Publication: Geometric and Electronic Structure of Closed-Shell Bimetallic A_4B_12 Clusters

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Title	Geometric and Electronic Structure of Closed-Shell Bimetallic A_4B_12 Clusters
Authors/Editors*	Yan Sun, Rene Fournier
Where published*	Physical Review A
How published*	Journal
Year*	2007
Volume	75
Number	-1
Pages	063205
Publisher
Keywords	magic clusters, bimetallic clusters, global optimization, jellium model
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Abstract	We studied, by density functional theory, a group of 16 clusters having general formula A_4B_12, where ``A'' is divalent, and ``B'', monovalent. Global optimization was done in each case followed by calculation of energy second derivatives and vibrational frequencies. The clusters have large HOMO-LUMO gaps ranging from 1.2 to 2.6 eV and other features suggesting special stability. This is consistent with the jellium model and 20 electron count. A T_d symmetry cage structure is found as the putative global minimum for Mg_4Ag_12, Mg_4Au_12, Cd_4Au_12 and Ca_4Na_12. It is also a low energy isomer (less than 0.1 eV above the global minimum) for Zn_4Au_12, Be_4Au_12, Be_4Ag_12. The T_d cage structure has ions arranged in shells, with charge +8 and +12, that match two jellium electronic shell closings, (1s^2,1p^6) and (1d^10,2s^2) with 8 and 12 electrons respectively. The importance of symmetry and ion shells is shown by the relative stability of homotops of Mg_4Ag_12.