Li3Cr3SiO8 crystallizes in the monoclinic P2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form LiO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with four equivalent Si(1)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with four equivalent Li(2)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-6°. In the second Li site, Li(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form LiO6 octahedra that share corners with six equivalent Cr(2)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Li(2)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-16°. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Li(1)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Si(1)O6 octahedra, edges with four equivalent Li(2)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with six equivalent Li(2)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Li(2)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-16°. Si(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form SiO6 octahedra that share corners with four equivalent Li(1)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with four equivalent Li(2)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 5°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Li(2), two equivalent Cr(2), and one Si(1) atom to form OLi2Cr2Si square pyramids that share corners with four equivalent O(2)Li3Cr3 octahedra,  a cornercorner with one O(1)Li2Cr2Si square pyramid, corners with four equivalent O(3)Li2Cr2Si square pyramids, edges with two equivalent O(2)Li3Cr3 octahedra, edges with two equivalent O(1)Li2Cr2Si square pyramids, and edges with four equivalent O(3)Li2Cr2Si square pyramids. The corner-sharing octahedral tilt angles range from 7-8°. In the second O site, O(2) is bonded to one Li(1), two equivalent Li(2), one Cr(1), and two equivalent Cr(2) atoms to form OLi3Cr3 octahedra that share corners with two equivalent O(2)Li3Cr3 octahedra, corners with four equivalent O(1)Li2Cr2Si square pyramids, edges with two equivalent O(2)Li3Cr3 octahedra, edges with two equivalent O(1)Li2Cr2Si square pyramids, and edges with eight equivalent O(3)Li2Cr2Si square pyramids. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Cr(1), one Cr(2), and one Si(1) atom to form OLi2Cr2Si square pyramids that share corners with two equivalent O(1)Li2Cr2Si square pyramids, corners with seven equivalent O(3)Li2Cr2Si square pyramids, edges with four equivalent O(2)Li3Cr3 octahedra, edges with two equivalent O(1)Li2Cr2Si square pyramids, and edges with two equivalent O(3)Li2Cr2Si square pyramids.
Li3Cr3SiO8 crystallizes in the monoclinic P2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form LiO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with four equivalent Si(1)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with four equivalent Li(2)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 5-6°. Both Li(1)-O(2) bond lengths are 2.08 Å. All Li(1)-O(3) bond lengths are 2.32 Å. In the second Li site, Li(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form LiO6 octahedra that share corners with six equivalent Cr(2)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Li(2)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-16°. Both Li(2)-O(1) bond lengths are 2.10 Å. Both Li(2)-O(2) bond lengths are 2.22 Å. Both Li(2)-O(3) bond lengths are 2.12 Å. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2) and four equivalent O(3) atoms to form CrO6 octahedra that share corners with two equivalent Li(1)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Si(1)O6 octahedra, edges with four equivalent Li(2)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. Both Cr(1)-O(2) bond lengths are 2.04 Å. All Cr(1)-O(3) bond lengths are 2.01 Å. In the second Cr site, Cr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form CrO6 octahedra that share corners with six equivalent Li(2)O6 octahedra, edges with two equivalent Li(1)O6 octahedra, edges with two equivalent Li(2)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Si(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-16°. Both Cr(2)-O(1) bond lengths are 2.03 Å. Both Cr(2)-O(2) bond lengths are 2.03 Å. Both Cr(2)-O(3) bond lengths are 2.03 Å. Si(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form SiO6 octahedra that share corners with four equivalent Li(1)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with four equivalent Li(2)O6 octahedra, and edges with four equivalent Cr(2)O6 octahedra. The corner-sharing octahedral tilt angles are 5°. Both Si(1)-O(1) bond lengths are 1.79 Å. All Si(1)-O(3) bond lengths are 1.85 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Li(2), two equivalent Cr(2), and one Si(1) atom to form OLi2Cr2Si square pyramids that share corners with four equivalent O(2)Li3Cr3 octahedra,  a cornercorner with one O(1)Li2Cr2Si square pyramid, corners with four equivalent O(3)Li2Cr2Si square pyramids, edges with two equivalent O(2)Li3Cr3 octahedra, edges with two equivalent O(1)Li2Cr2Si square pyramids, and edges with four equivalent O(3)Li2Cr2Si square pyramids. The corner-sharing octahedral tilt angles range from 7-8°. In the second O site, O(2) is bonded to one Li(1), two equivalent Li(2), one Cr(1), and two equivalent Cr(2) atoms to form OLi3Cr3 octahedra that share corners with two equivalent O(2)Li3Cr3 octahedra, corners with four equivalent O(1)Li2Cr2Si square pyramids, edges with two equivalent O(2)Li3Cr3 octahedra, edges with two equivalent O(1)Li2Cr2Si square pyramids, and edges with eight equivalent O(3)Li2Cr2Si square pyramids. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Cr(1), one Cr(2), and one Si(1) atom to form OLi2Cr2Si square pyramids that share corners with two equivalent O(1)Li2Cr2Si square pyramids, corners with seven equivalent O(3)Li2Cr2Si square pyramids, edges with four equivalent O(2)Li3Cr3 octahedra, edges with two equivalent O(1)Li2Cr2Si square pyramids, and edges with two equivalent O(3)Li2Cr2Si square pyramids.