Ca3Ni3Si2 crystallizes in the orthorhombic Pnma space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one Ni(3), two equivalent Ni(1), one Si(1), and three equivalent Si(2) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one Ni(3), two equivalent Ni(2), one Si(1), and two equivalent Si(2) atoms. In the third Ca site, Ca(3) is bonded in a 10-coordinate geometry to two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), and four equivalent Si(1) atoms. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 10-coordinate geometry to two equivalent Ca(1), two equivalent Ca(3), one Ni(2), two equivalent Ni(3), one Si(2), and two equivalent Si(1) atoms. In the second Ni site, Ni(2) is bonded in a 10-coordinate geometry to two equivalent Ca(2), two equivalent Ca(3), one Ni(1), two equivalent Ni(3), one Si(2), and two equivalent Si(1) atoms. In the third Ni site, Ni(3) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), two equivalent Ni(1), two equivalent Ni(2), two equivalent Si(1), and two equivalent Si(2) atoms to form distorted NiCa4Si4Ni4 cuboctahedra that share corners with two equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, edges with four equivalent Si(1)Ca6Ni6 cuboctahedra, faces with two equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, and faces with two equivalent Si(1)Ca6Ni6 cuboctahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one Ca(1), one Ca(2), four equivalent Ca(3), two equivalent Ni(1), two equivalent Ni(2), and two equivalent Ni(3) atoms to form distorted SiCa6Ni6 cuboctahedra that share corners with four equivalent Si(1)Ca6Ni6 cuboctahedra, edges with four equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, faces with two equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, and faces with four equivalent Si(1)Ca6Ni6 cuboctahedra. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Ca(2), three equivalent Ca(1), one Ni(1), one Ni(2), and two equivalent Ni(3) atoms.
Ca3Ni3Si2 crystallizes in the orthorhombic Pnma space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one Ni(3), two equivalent Ni(1), one Si(1), and three equivalent Si(2) atoms. The Ca(1)-Ni(3) bond length is 3.00 Å. Both Ca(1)-Ni(1) bond lengths are 2.99 Å. The Ca(1)-Si(1) bond length is 3.25 Å. There are two shorter (2.99 Å) and one longer (3.24 Å) Ca(1)-Si(2) bond length. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one Ni(3), two equivalent Ni(2), one Si(1), and two equivalent Si(2) atoms. The Ca(2)-Ni(3) bond length is 3.01 Å. Both Ca(2)-Ni(2) bond lengths are 3.01 Å. The Ca(2)-Si(1) bond length is 3.27 Å. Both Ca(2)-Si(2) bond lengths are 2.99 Å. In the third Ca site, Ca(3) is bonded in a 10-coordinate geometry to two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), and four equivalent Si(1) atoms. There is one shorter (2.80 Å) and one longer (2.96 Å) Ca(3)-Ni(1) bond length. There is one shorter (2.81 Å) and one longer (2.95 Å) Ca(3)-Ni(2) bond length. Both Ca(3)-Ni(3) bond lengths are 3.07 Å. There are two shorter (3.25 Å) and two longer (3.27 Å) Ca(3)-Si(1) bond lengths. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 10-coordinate geometry to two equivalent Ca(1), two equivalent Ca(3), one Ni(2), two equivalent Ni(3), one Si(2), and two equivalent Si(1) atoms. The Ni(1)-Ni(2) bond length is 2.44 Å. Both Ni(1)-Ni(3) bond lengths are 2.58 Å. The Ni(1)-Si(2) bond length is 2.25 Å. Both Ni(1)-Si(1) bond lengths are 2.31 Å. In the second Ni site, Ni(2) is bonded in a 10-coordinate geometry to two equivalent Ca(2), two equivalent Ca(3), one Ni(1), two equivalent Ni(3), one Si(2), and two equivalent Si(1) atoms. Both Ni(2)-Ni(3) bond lengths are 2.58 Å. The Ni(2)-Si(2) bond length is 2.25 Å. Both Ni(2)-Si(1) bond lengths are 2.30 Å. In the third Ni site, Ni(3) is bonded to one Ca(1), one Ca(2), two equivalent Ca(3), two equivalent Ni(1), two equivalent Ni(2), two equivalent Si(1), and two equivalent Si(2) atoms to form distorted NiCa4Si4Ni4 cuboctahedra that share corners with two equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, edges with four equivalent Si(1)Ca6Ni6 cuboctahedra, faces with two equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, and faces with two equivalent Si(1)Ca6Ni6 cuboctahedra. There is one shorter (2.58 Å) and one longer (2.59 Å) Ni(3)-Si(1) bond length. Both Ni(3)-Si(2) bond lengths are 2.40 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one Ca(1), one Ca(2), four equivalent Ca(3), two equivalent Ni(1), two equivalent Ni(2), and two equivalent Ni(3) atoms to form distorted SiCa6Ni6 cuboctahedra that share corners with four equivalent Si(1)Ca6Ni6 cuboctahedra, edges with four equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, faces with two equivalent Ni(3)Ca4Si4Ni4 cuboctahedra, and faces with four equivalent Si(1)Ca6Ni6 cuboctahedra. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Ca(2), three equivalent Ca(1), one Ni(1), one Ni(2), and two equivalent Ni(3) atoms.