La4Ag2Se7 crystallizes in the monoclinic Pc space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(4), one Se(5), one Se(7), and two equivalent Se(6) atoms. In the second La site, La(2) is bonded in a 8-coordinate geometry to one Se(2), one Se(5), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(6) atoms. In the third La site, La(3) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(4), one Se(5), two equivalent Se(3), and two equivalent Se(6) atoms. In the fourth La site, La(4) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(4), one Se(5), and two equivalent Se(7) atoms. There are two inequivalent Ag sites. In the first Ag site, Ag(1) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(4), one Se(5), and one Se(7) atom. In the second Ag site, Ag(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(5), two equivalent Se(4), and two equivalent Se(7) atoms. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded to one La(1), one La(3), one La(4), two equivalent La(2), and one Ag(1) atom to form distorted SeLa5Ag octahedra that share corners with two equivalent Se(5)La4Ag2 octahedra, corners with two equivalent Se(1)La5Ag octahedra, corners with two equivalent Se(3)La5Ag octahedra, corners with three equivalent Se(2)La4Ag2 octahedra, edges with two equivalent Se(4)La3Ag3 octahedra, edges with two equivalent Se(5)La4Ag2 octahedra,  a faceface with one Se(2)La4Ag2 octahedra, and faces with two equivalent Se(3)La5Ag octahedra. The corner-sharing octahedral tilt angles range from 15-60°. In the second Se site, Se(2) is bonded to one La(1), one La(2), one La(3), one La(4), one Ag(1), and one Ag(2) atom to form distorted SeLa4Ag2 octahedra that share  a cornercorner with one Se(3)La5Ag octahedra, corners with two equivalent Se(4)La3Ag3 octahedra, corners with three equivalent Se(1)La5Ag octahedra,  an edgeedge with one Se(3)La5Ag octahedra, edges with two equivalent Se(4)La3Ag3 octahedra,  a faceface with one Se(1)La5Ag octahedra,  a faceface with one Se(3)La5Ag octahedra, and faces with two equivalent Se(5)La4Ag2 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. In the third Se site, Se(3) is bonded to one La(1), two equivalent La(2), two equivalent La(3), and one Ag(1) atom to form distorted SeLa5Ag octahedra that share  a cornercorner with one Se(4)La3Ag3 octahedra,  a cornercorner with one Se(2)La4Ag2 octahedra, corners with two equivalent Se(1)La5Ag octahedra, corners with four equivalent Se(5)La4Ag2 octahedra,  an edgeedge with one Se(2)La4Ag2 octahedra,  an edgeedge with one Se(5)La4Ag2 octahedra, edges with two equivalent Se(3)La5Ag octahedra,  a faceface with one Se(4)La3Ag3 octahedra,  a faceface with one Se(2)La4Ag2 octahedra, and faces with two equivalent Se(1)La5Ag octahedra. The corner-sharing octahedral tilt angles range from 20-60°. In the fourth Se site, Se(4) is bonded to one La(1), one La(3), one La(4), one Ag(1), and two equivalent Ag(2) atoms to form distorted SeLa3Ag3 octahedra that share  a cornercorner with one Se(3)La5Ag octahedra, corners with two equivalent Se(4)La3Ag3 octahedra, corners with two equivalent Se(2)La4Ag2 octahedra, corners with three equivalent Se(5)La4Ag2 octahedra, edges with two equivalent Se(2)La4Ag2 octahedra, edges with two equivalent Se(1)La5Ag octahedra,  a faceface with one Se(5)La4Ag2 octahedra, and  a faceface with one Se(3)La5Ag octahedra. The corner-sharing octahedral tilt angles range from 15-63°. In