A lanthanum‐filled carbon–boron clathrate

We report a carbon-boron clathrate with composition 2La@B 6 C 6 (LaB 3 C 3 ). Like recently reported SrB 3 C 3 , [1] single-crystal X-ray diffraction and computational modelling indicate that the isostructural La member crystallizes in the cubic bipartite sodalite structure (Type-VII clathrate) with La atoms encapsulated within truncated octahedral cages comprised of alternating carbon and boron atoms. The covalent nature of B-C bonding results in a hard, incompressible framework, and due to the balanced electron count, La 3+ [B 3 C 3 ] 3- exhibits markedly improved pressure stability and is a semiconductor with an indirect band gap predicted near 1.3 eV. A variety of different guest atoms may potentially be substituted within Type-VII clathrate cages, presenting opportunities for a large family of boron-stabilized, carbon-based clathrates with ranging physical properties.