Ca3LaSi8 is hexagonal omega structure-derived structured and crystallizes in the tetragonal P-4m2 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four Si(4,4) and eight equivalent Si(2) atoms to form a mixture of edge and face-sharing CaSi12 cuboctahedra. In the second Ca site, Ca(2) is bonded to two equivalent Si(1), two equivalent Si(2), four equivalent Si(3), and four equivalent Si(4) atoms to form CaSi12 cuboctahedra that share edges with four equivalent Ca(1)Si12 cuboctahedra, edges with four equivalent Ca(2)Si12 cuboctahedra, edges with four equivalent La(1)Si12 cuboctahedra, faces with two equivalent Ca(1)Si12 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with four equivalent Ca(2)Si12 cuboctahedra. In the third Ca site, Ca(2) is bonded to two equivalent Si(1), two equivalent Si(2), four equivalent Si(3), and four equivalent Si(4) atoms to form CaSi12 cuboctahedra that share edges with four equivalent Ca(1)Si12 cuboctahedra, edges with four equivalent Ca(2)Si12 cuboctahedra, edges with four equivalent La(1)Si12 cuboctahedra, faces with two equivalent Ca(1)Si12 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with four equivalent Ca(2)Si12 cuboctahedra. La(1) is bonded to four Si(3,3) and eight Si(1,1) atoms to form LaSi12 cuboctahedra that share edges with four equivalent La(1)Si12 cuboctahedra; edges with eight Ca(2,2)Si12 cuboctahedra; faces with four Ca(2,2)Si12 cuboctahedra; and faces with four equivalent La(1)Si12 cuboctahedra. There are seven inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent La(1), one Si(1), and two equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent Ca(1), one Si(2), and two equivalent Si(4) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Ca(2), two equivalent La(1), one Si(4), and two equivalent Si(1) atoms. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Ca(1), four equivalent Ca(2), one Si(3), and two equivalent Si(2) atoms. In the fifth Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent La(1), one Si(1), and two equivalent Si(3) atoms. In the sixth Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Ca(2), two equivalent La(1), one Si(4), and two equivalent Si(1) atoms. In the seventh Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Ca(1), four equivalent Ca(2), one Si(3), and two equivalent Si(2) atoms.
Ca3LaSi8 is hexagonal omega structure-derived structured and crystallizes in the tetragonal P-4m2 space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four Si(4,4) and eight equivalent Si(2) atoms to form a mixture of edge and face-sharing CaSi12 cuboctahedra. All Ca(1)-Si(4,4) bond lengths are 3.10 Å. All Ca(1)-Si(2) bond lengths are 3.26 Å. In the second Ca site, Ca(2) is bonded to two equivalent Si(1), two equivalent Si(2), four equivalent Si(3), and four equivalent Si(4) atoms to form CaSi12 cuboctahedra that share edges with four equivalent Ca(1)Si12 cuboctahedra, edges with four equivalent Ca(2)Si12 cuboctahedra, edges with four equivalent La(1)Si12 cuboctahedra, faces with two equivalent Ca(1)Si12 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with four equivalent Ca(2)Si12 cuboctahedra. Both Ca(2)-Si(1) bond lengths are 3.11 Å. Both Ca(2)-Si(2) bond lengths are 3.09 Å. All Ca(2)-Si(3) bond lengths are 3.27 Å. All Ca(2)-Si(4) bond lengths are 3.26 Å. In the third Ca site, Ca(2) is bonded to two equivalent Si(1), two equivalent Si(2), four equivalent Si(3), and four equivalent Si(4) atoms to form CaSi12 cuboctahedra that share edges with four equivalent Ca(1)Si12 cuboctahedra, edges with four equivalent Ca(2)Si12 cuboctahedra, edges with four equivalent La(1)Si12 cuboctahedra, faces with two equivalent Ca(1)Si12 cuboctahedra, faces with two equivalent La(1)Si12 cuboctahedra, and faces with four equivalent Ca(2)Si12 cuboctahedra. Both Ca(2)-Si(1) bond lengths are 3.11 Å. Both Ca(2)-Si(2) bond lengths are 3.09 Å. All Ca(2)-Si(3) bond lengths are 3.27 Å. All Ca(2)-Si(4) bond lengths are 3.26 Å. La(1) is bonded to four Si(3,3) and eight Si(1,1) atoms to form LaSi12 cuboctahedra that share edges with four equivalent La(1)Si12 cuboctahedra; edges with eight Ca(2,2)Si12 cuboctahedra; faces with four Ca(2,2)Si12 cuboctahedra; and faces with four equivalent La(1)Si12 cuboctahedra. All La(1)-Si(3,3) bond lengths are 3.10 Å. All La(1)-Si(1,1) bond lengths are 3.26 Å. There are seven inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent La(1), one Si(1), and two equivalent Si(3) atoms. The Si(1)-Si(1) bond length is 2.30 Å. Both Si(1)-Si(3) bond lengths are 2.41 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent Ca(1), one Si(2), and two equivalent Si(4) atoms. The Si(2)-Si(2) bond length is 2.29 Å. Both Si(2)-Si(4) bond lengths are 2.41 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Ca(2), two equivalent La(1), one Si(4), and two equivalent Si(1) atoms. The Si(3)-Si(4) bond length is 2.30 Å. In the fourth Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Ca(1), four equivalent Ca(2), one Si(3), and two equivalent Si(2) atoms. The Si(4)-Si(3) bond length is 2.30 Å. In the fifth Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Ca(2), four equivalent La(1), one Si(1), and two equivalent Si(3) atoms. Both Si(1)-Si(3) bond lengths are 2.41 Å. In the sixth Si site, Si(3) is bonded in a 9-coordinate geometry to four equivalent Ca(2), two equivalent La(1), one Si(4), and two equivalent Si(1) atoms. In the seventh Si site, Si(4) is bonded in a 9-coordinate geometry to two equivalent Ca(1), four equivalent Ca(2), one Si(3), and two equivalent Si(2) atoms. Both Si(4)-Si(2) bond lengths are 2.41 Å.