Ca3(AlN2)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 4-coordinate geometry to two equivalent N(3), two equivalent N(4), and three equivalent N(2) atoms. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to one N(3), one N(4), and three equivalent N(1) atoms. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one N(2), one N(3), two equivalent N(1), and two equivalent N(4) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one N(1), one N(2), one N(3), and one N(4) atom to form corner-sharing AlN4 tetrahedra. In the second Al site, Al(2) is bonded to one N(3), one N(4), and two equivalent N(2) atoms to form a mixture of corner and edge-sharing AlN4 tetrahedra. There are four inequivalent N sites. In the first N site, N(1) is bonded to two equivalent Ca(3), three equivalent Ca(2), and one Al(1) atom to form distorted NCa5Al octahedra that share corners with two equivalent N(3)Ca4Al2 octahedra, corners with four equivalent N(1)Ca5Al octahedra, edges with two equivalent N(3)Ca4Al2 octahedra, and edges with two equivalent N(1)Ca5Al octahedra. The corner-sharing octahedral tilt angles range from 14-72°. In the second N site, N(2) is bonded in a 7-coordinate geometry to one Ca(3), three equivalent Ca(1), one Al(1), and two equivalent Al(2) atoms. In the third N site, N(3) is bonded to one Ca(2), one Ca(3), two equivalent Ca(1), one Al(1), and one Al(2) atom to form distorted NCa4Al2 octahedra that share corners with two equivalent N(3)Ca4Al2 octahedra, corners with two equivalent N(1)Ca5Al octahedra, and edges with two equivalent N(1)Ca5Al octahedra. The corner-sharing octahedral tilt angles range from 14-72°. In the fourth N site, N(4) is bonded in a 7-coordinate geometry to one Ca(2), two equivalent Ca(1), two equivalent Ca(3), one Al(1), and one Al(2) atom.
Ca3(AlN2)2 crystallizes in the monoclinic P2_1/c space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 4-coordinate geometry to two equivalent N(3), two equivalent N(4), and three equivalent N(2) atoms. There is one shorter (2.51 Å) and one longer (2.54 Å) Ca(1)-N(3) bond length. There is one shorter (2.43 Å) and one longer (2.78 Å) Ca(1)-N(4) bond length. There are a spread of Ca(1)-N(2) bond distances ranging from 2.51-2.94 Å. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to one N(3), one N(4), and three equivalent N(1) atoms. The Ca(2)-N(3) bond length is 2.39 Å. The Ca(2)-N(4) bond length is 3.12 Å. There are a spread of Ca(2)-N(1) bond distances ranging from 2.42-2.59 Å. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one N(2), one N(3), two equivalent N(1), and two equivalent N(4) atoms. The Ca(3)-N(2) bond length is 2.62 Å. The Ca(3)-N(3) bond length is 2.55 Å. There is one shorter (2.34 Å) and one longer (2.59 Å) Ca(3)-N(1) bond length. There is one shorter (2.62 Å) and one longer (3.04 Å) Ca(3)-N(4) bond length. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one N(1), one N(2), one N(3), and one N(4) atom to form corner-sharing AlN4 tetrahedra. The Al(1)-N(1) bond length is 1.88 Å. The Al(1)-N(2) bond length is 1.93 Å. The Al(1)-N(3) bond length is 1.87 Å. The Al(1)-N(4) bond length is 1.90 Å. In the second Al site, Al(2) is bonded to one N(3), one N(4), and two equivalent N(2) atoms to form a mixture of corner and edge-sharing AlN4 tetrahedra. The Al(2)-N(3) bond length is 1.82 Å. The Al(2)-N(4) bond length is 1.87 Å. There is one shorter (1.92 Å) and one longer (1.97 Å) Al(2)-N(2) bond length. There are four inequivalent N sites. In the first N site, N(1) is bonded to two equivalent Ca(3), three equivalent Ca(2), and one Al(1) atom to form distorted NCa5Al octahedra that share corners with two equivalent N(3)Ca4Al2 octahedra, corners with four equivalent N(1)Ca5Al octahedra, edges with two equivalent N(3)Ca4Al2 octahedra, and edges with two equivalent N(1)Ca5Al octahedra. The corner-sharing octahedral tilt angles range from 14-72°. In the second N site, N(2) is bonded in a 7-coordinate geometry to one Ca(3), three equivalent Ca(1), one Al(1), and two equivalent Al(2) atoms. In the third N site, N(3) is bonded to one Ca(2), one Ca(3), two equivalent Ca(1), one Al(1), and one Al(2) atom to form distorted NCa4Al2 octahedra that share corners with two equivalent N(3)Ca4Al2 octahedra, corners with two equivalent N(1)Ca5Al octahedra, and edges with two equivalent N(1)Ca5Al octahedra. The corner-sharing octahedral tilt angles range from 14-72°. In the fourth N site, N(4) is bonded in a 7-coordinate geometry to one Ca(2), two equivalent Ca(1), two equivalent Ca(3), one Al(1), and one Al(2) atom.