DOE OSTI2020
CaGeN2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Ca2+ is bonded to five equivalent N3- atoms to form a mixture of corner and edge-sharing CaN5 square pyramids. There are one shorter (2.33 Å) and four longer (2.62 Å) Ca–N bond lengths. Ge4+ is bonded in a 5-coordinate geometry to five N3- atoms. There is one shorter (1.83 Å) and four longer (2.02 Å) Ge–N bond length. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded to four equivalent Ge4+ atoms to form distorted NGe4 trigonal pyramids that share corners with four equivalent NCa5Ge octahedra, corners with four equivalent NGe4 trigonal pyramids, and edges with four equivalent NGe4 trigonal pyramids. The corner-sharing octahedral tilt angles are 66°. In the second N3- site, N3- is bonded to five equivalent Ca2+ and one Ge4+ atom to form NCa5Ge octahedra that share corners with four equivalent NCa5Ge octahedra, corners with four equivalent NGe4 trigonal pyramids, and edges with eight equivalent NCa5Ge octahedra. The corner-sharing octahedral tilt angles are 6°.