Mg2NbN3 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(3)N6 octahedra, corners with four equivalent Nb(1)N6 octahedra, edges with two equivalent Mg(3)N6 octahedra, edges with three equivalent Mg(1)N6 octahedra, edges with three equivalent Mg(2)N6 octahedra, and edges with four equivalent Nb(1)N6 octahedra. The corner-sharing octahedral tilt angles range from 4-5°. In the second Mg site, Mg(2) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(3)N6 octahedra, corners with four equivalent Nb(1)N6 octahedra, edges with two equivalent Mg(3)N6 octahedra, edges with four equivalent Nb(1)N6 octahedra, and edges with six equivalent Mg(1)N6 octahedra. The corner-sharing octahedral tilt angles are 4°. In the third Mg site, Mg(3) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(2)N6 octahedra, corners with four equivalent Mg(1)N6 octahedra, edges with two equivalent Mg(2)N6 octahedra, edges with four equivalent Mg(1)N6 octahedra, and edges with six equivalent Nb(1)N6 octahedra. The corner-sharing octahedral tilt angles range from 4-5°. Nb(1) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form NbN6 octahedra that share corners with two equivalent Mg(2)N6 octahedra, corners with four equivalent Mg(1)N6 octahedra, edges with two equivalent Mg(2)N6 octahedra, edges with three equivalent Mg(3)N6 octahedra, edges with three equivalent Nb(1)N6 octahedra, and edges with four equivalent Mg(1)N6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Mg(2), one Mg(3), two equivalent Mg(1), and two equivalent Nb(1) atoms to form a mixture of corner and edge-sharing NMg4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the second N site, N(2) is bonded to one Mg(2), one Mg(3), two equivalent Mg(1), and two equivalent Nb(1) atoms to form a mixture of corner and edge-sharing NMg4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-4°.
Mg2NbN3 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(3)N6 octahedra, corners with four equivalent Nb(1)N6 octahedra, edges with two equivalent Mg(3)N6 octahedra, edges with three equivalent Mg(1)N6 octahedra, edges with three equivalent Mg(2)N6 octahedra, and edges with four equivalent Nb(1)N6 octahedra. The corner-sharing octahedral tilt angles range from 4-5°. Both Mg(1)-N(2) bond lengths are 2.24 Å. There are two shorter (2.21 Å) and two longer (2.28 Å) Mg(1)-N(1) bond lengths. In the second Mg site, Mg(2) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(3)N6 octahedra, corners with four equivalent Nb(1)N6 octahedra, edges with two equivalent Mg(3)N6 octahedra, edges with four equivalent Nb(1)N6 octahedra, and edges with six equivalent Mg(1)N6 octahedra. The corner-sharing octahedral tilt angles are 4°. Both Mg(2)-N(2) bond lengths are 2.18 Å. All Mg(2)-N(1) bond lengths are 2.28 Å. In the third Mg site, Mg(3) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(2)N6 octahedra, corners with four equivalent Mg(1)N6 octahedra, edges with two equivalent Mg(2)N6 octahedra, edges with four equivalent Mg(1)N6 octahedra, and edges with six equivalent Nb(1)N6 octahedra. The corner-sharing octahedral tilt angles range from 4-5°. Both Mg(3)-N(2) bond lengths are 2.24 Å. All Mg(3)-N(1) bond lengths are 2.22 Å. Nb(1) is bonded to two equivalent N(2) and four equivalent N(1) atoms to form NbN6 octahedra that share corners with two equivalent Mg(2)N6 octahedra, corners with four equivalent Mg(1)N6 octahedra, edges with two equivalent Mg(2)N6 octahedra, edges with three equivalent Mg(3)N6 octahedra, edges with three equivalent Nb(1)N6 octahedra, and edges with four equivalent Mg(1)N6 octahedra. The corner-sharing octahedral tilt angles are 4°. Both Nb(1)-N(2) bond lengths are 2.15 Å. There are two shorter (2.12 Å) and two longer (2.13 Å) Nb(1)-N(1) bond lengths. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Mg(2), one Mg(3), two equivalent Mg(1), and two equivalent Nb(1) atoms to form a mixture of corner and edge-sharing NMg4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the second N site, N(2) is bonded to one Mg(2), one Mg(3), two equivalent Mg(1), and two equivalent Nb(1) atoms to form a mixture of corner and edge-sharing NMg4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 0-4°.