A Lanthanum-Filled Carbon-Boron Clathrate

We report a carbon-boron clathrate with composition 2 La@B6C6 (LaB3C3). Like recently reported SrB3C3,([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 composed of alternating carbon and boron atoms. The covalent nature of the B-C bonding results in a hard, incompressible framework, and owing to the balanced electron count, La3+[B3C3](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.

Automated summary

A carbon-boron clathrate with composition 2 La@B6C6 (LaB3C3) has been reported, which crystallizes in the cubic bipartite sodalite structure, with La atoms encapsulated within cages composed of alternating carbon and boron atoms. Due to the covalent nature of the B-C bonding and balanced electron count, La3+[B3C3](3-) shows improved pressure stability and exhibits semiconductor properties with an indirect band gap predicted near 1.3 eV. This study opens up possibilities for a large family of boron-stabilized, carbon-based clathrates with varied physical properties.