCoH3 (H(8e)) plays the key role in the disproportionation process. It is found that H(8e) prefers to form strong covalent-like binding with the neighboring Co and its substitute elements, which is distinctly different from H at the 4c2 and 8f1 sites. Alloying substitutions can restrain or accelerate the disproportionation by influencing the ZrH(8e) bond length and the size of the 8e site. Judged from this, the anti-disproportionation ability of these alloying substitutions is identified. Our results of Ti, Hf, Sc, Fe and Ni are in good agreement with the previous experimental results. It is also predicated that Cu can accelerate hydrogen-induced disproportionation of ZrCo alloy.