Ca3SiBr2 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Si(1) and four equivalent Br(1) atoms to form a mixture of distorted corner and edge-sharing CaSi2Br4 octahedra. The corner-sharing octahedral tilt angles range from 0-21°. In the second Ca site, Ca(2) is bonded to two equivalent Si(1) and four equivalent Br(1) atoms to form a mixture of corner and edge-sharing CaSi2Br4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Si(1) is bonded to two equivalent Ca(2) and four equivalent Ca(1) atoms to form SiCa6 octahedra that share corners with two equivalent Si(1)Ca6 octahedra, corners with four equivalent Br(1)Ca6 octahedra, edges with two equivalent Si(1)Ca6 octahedra, and edges with ten equivalent Br(1)Ca6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. Br(1) is bonded to two equivalent Ca(2) and four equivalent Ca(1) atoms to form BrCa6 octahedra that share corners with two equivalent Si(1)Ca6 octahedra, corners with four equivalent Br(1)Ca6 octahedra, edges with five equivalent Si(1)Ca6 octahedra, and edges with seven equivalent Br(1)Ca6 octahedra. The corner-sharing octahedral tilt angles range from 0-21°.
Ca3SiBr2 is Caswellsilverite-like structured and crystallizes in the orthorhombic Immm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Si(1) and four equivalent Br(1) atoms to form a mixture of distorted corner and edge-sharing CaSi2Br4 octahedra. The corner-sharing octahedral tilt angles range from 0-21°. Both Ca(1)-Si(1) bond lengths are 2.88 Å. There are two shorter (3.01 Å) and two longer (3.37 Å) Ca(1)-Br(1) bond lengths. In the second Ca site, Ca(2) is bonded to two equivalent Si(1) and four equivalent Br(1) atoms to form a mixture of corner and edge-sharing CaSi2Br4 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Ca(2)-Si(1) bond lengths are 2.96 Å. All Ca(2)-Br(1) bond lengths are 3.28 Å. Si(1) is bonded to two equivalent Ca(2) and four equivalent Ca(1) atoms to form SiCa6 octahedra that share corners with two equivalent Si(1)Ca6 octahedra, corners with four equivalent Br(1)Ca6 octahedra, edges with two equivalent Si(1)Ca6 octahedra, and edges with ten equivalent Br(1)Ca6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. Br(1) is bonded to two equivalent Ca(2) and four equivalent Ca(1) atoms to form BrCa6 octahedra that share corners with two equivalent Si(1)Ca6 octahedra, corners with four equivalent Br(1)Ca6 octahedra, edges with five equivalent Si(1)Ca6 octahedra, and edges with seven equivalent Br(1)Ca6 octahedra. The corner-sharing octahedral tilt angles range from 0-21°.