La₃Si₆N₁₁

Colorless transparent single crystals of trilanthanum hexa­silicon undeca­nitro­gen, La₃Si₆N₁₁, were prepared at 0.85 MPa of N₂ and 2273 K. The title compound is isotypic with Sm₃Si₆N₁₁. Silicon-centered nitro­gen tetra­hedra form a three-dimensional network structure by sharing their corners. Layers of one type of SiN₄ tetra­hedra and slabs composed of the two different La³⁺ cations and the other type of SiN₄ tetra­hedra are alternately stacked along the c axis of the tetra­gonal unit cell. The site symmetries of the two La³⁺ cations are are ..m and 4.., respectively.