ERMO Cluster calculations on hyperstoichiometric Laves phase alloys and hydrides

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:arial;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">Extended Huckel molecular orbital (EHMO) cluster calculation has been performed on zirconium containing hyperstoichiometric ZrB_2+X (where B→3<i style="mso-bidi-font-style:normal">d</i> transition metal atom) hydrogen storage alloys to examine the preferential position of B atoms corresponding to hyperstoichiometry. Binding energies of clusters indicate tetrahedral sites as the preferential site for occupation by excess B atoms. Among the available sites hydrogen prefers to occupy A₂B₂ sites with partial negative charge. Energy values-show the order of stability of the hydrides to be ZrV₂> ZrMn₂ > ZrCr₂.</span>