the fifth Se site, Se(5) is bonded to one La(1), one La(2), one La(3), one La(4), one Ag(1), and one Ag(2) atom to form distorted SeLa4Ag2 octahedra that share corners with two equivalent Se(1)La5Ag octahedra, corners with three equivalent Se(4)La3Ag3 octahedra, corners with four equivalent Se(3)La5Ag octahedra,  an edgeedge with one Se(3)La5Ag octahedra, edges with two equivalent Se(1)La5Ag octahedra,  a faceface with one Se(4)La3Ag3 octahedra, and faces with two equivalent Se(2)La4Ag2 octahedra. The corner-sharing octahedral tilt angles range from 15-56°. In the sixth Se site, Se(6) is bonded in a 6-coordinate geometry to two equivalent La(1), two equivalent La(2), and two equivalent La(3) atoms. In the seventh Se site, Se(7) is bonded in a 6-coordinate geometry to one La(1), two equivalent La(4), one Ag(1), and two equivalent Ag(2) atoms.
La4Ag2Se7 crystallizes in the monoclinic Pc space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(4), one Se(5), one Se(7), and two equivalent Se(6) atoms. The La(1)-Se(1) bond length is 3.12 Å. The La(1)-Se(2) bond length is 3.04 Å. The La(1)-Se(3) bond length is 3.18 Å. The La(1)-Se(4) bond length is 3.11 Å. The La(1)-Se(5) bond length is 3.17 Å. The La(1)-Se(7) bond length is 3.13 Å. There is one shorter (3.06 Å) and one longer (3.52 Å) La(1)-Se(6) bond length. In the second La site, La(2) is bonded in a 8-coordinate geometry to one Se(2), one Se(5), two equivalent Se(1), two equivalent Se(3), and two equivalent Se(6) atoms. The La(2)-Se(2) bond length is 3.47 Å. The La(2)-Se(5) bond length is 2.98 Å. There is one shorter (3.10 Å) and one longer (3.26 Å) La(2)-Se(1) bond length. There is one shorter (3.02 Å) and one longer (3.06 Å) La(2)-Se(3) bond length. There is one shorter (3.09 Å) and one longer (3.20 Å) La(2)-Se(6) bond length. In the third La site, La(3) is bonded in a 8-coordinate geometry to one Se(1), one Se(2), one Se(4), one Se(5), two equivalent Se(3), and two equivalent Se(6) atoms. The La(3)-Se(1) bond length is 3.07 Å. The La(3)-Se(2) bond length is 3.13 Å. The La(3)-Se(4) bond length is 3.04 Å. The La(3)-Se(5) bond length is 3.11 Å. There is one shorter (3.10 Å) and one longer (3.34 Å) La(3)-Se(3) bond length. There is one shorter (3.11 Å) and one longer (3.46 Å) La(3)-Se(6) bond length. In the fourth La site, La(4) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(4), one Se(5), and two equivalent Se(7) atoms. The La(4)-Se(1) bond length is 3.04 Å. The La(4)-Se(2) bond length is 3.07 Å. The La(4)-Se(4) bond length is 3.24 Å. The La(4)-Se(5) bond length is 2.94 Å. There is one shorter (2.87 Å) and one longer (2.98 Å) La(4)-Se(7) bond length. There are two inequivalent Ag sites. In the first Ag site, Ag(1) is bonded in a 6-coordinate geometry to one Se(1), one Se(2), one Se(3), one Se(4), one Se(5), and one Se(7) atom. The Ag(1)-Se(1) bond length is 3.06 Å. The Ag(1)-Se(2) bond length is 3.21 Å. The Ag(1)-Se(3) bond length is 3.23 Å. The Ag(1)-Se(4) bond length is 2.76 Å. The Ag(1)-Se(5) bond length is 3.07 Å. The Ag(1)-Se(7) bond length is 2.77 Å. In the second Ag site, Ag(2) is bonded in a 6-coordinate geometry to one Se(2), one Se(5), two equivalent Se(4), and two equivalent Se(7) atoms. The Ag(2)-Se(2) bond length is 2.75 Å. The Ag(2)-Se(5) bond length is 2.99 Å. There is one shorter (2.85 Å) and one longer (3.28 Å) Ag(2)-Se(4) bond length. There is one shorter (3.14 Å) and one longer (3.36 Å) Ag(2)-Se(7) bond