Alloying effects on the electronic structure of ZrMn2 intermetallic hydride

The electronic structures of ZrMn2 intermetallic hydride containing a variety of alloying elements are investigated by the DV-Xα cluster method. It is found that hydrogen atom makes a strong chemical bond with Mn atoms rather than Zr atoms in pure ZrMn2 hydride. The substitution of alloying elements for Mn atoms scarcely modifies the total bond strength between hydrogen and metal atoms, despite the fact that hydrogen absorption and desorption characteristics change significantly with alloying elements. On the contrary, both the Mn-Mn and the Zr-Mn interactions are greatly affected by alloying. It is shown that the ratio of the Zr-Mn bond order to the Mn-Mn bond order in a small tetrahedron containing a hydrogen atom, correlates well with experimental data of the equilibrium hydrogen pressure of alloyed ZrMn2. (orig.)