MgNi2 and MgCu2 do not form hydrides under conventional hydrogenation conditions. It is assumed that hydrogenation does not occur because the enthalpy of formation of the hydride phase is large and positive. Using Miedema's rule, we calculated the enthalpy of formation of substituted alloys based on these two compounds. For certain alloys, the enthalpy of formation is 10-20 kJ mol-1 lower. We synthesized alloys with the above calculation as a guide, however no hydride was formed under the conditions used, 4 MPa at 573 K. The size of the interstitial holes compared to the hydrogen atomic size explains these results.
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