length. There are seven inequivalent Se sites. In the first Se site, Se(1) is bonded to one La(1), one La(3), one La(4), two equivalent La(2), and one Ag(1) atom to form distorted SeLa5Ag octahedra that share corners with two equivalent Se(5)La4Ag2 octahedra, corners with two equivalent Se(1)La5Ag octahedra, corners with two equivalent Se(3)La5Ag octahedra, corners with three equivalent Se(2)La4Ag2 octahedra, edges with two equivalent Se(4)La3Ag3 octahedra, edges with two equivalent Se(5)La4Ag2 octahedra,  a faceface with one Se(2)La4Ag2 octahedra, and faces with two equivalent Se(3)La5Ag octahedra. The corner-sharing octahedral tilt angles range from 15-60°. In the second Se site, Se(2) is bonded to one La(1), one La(2), one La(3), one La(4), one Ag(1), and one Ag(2) atom to form distorted SeLa4Ag2 octahedra that share  a cornercorner with one Se(3)La5Ag octahedra, corners with two equivalent Se(4)La3Ag3 octahedra, corners with three equivalent Se(1)La5Ag octahedra,  an edgeedge with one Se(3)La5Ag octahedra, edges with two equivalent Se(4)La3Ag3 octahedra,  a faceface with one Se(1)La5Ag octahedra,  a faceface with one Se(3)La5Ag octahedra, and faces with two equivalent Se(5)La4Ag2 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. In the third Se site, Se(3) is bonded to one La(1), two equivalent La(2), two equivalent La(3), and one Ag(1) atom to form distorted SeLa5Ag octahedra that share  a cornercorner with one Se(4)La3Ag3 octahedra,  a cornercorner with one Se(2)La4Ag2 octahedra, corners with two equivalent Se(1)La5Ag octahedra, corners with four equivalent Se(5)La4Ag2 octahedra,  an edgeedge with one Se(2)La4Ag2 octahedra,  an edgeedge with one Se(5)La4Ag2 octahedra, edges with two equivalent Se(3)La5Ag octahedra,  a faceface with one Se(4)La3Ag3 octahedra,  a faceface with one Se(2)La4Ag2 octahedra, and faces with two equivalent Se(1)La5Ag octahedra. The corner-sharing octahedral tilt angles range from 20-60°. In the fourth Se site, Se(4) is bonded to one La(1), one La(3), one La(4), one Ag(1), and two equivalent Ag(2) atoms to form distorted SeLa3Ag3 octahedra that share  a cornercorner with one Se(3)La5Ag octahedra, corners with two equivalent Se(4)La3Ag3 octahedra, corners with two equivalent Se(2)La4Ag2 octahedra, corners with three equivalent Se(5)La4Ag2 octahedra, edges with two equivalent Se(2)La4Ag2 octahedra, edges with two equivalent Se(1)La5Ag octahedra,  a faceface with one Se(5)La4Ag2 octahedra, and  a faceface with one Se(3)La5Ag octahedra. The corner-sharing octahedral tilt angles range from 15-63°. In the fifth Se site, Se(5) is bonded to one La(1), one La(2), one La(3), one La(4), one Ag(1), and one Ag(2) atom to form distorted SeLa4Ag2 octahedra that share corners with two equivalent Se(1)La5Ag octahedra, corners with three equivalent Se(4)La3Ag3 octahedra, corners with four equivalent Se(3)La5Ag octahedra,  an edgeedge with one Se(3)La5Ag octahedra, edges with two equivalent Se(1)La5Ag octahedra,  a faceface with one Se(4)La3Ag3 octahedra, and faces with two equivalent Se(2)La4Ag2 octahedra. The corner-sharing octahedral tilt angles range from 15-56°. In the sixth Se site, Se(6) is bonded in a 6-coordinate geometry to two equivalent La(1), two equivalent La(2), and two equivalent La(3) atoms. In the seventh Se site, Se(7) is bonded in a 6-coordinate geometry to one La(1), two equivalent La(4), one Ag(1), and two equivalent Ag(2) atoms.