Iron-Centered Ten-VertexGermanium Clusters: The Ubiquityof Low Energy Pentagonal Prismatic Structures with Various SkeletalElectron Counts.

One of the most significant recent developments (in 2009)is the discovery of the clusters M@Ge103–(M = Fe, Co) in which the outer Ge10polyhedron is apentagonal prism rather than a deltahedral structure of the type predictedby the Wade–Mingos rules. Consistent with this experimentalobservation, density functional theory shows the lowest energy structuresto be pentagonal prisms for the iron-centered clusters Fe@Ge10zin all nine charge states ranging from−5 to . This contrasts with the previously studied cobalt-centeredgermanium clusters Co@Ge10zfor which the lowest energy structures are pentagonal prisms onlyfor the electron richest systems where zranges from−3 to −5. The C3vstructures derived from the tetracapped trigonal prism foundas lowest energy structures of the electron poorer Co@Ge10z(z= 0, −1,−2) systems are higher energy structures for the iron-centeredgermanium clusters Fe@Ge10z(z= 0, −1, −2). The strong energeticpreference for pentagonal prismatic structures in the Fe@Ge10zclusters can be attributed to the needfor the larger volume of the pentagonal prism relative to other 10-vertexclosed polyhedra to accommodate the interstitial iron atom. [ABSTRACT FROM AUTHOR]