The U4Re7Si6 type – Trends in electronic structure and chemical bonding

• U4Re7Si6-prototype shows flexibility for substitutions and changes in the valence electron count.
• DFT calculations for several A4T7X6 compounds show common bonding characteristics.
• Main T1-X and T2-X bonding due to crystal chemistry with T1@X6 and T2@X4 polyhedra.
• U4T7X6 are found stabilized in a ferromagnetic configuration, for T = Ru and X = Ge, As.

The electronic structures and chemical bonding of selected ternary compounds of the A4T7X6 family (of U4Re7Si6-type) intermetallics have been studied by ab initio methods. The calculations for two series: Mg4Rh7P6, Sc4Co7Ge6, Ti4Co7Ge6 and uranium containing U4Re7Si6, U4Ru7Ge6, and U4Ru7As6 show common bonding characteristics pertaining to main T1–X and T2–X interactions (T = transition metal and X = p-element) due to the peculiar crystal chemistry with T1@X6 and T2@X4 coordination polyhedra. The uranium compounds are found to be stabilized in a spin polarized ferromagnetic configuration, especially for U4Ru7Ge6 (in agreement with experiment) and U4Ru7As6.

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