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Na 30.5 Ag x Ga 60—x : A Three‐Dimensional Network Composed of Ga 3 , Ga 12 , and Ga 18 Clusters
Author(s) -
Henning Robert W.,
Corbett John D.
Publication year - 2002
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200212)628:12<2715::aid-zaac2715>3.0.co;2-a
Subject(s) - gallium , chemistry , crystallography , stacking , sodium , crystal structure , stereochemistry , organic chemistry
Single crystal X‐ray structural determinations for Na 30.5 Ag 2.6(2) Ga 57.4(2) and Na 30.5 Ag 6.4(2) Ga 53.6(2) ( P 6/ mmm , Z = 1) reveal Ga 3 triangles, Ga 12 icosahedra, and Ga 18 hexacapped hexa gonal prisms that are interconnected into a three‐dimensional network. Silver substitutes on the outer gallium sites of the Ga 18 unit and presumably stabilizes the structure by reduction of the overall electron count. The two compositions are close to the limits of a nonstoichiometry region in Ga—Ag content, whereas the sodium content does not vary significantly. Stacking of the (Ga, Ag) 18 “drums” along c rarrcreates a channel in which some typically less well localized sodium atoms reside; other sodium cations lie between the clusters and bond to gallium atoms in typical roles. Apparently isotypic analogues of this structure that are more or less well ordered are also known for other combinations of elements. Extended Hückel MO and band calculations were performed in order to gain a better understanding of the silver compound. The variable electron count observed falls in a region of relatively nonbonding states with only a small dependence on energy.