Na2Ga2Se3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NaSe6 octahedra that share corners with two equivalent Na(3)Se6 octahedra, corners with four equivalent Ga(1)GaSe3 tetrahedra, edges with two equivalent Na(3)Se6 octahedra, edges with three equivalent Na(1)Se6 octahedra, edges with three equivalent Na(2)Se6 octahedra, and edges with four equivalent Ga(1)GaSe3 tetrahedra. The corner-sharing octahedral tilt angles are 2°. In the second Na site, Na(2) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NaSe6 octahedra that share corners with two equivalent Na(3)Se6 octahedra, corners with four equivalent Ga(1)GaSe3 tetrahedra, edges with two equivalent Na(3)Se6 octahedra, edges with six equivalent Na(1)Se6 octahedra, and edges with four equivalent Ga(1)GaSe3 tetrahedra. The corner-sharing octahedral tilt angles are 2°. In the third Na site, Na(3) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form distorted NaSe6 octahedra that share corners with two equivalent Na(2)Se6 octahedra, corners with four equivalent Na(1)Se6 octahedra, corners with twelve equivalent Ga(1)GaSe3 tetrahedra, edges with two equivalent Na(2)Se6 octahedra, and edges with four equivalent Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 2°. Ga(1) is bonded to one Ga(1), one Se(2), and two equivalent Se(1) atoms to form distorted GaGaSe3 tetrahedra that share  a cornercorner with one Na(2)Se6 octahedra,  a cornercorner with one Se(2)Na4Ga2 octahedra, corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Se(1)Na4Ga2 octahedra, corners with three equivalent Na(3)Se6 octahedra, corners with three equivalent Ga(1)GaSe3 tetrahedra,  an edgeedge with one Na(2)Se6 octahedra, and edges with two equivalent Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 17-87°. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Ga(1) atoms to form SeNa4Ga2 octahedra that share corners with two equivalent Se(2)Na4Ga2 octahedra, corners with four equivalent Se(1)Na4Ga2 octahedra, corners with two equivalent Ga(1)GaSe3 tetrahedra, edges with four equivalent Se(2)Na4Ga2 octahedra, and edges with five equivalent Se(1)Na4Ga2 octahedra. The corner-sharing octahedral tilt angles range from 0-79°. In the second Se site, Se(2) is bonded to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Ga(1) atoms to form SeNa4Ga2 octahedra that share corners with two equivalent Se(2)Na4Ga2 octahedra, corners with four equivalent Se(1)Na4Ga2 octahedra, corners with two equivalent Ga(1)GaSe3 tetrahedra,  an edgeedge with one Se(2)Na4Ga2 octahedra, and edges with eight equivalent Se(1)Na4Ga2 octahedra. The corner-sharing octahedral tilt angles range from 0-79°.
Na2Ga2Se3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NaSe6 octahedra that share corners with two equivalent Na(3)Se6 octahedra, corners with four equivalent Ga(1)GaSe3 tetrahedra, edges with two equivalent Na(3)Se6 octahedra, edges with three equivalent Na(1)Se6 octahedra, edges with three equivalent Na(2)Se6 octahedra, and edges with four equivalent Ga(1)GaSe3 tetrahedra. The corner-sharing octahedral tilt angles are 2°. Both Na(1)-Se(2) bond lengths are 3.01 Å. There are two shorter (3.00 Å) and two longer (3.03 Å) Na(1)-Se(1) bond lengths. In the second Na site, Na(2) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NaSe6 octahedra that share corners with two equivalent Na(3)Se6 octahedra, corners with four equivalent Ga(1)GaSe3 tetrahedra, edges with two equivalent Na(3)Se6 octahedra, edges with six equivalent Na(1)Se6 octahedra, and edges with four equivalent Ga(1)GaSe3 tetrahedra. The corner-sharing octahedral tilt angles are 2°. Both Na(2)-Se(2) bond lengths are 2.97 Å. All Na(2)-Se(1) bond lengths are 3.03 Å. In the third Na site, Na(3) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form distorted NaSe6 octahedra that share corners with two equivalent Na(2)Se6 octahedra, corners with four equivalent Na(1)Se6 octahedra, corners with twelve equivalent Ga(1)GaSe3 tetrahedra, edges with two equivalent Na(2)Se6 octahedra, and edges with four equivalent Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 2°. Both Na(3)-Se(2) bond lengths are 3.19 Å. All Na(3)-Se(1) bond lengths are 3.19 Å. Ga(1) is bonded to one Ga(1), one Se(2), and two equivalent Se(1) atoms to form distorted GaGaSe3 tetrahedra that share  a cornercorner with one Na(2)Se6 octahedra,  a cornercorner with one Se(2)Na4Ga2 octahedra, corners with two equivalent Na(1)Se6 octahedra, corners with two equivalent Se(1)Na4Ga2 octahedra, corners with three equivalent Na(3)Se6 octahedra, corners with three equivalent Ga(1)GaSe3 tetrahedra,  an edgeedge with one Na(2)Se6 octahedra, and edges with two equivalent Na(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 17-87°. The Ga(1)-Ga(1) bond length is 2.41 Å. The Ga(1)-Se(2) bond length is 2.47 Å. Both Ga(1)-Se(1) bond lengths are 2.46 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Ga(1) atoms to form SeNa4Ga2 octahedra that share corners with two equivalent Se(2)Na4Ga2 octahedra, corners with four equivalent Se(1)Na4Ga2 octahedra, corners with two equivalent Ga(1)GaSe3 tetrahedra, edges with four equivalent Se(2)Na4Ga2 octahedra, and edges with five equivalent Se(1)Na4Ga2 octahedra. The corner-sharing octahedral tilt angles range from 0-79°. In the second Se site, Se(2) is bonded to one Na(2), one Na(3), two equivalent Na(1), and two equivalent Ga(1) atoms to form SeNa4Ga2 octahedra that share corners with two equivalent Se(2)Na4Ga2 octahedra, corners with four equivalent Se(1)Na4Ga2 octahedra, corners with two equivalent Ga(1)GaSe3 tetrahedra,  an edgeedge with one Se(2)Na4Ga2 octahedra, and edges with eight equivalent Se(1)Na4Ga2 octahedra. The corner-sharing octahedral tilt angles range from 0-79°.