Bonding Effect of Partial Valence Band Depletion in Metallic [ZnSi] Layers of Li₂[ZnSi] and a Comparison to “White Graphene” h-BN

The compound Li2[ZnSi] is known to crystallize in the Li2CuAs structure type featuring graphite-like [ZnSi] layers separated by Li atoms, thus supporting the view of a Zintl phase (Li+)2[ZnSi]2–. The comparative band structure (PBE + U technique) and chemical bonding analysis with insulating h-BN using the electron localizability indicator ELI-D and the electron density reveal unexpected crystal structure–band structure effects. They lead to partial valence band depletion and the metallic conductivity of Li2[ZnSi]. As a result, the conventional polar diatomic bonds of h-BN become polar 4-atomic ones in Li2[ZnSi].