Subnitrides with the new cluster Ba14CaN6

Abstract

Four crystalline subnitrides have been isolated by reacting Ba, (Sr), Ca in Na or NaK alloy with nitrogen from different sources. According to single crystal X-ray structure analyses these phases have compositions Na_nBa₁₄CaN₆(n= 14, 17, 21 and 22), and they contain the new Ba₁₄CaN₆ cluster, which consists of six face-sharing Ba₅CaN octahedra with Ca in the centre of the cluster. This ion cluster is inserted into different metallic substructures formed by the Na atoms. Na₂₂Ba₁₄CaN₆ exhibits a characteristic disorder which is due to frustration effects and is closely related to the disorder of an antiferromagnetic Ising spin system in a two-dimensional triangular lattice.