Ca2Ni7 crystallizes in the trigonal R-3m space group. There are six inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4,4); and six equivalent Ni(5) atoms. In the second Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2), three equivalent Ni(3), six equivalent Ni(4), and six equivalent Ni(5) atoms. In the third Ca site, Ca(2) is bonded in a 12-coordinate geometry to three equivalent Ni(1) and nine equivalent Ni(5) atoms. In the fourth Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4); and six equivalent Ni(5) atoms. In the fifth Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4); and six equivalent Ni(5) atoms. In the sixth Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4,4); and six equivalent Ni(5) atoms. There are seven inequivalent Ni sites. In the first Ni site, Ni(4) is bonded to four Ca(1,1); two equivalent Ni(2); two equivalent Ni(3); and four equivalent Ni(4) atoms to form NiCa4Ni8 cuboctahedra that share corners with four equivalent Ni(4)Ca4Ni8 cuboctahedra, corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra, edges with two equivalent Ni(4)Ca4Ni8 cuboctahedra, edges with eight equivalent Ni(5)Ca5Ni7 cuboctahedra, faces with two equivalent Ni(5)Ca5Ni7 cuboctahedra, and faces with eight equivalent Ni(4)Ca4Ni8 cuboctahedra. In the second Ni site, Ni(1) is bonded to six equivalent Ca(2) and six equivalent Ni(5) atoms to form NiCa6Ni6 cuboctahedra that share corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra, edges with six equivalent Ni(1)Ca6Ni6 cuboctahedra, and faces with eighteen equivalent Ni(5)Ca5Ni7 cuboctahedra. In the third Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Ca(1), three equivalent Ni(4), and three equivalent Ni(5) atoms. In the fourth Ni site, Ni(3) is bonded in a 9-coordinate geometry to three equivalent Ca(1); three Ni(4,4,4); and three equivalent Ni(5) atoms. In the fifth Ni site, Ni(4) is bonded to four equivalent Ca(1), two equivalent Ni(2), two equivalent Ni(3), and four equivalent Ni(4) atoms to form NiCa4Ni8 cuboctahedra that share corners with four equivalent Ni(4)Ca4Ni8 cuboctahedra, corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra, edges with two equivalent Ni(4)Ca4Ni8 cuboctahedra, edges with eight equivalent Ni(5)Ca5Ni7 cuboctahedra, faces with two equivalent Ni(5)Ca5Ni7 cuboctahedra, and faces with eight equivalent Ni(4)Ca4Ni8 cuboctahedra. In the sixth Ni site, Ni(5) is bonded to two equivalent Ca(1), three equivalent Ca(2), one Ni(1), one Ni(2), one Ni(3), and four equivalent Ni(5) atoms to form distorted NiCa5Ni7 cuboctahedra that share corners with two equivalent Ni(1)Ca6Ni6 cuboctahedra; corners with six Ni(4,4,4)Ca4Ni8 cuboctahedra; corners with nine equivalent Ni(5)Ca5Ni7 cuboctahedra; edges with four Ni(4,4)Ca4Ni8 cuboctahedra; edges with four equivalent Ni(5)Ca5Ni7 cuboctahedra;  a faceface with one Ni(4)Ca4Ni8 cuboctahedra; faces with three equivalent Ni(1)Ca6Ni6 cuboctahedra; and faces with ten equivalent Ni(5)Ca5Ni7 cuboctahedra. In the seventh Ni site, Ni(4) is bonded to four Ca(1,1); two equivalent Ni(2); two equivalent Ni(3); and four Ni(4,4) atoms to form NiCa4Ni8 cuboctahedra that share corners with four equivalent Ni(4)Ca4Ni8 cuboctahedra; corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra; edges with two equivalent Ni(4)Ca4Ni8 cuboctahedra; edges with eight equivalent Ni(5)Ca5Ni7 cuboctahedra; faces with two equivalent Ni(5)Ca5Ni7 cuboctahedra; and faces with eight Ni(4,4)Ca4Ni8 cuboctahedra.
