Intermetallic compounds based on hydrogen absorbing elements usually form stable hydrides. This is the case for ${\mathrm{PdZr}}_2$. Surprisingly, ${\mathrm{ZrPd}}_2$ does not absorb hydrogen although both compounds have the same crystal structure and satisfy the empirical geometrical criteria for hydride formation. Results of ab initio calculations reveal an unanticipated purely electronic origin. These results have implications in the search for new intermetallics for hydrogen storage.

• Received 14 January 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.056403

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