Group 2 low-valent oxides and nitrides

When metallic barium is dissolved in liquid sodium or K/Na alloy in an inert atmosphere of nitrogen, an extensive class of mixed alkali metal-barium 

Discrete [BaeN] clusters are found in the crystal structure of (BaeN)Nai6, as shown in Fig. 12.6.4. (Ba6N)Nai6 crystallizes in space group Im3m with a = 1252.7 pm and Z = 2. The Na atoms are located between the cluster units, in a manner analogous to that in the low-valent alkali metal suboxides. 

The [Bai4CaN6] cluster can be considered as a Ca-centered Bas cube with each face capped by a Ba atom, and the six N atoms are each located inside a Bas tetragonal pyramid, as shown in Fig. 12.6.6. The stmcture can be viewed alternatively as a cluster composed of the fusion of six N-centered BasCa octahedra sharing a common Ca vertex. In the synthesis of this type of cluster compounds, variation of the atomic ratio of the Na/K binary alloy system leads to a series of compounds of variable stoichiometry Bai4CaN6]Na,v withx = 7,8,14,17,21 

Arrangement of the (Ba N) clusters in the crystal structure of (BagN)Nai6. 

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