Ca2Zn16Al crystallizes in the trigonal R3m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 19-coordinate geometry to one Zn(5), three equivalent Zn(1), three equivalent Zn(4), six equivalent Zn(2), and six equivalent Zn(3) atoms. In the second Ca site, Ca(2) is bonded in a 19-coordinate geometry to three equivalent Zn(2), three equivalent Zn(4), six equivalent Zn(1), six equivalent Zn(3), and one Al(1) atom. There are five inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to one Ca(1), two equivalent Ca(2), two equivalent Zn(2), two equivalent Zn(4), four equivalent Zn(3), and one Al(1) atom to form ZnCa3AlZn8 cuboctahedra that share corners with two equivalent Zn(1)Ca3AlZn8 cuboctahedra, corners with five equivalent Zn(4)Ca2AlZn9 cuboctahedra, corners with eight equivalent Zn(2)Ca3Zn9 cuboctahedra,  an edgeedge with one Zn(2)Ca3Zn9 cuboctahedra, edges with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, edges with four equivalent Zn(1)Ca3AlZn8 cuboctahedra, faces with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, faces with three equivalent Zn(2)Ca3Zn9 cuboctahedra, and faces with four equivalent Zn(1)Ca3AlZn8 cuboctahedra. In the second Zn site, Zn(2) is bonded to one Ca(2), two equivalent Ca(1), one Zn(5), two equivalent Zn(1), two equivalent Zn(4), and four equivalent Zn(3) atoms to form distorted ZnCa3Zn9 cuboctahedra that share corners with two equivalent Zn(2)Ca3Zn9 cuboctahedra, corners with five equivalent Zn(4)Ca2AlZn9 cuboctahedra, corners with eight equivalent Zn(1)Ca3AlZn8 cuboctahedra,  an edgeedge with one Zn(1)Ca3AlZn8 cuboctahedra, edges with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, edges with four equivalent Zn(2)Ca3Zn9 cuboctahedra, faces with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, faces with three equivalent Zn(1)Ca3AlZn8 cuboctahedra, and faces with four equivalent Zn(2)Ca3Zn9 cuboctahedra. In the third Zn site, Zn(3) is bonded in a 12-coordinate geometry to one Ca(1), one Ca(2), one Zn(5), two equivalent Zn(1), two equivalent Zn(2), two equivalent Zn(3), two equivalent Zn(4), and one Al(1) atom. In the fourth Zn site, Zn(4) is bonded to one Ca(1), one Ca(2), one Zn(5), two equivalent Zn(1), two equivalent Zn(2), four equivalent Zn(3), and one Al(1) atom to form ZnCa2AlZn9 cuboctahedra that share corners with four equivalent Zn(4)Ca2AlZn9 cuboctahedra, corners with five equivalent Zn(1)Ca3AlZn8 cuboctahedra, corners with five equivalent Zn(2)Ca3Zn9 cuboctahedra, edges with three equivalent Zn(1)Ca3AlZn8 cuboctahedra, edges with three equivalent Zn(2)Ca3Zn9 cuboctahedra, faces with three equivalent Zn(1)Ca3AlZn8 cuboctahedra, faces with three equivalent Zn(2)Ca3Zn9 cuboctahedra, and faces with four equivalent Zn(4)Ca2AlZn9 cuboctahedra. In the fifth Zn site, Zn(5) is bonded in a 14-coordinate geometry to one Ca(1), three equivalent Zn(2), three equivalent Zn(4), six equivalent Zn(3), and one Al(1) atom. Al(1) is bonded in a 14-coordinate geometry to one Ca(2), one Zn(5), three equivalent Zn(1), three equivalent Zn(4), and six equivalent Zn(3) atoms.
