Ca3(AlSi)2 crystallizes in the orthorhombic Immm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to eight equivalent Al(1) and four equivalent Si(1) atoms to form a mixture of distorted edge and face-sharing CaAl8Si4 cuboctahedra. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to two equivalent Al(1) and five equivalent Si(1) atoms. Al(1) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent Ca(1), one Al(1), and two equivalent Si(1) atoms. Si(1) is bonded in a 7-coordinate geometry to two equivalent Ca(1), five equivalent Ca(2), and two equivalent Al(1) atoms.
Ca3(AlSi)2 crystallizes in the orthorhombic Immm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to eight equivalent Al(1) and four equivalent Si(1) atoms to form a mixture of distorted edge and face-sharing CaAl8Si4 cuboctahedra. All Ca(1)-Al(1) bond lengths are 3.31 Å. All Ca(1)-Si(1) bond lengths are 3.51 Å. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to two equivalent Al(1) and five equivalent Si(1) atoms. Both Ca(2)-Al(1) bond lengths are 3.15 Å. There is one shorter (3.14 Å) and four longer (3.15 Å) Ca(2)-Si(1) bond lengths. Al(1) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent Ca(1), one Al(1), and two equivalent Si(1) atoms. The Al(1)-Al(1) bond length is 2.55 Å. Both Al(1)-Si(1) bond lengths are 2.48 Å. Si(1) is bonded in a 7-coordinate geometry to two equivalent Ca(1), five equivalent Ca(2), and two equivalent Al(1) atoms.