Ca2Ni7 crystallizes in the trigonal R-3m space group. There are six inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4,4); and six equivalent Ni(5) atoms. All Ca(1)-Ni(2) bond lengths are 2.88 Å. All Ca(1)-Ni(3) bond lengths are 2.88 Å. All Ca(1)-Ni(4,4,4) bond lengths are 3.10 Å. All Ca(1)-Ni(5) bond lengths are 3.24 Å. In the second Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2), three equivalent Ni(3), six equivalent Ni(4), and six equivalent Ni(5) atoms. All Ca(1)-Ni(2) bond lengths are 2.88 Å. All Ca(1)-Ni(3) bond lengths are 2.88 Å. All Ca(1)-Ni(4) bond lengths are 3.10 Å. All Ca(1)-Ni(5) bond lengths are 3.24 Å. In the third Ca site, Ca(2) is bonded in a 12-coordinate geometry to three equivalent Ni(1) and nine equivalent Ni(5) atoms. All Ca(2)-Ni(1) bond lengths are 2.96 Å. There are six shorter (2.86 Å) and three longer (3.09 Å) Ca(2)-Ni(5) bond lengths. In the fourth Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4); and six equivalent Ni(5) atoms. All Ca(1)-Ni(2) bond lengths are 2.88 Å. All Ca(1)-Ni(3) bond lengths are 2.88 Å. All Ca(1)-Ni(4,4) bond lengths are 3.10 Å. All Ca(1)-Ni(5) bond lengths are 3.24 Å. In the fifth Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4); and six equivalent Ni(5) atoms. All Ca(1)-Ni(2) bond lengths are 2.88 Å. All Ca(1)-Ni(3) bond lengths are 2.88 Å. All Ca(1)-Ni(4,4) bond lengths are 3.10 Å. All Ca(1)-Ni(5) bond lengths are 3.24 Å. In the sixth Ca site, Ca(1) is bonded in a 18-coordinate geometry to three equivalent Ni(2); three equivalent Ni(3); six Ni(4,4,4); and six equivalent Ni(5) atoms. All Ca(1)-Ni(2) bond lengths are 2.88 Å. All Ca(1)-Ni(3) bond lengths are 2.88 Å. All Ca(1)-Ni(4,4,4) bond lengths are 3.10 Å. All Ca(1)-Ni(5) bond lengths are 3.24 Å. There are seven inequivalent Ni sites. In the first Ni site, Ni(4) is bonded to four Ca(1,1); two equivalent Ni(2); two equivalent Ni(3); and four equivalent Ni(4) atoms to form NiCa4Ni8 cuboctahedra that share corners with four equivalent Ni(4)Ca4Ni8 cuboctahedra, corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra, edges with two equivalent Ni(4)Ca4Ni8 cuboctahedra, edges with eight equivalent Ni(5)Ca5Ni7 cuboctahedra, faces with two equivalent Ni(5)Ca5Ni7 cuboctahedra, and faces with eight equivalent Ni(4)Ca4Ni8 cuboctahedra. Both Ni(4)-Ni(2) bond lengths are 2.45 Å. Both Ni(4)-Ni(3) bond lengths are 2.42 Å. All Ni(4)-Ni(4) bond lengths are 2.49 Å. In the second Ni site, Ni(1) is bonded to six equivalent Ca(2) and six equivalent Ni(5) atoms to form NiCa6Ni6 cuboctahedra that share corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra, edges with six equivalent Ni(1)Ca6Ni6 cuboctahedra, and faces with eighteen equivalent Ni(5)Ca5Ni7 cuboctahedra. All Ni(1)-Ni(5) bond lengths are 2.51 Å. In the third Ni site, Ni(2) is bonded in a 9-coordinate geometry to three equivalent Ca(1), three equivalent Ni(4), and three equivalent Ni(5) atoms. All Ni(2)-Ni(4) bond lengths are 2.45 Å. All Ni(2)-Ni(5) bond lengths are 2.41 Å. In the fourth Ni site, Ni(3) is bonded in a 9-coordinate geometry to three equivalent Ca(1); three Ni(4,4,4); and three equivalent Ni(5) atoms. Both Ni(3)-Ni(4,4) bond lengths are 2.42 Å. All Ni(3)-Ni(5) bond lengths are 2.43 Å. In the fifth Ni site, Ni(4) is bonded to four equivalent Ca(1), two equivalent Ni(2), two equivalent Ni(3), and four equivalent Ni(4) atoms to form NiCa4Ni8 cuboctahedra that share corners with four equivalent Ni(4)Ca4Ni8 cuboctahedra, corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra, edges with two equivalent Ni(4)Ca4Ni8 cuboctahedra, edges with eight equivalent Ni(5)Ca5Ni7 cuboctahedra, faces with two equivalent Ni(5)Ca5Ni7 cuboctahedra, and faces with eight equivalent Ni(4)Ca4Ni8 cuboctahedra. All Ni(4)-Ni(4) bond lengths are 2.49 Å. In the sixth Ni site, Ni(5) is bonded to two equivalent Ca(1), three equivalent Ca(2), one Ni(1), one Ni(2), one Ni(3), and four equivalent Ni(5) atoms to form distorted NiCa5Ni7 cuboctahedra that share corners with two equivalent Ni(1)Ca6Ni6 cuboctahedra; corners with six Ni(4,4,4)Ca4Ni8 cuboctahedra; corners with nine equivalent Ni(5)Ca5Ni7 cuboctahedra; edges with four Ni(4,4)Ca4Ni8 cuboctahedra; edges with four equivalent Ni(5)Ca5Ni7 cuboctahedra;  a faceface with one Ni(4)Ca4Ni8 cuboctahedra; faces with three equivalent Ni(1)Ca6Ni6 cuboctahedra; and faces with ten equivalent Ni(5)Ca5Ni7 cuboctahedra. There are two shorter (2.49 Å) and two longer (2.50 Å) Ni(5)-Ni(5) bond lengths. In the seventh Ni site, Ni(4) is bonded to four Ca(1,1); two equivalent Ni(2); two equivalent Ni(3); and four Ni(4,4) atoms to form NiCa4Ni8 cuboctahedra that share corners with four equivalent Ni(4)Ca4Ni8 cuboctahedra; corners with twelve equivalent Ni(5)Ca5Ni7 cuboctahedra; edges with two equivalent Ni(4)Ca4Ni8 cuboctahedra; edges with eight equivalent Ni(5)Ca5Ni7 cuboctahedra; faces with two equivalent Ni(5)Ca5Ni7 cuboctahedra; and faces with eight Ni(4,4)Ca4Ni8 cuboctahedra. Both Ni(4)-Ni(2) bond lengths are 2.45 Å. Both Ni(4)-Ni(4) bond lengths are 2.49 Å.