Ca2Zn16Al crystallizes in the trigonal R3m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 19-coordinate geometry to one Zn(5), three equivalent Zn(1), three equivalent Zn(4), six equivalent Zn(2), and six equivalent Zn(3) atoms. The Ca(1)-Zn(5) bond length is 3.11 Å. All Ca(1)-Zn(1) bond lengths are 3.20 Å. All Ca(1)-Zn(4) bond lengths are 3.42 Å. There are three shorter (3.36 Å) and three longer (3.41 Å) Ca(1)-Zn(2) bond lengths. All Ca(1)-Zn(3) bond lengths are 3.16 Å. In the second Ca site, Ca(2) is bonded in a 19-coordinate geometry to three equivalent Zn(2), three equivalent Zn(4), six equivalent Zn(1), six equivalent Zn(3), and one Al(1) atom. All Ca(2)-Zn(2) bond lengths are 3.20 Å. All Ca(2)-Zn(4) bond lengths are 3.44 Å. There are three shorter (3.36 Å) and three longer (3.40 Å) Ca(2)-Zn(1) bond lengths. All Ca(2)-Zn(3) bond lengths are 3.16 Å. The Ca(2)-Al(1) bond length is 3.18 Å. There are five inequivalent Zn sites. In the first Zn site, Zn(1) is bonded to one Ca(1), two equivalent Ca(2), two equivalent Zn(2), two equivalent Zn(4), four equivalent Zn(3), and one Al(1) atom to form ZnCa3AlZn8 cuboctahedra that share corners with two equivalent Zn(1)Ca3AlZn8 cuboctahedra, corners with five equivalent Zn(4)Ca2AlZn9 cuboctahedra, corners with eight equivalent Zn(2)Ca3Zn9 cuboctahedra,  an edgeedge with one Zn(2)Ca3Zn9 cuboctahedra, edges with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, edges with four equivalent Zn(1)Ca3AlZn8 cuboctahedra, faces with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, faces with three equivalent Zn(2)Ca3Zn9 cuboctahedra, and faces with four equivalent Zn(1)Ca3AlZn8 cuboctahedra. Both Zn(1)-Zn(2) bond lengths are 2.56 Å. Both Zn(1)-Zn(4) bond lengths are 2.62 Å. All Zn(1)-Zn(3) bond lengths are 2.72 Å. The Zn(1)-Al(1) bond length is 2.85 Å. In the second Zn site, Zn(2) is bonded to one Ca(2), two equivalent Ca(1), one Zn(5), two equivalent Zn(1), two equivalent Zn(4), and four equivalent Zn(3) atoms to form distorted ZnCa3Zn9 cuboctahedra that share corners with two equivalent Zn(2)Ca3Zn9 cuboctahedra, corners with five equivalent Zn(4)Ca2AlZn9 cuboctahedra, corners with eight equivalent Zn(1)Ca3AlZn8 cuboctahedra,  an edgeedge with one Zn(1)Ca3AlZn8 cuboctahedra, edges with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, edges with four equivalent Zn(2)Ca3Zn9 cuboctahedra, faces with three equivalent Zn(4)Ca2AlZn9 cuboctahedra, faces with three equivalent Zn(1)Ca3AlZn8 cuboctahedra, and faces with four equivalent Zn(2)Ca3Zn9 cuboctahedra. The Zn(2)-Zn(5) bond length is 2.83 Å. Both Zn(2)-Zn(4) bond lengths are 2.61 Å. There are two shorter (2.71 Å) and two longer (2.72 Å) Zn(2)-Zn(3) bond lengths. In the third Zn site, Zn(3) is bonded in a 12-coordinate geometry to one Ca(1), one Ca(2), one Zn(5), two equivalent Zn(1), two equivalent Zn(2), two equivalent Zn(3), two equivalent Zn(4), and one Al(1) atom. The Zn(3)-Zn(5) bond length is 2.96 Å. Both Zn(3)-Zn(3) bond lengths are 2.66 Å. Both Zn(3)-Zn(4) bond lengths are 2.57 Å. The Zn(3)-Al(1) bond length is 2.94 Å. In the fourth Zn site, Zn(4) is bonded to one Ca(1), one Ca(2), one Zn(5), two equivalent Zn(1), two equivalent Zn(2), four equivalent Zn(3), and one Al(1) atom to form ZnCa2AlZn9 cuboctahedra that share corners with four equivalent Zn(4)Ca2AlZn9 cuboctahedra, corners with five equivalent Zn(1)Ca3AlZn8 cuboctahedra, corners with five equivalent Zn(2)Ca3Zn9 cuboctahedra, edges with three equivalent Zn(1)Ca3AlZn8 cuboctahedra, edges with three equivalent Zn(2)Ca3Zn9 cuboctahedra, faces with three equivalent Zn(1)Ca3AlZn8 cuboctahedra, faces with three equivalent Zn(2)Ca3Zn9 cuboctahedra, and faces with four equivalent Zn(4)Ca2AlZn9 cuboctahedra. The Zn(4)-Zn(5) bond length is 2.72 Å. The Zn(4)-Al(1) bond length is 2.75 Å. In the fifth Zn site, Zn(5) is bonded in a 14-coordinate geometry to one Ca(1), three equivalent Zn(2), three equivalent Zn(4), six equivalent Zn(3), and one Al(1) atom. The Zn(5)-Al(1) bond length is 2.57 Å. Al(1) is bonded in a 14-coordinate geometry to one Ca(2), one Zn(5), three equivalent Zn(1), three equivalent Zn(4), and six equivalent Zn(3) atoms.