Li16Sr6Ge6N, Li16Sr6Ge6.5 and related lithium alkaline‐earth metal tetrelides : alternative filling of voids by nitride or tetrelide ions

Abstract

Large black single crystals with a metallic luster of Li16Sr6Ge6N and several other representatives of the series Li16Ae6Tt6N and Li16Ae6Tt6.5 (Ae=Ca, Sr; Tt=Si, Ge, Sn, Pb) were grown from mixtures of the respective elements with addition of binary alkaline‐earth metal nitrides or lithium nitride in the case of the nitrides. For the synthesis a modified high‐temperature centrifugation‐aided filtration (HTCAF) technique using reactive lithium melts was employed. These metallic phases crystallize in an ordered defect‐variant of the Sc11Ir4 type with selective occupation of the smaller octahedral voids in the origin (000) with N and the larger rhombic dodecahedral voids in (00 1/2) with Tt. Charge balance assuming the presence of exclusively closed shell ions for all examples accounts for an electronic excess. Diamagnetism despite metallic properties is consistent with results from electronic structure calculations.