The structure described by 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. is represented by the CIF file [CIF]
data_Ca2Ni7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.989
_cell_length_b   4.989
_cell_length_c   12.293
_cell_angle_alpha   78.293
_cell_angle_beta   78.293
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   257.559
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.949  0.949  0.154  1.0
  Ca  Ca1  1  0.051  0.051  0.846  1.0
  Ca  Ca2  1  0.852  0.852  0.445  1.0
  Ca  Ca3  1  0.148  0.148  0.555  1.0
  Ni  Ni4  1  0.500  0.500  0.500  1.0
  Ni  Ni5  1  0.722  0.722  0.835  1.0
  Ni  Ni6  1  0.278  0.278  0.165  1.0
  Ni  Ni7  1  0.612  0.612  0.163  1.0
  Ni  Ni8  1  0.388  0.388  0.837  1.0
  Ni  Ni9  1  0.000  0.500  0.000  1.0
  Ni  Ni10  1  0.500  0.000  0.000  1.0
  Ni  Ni11  1  0.500  0.500  0.000  1.0
  Ni  Ni12  1  0.392  0.392  0.327  1.0
  Ni  Ni13  1  0.890  0.392  0.327  1.0
  Ni  Ni14  1  0.392  0.890  0.327  1.0
  Ni  Ni15  1  0.608  0.608  0.673  1.0
  Ni  Ni16  1  0.110  0.608  0.673  1.0
  Ni  Ni17  1  0.608  0.110  0.673  1.0
[/CIF]
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The structure described by 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. is represented by the CIF file [CIF]
data_Ca2Ni7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.989
_cell_length_b   4.989
_cell_length_c   12.293
_cell_angle_alpha   78.293
_cell_angle_beta   78.293
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   257.559
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Ca  Ca0  1  0.949  0.949  0.154  1.0
  Ca  Ca1  1  0.051  0.051  0.846  1.0
  Ca  Ca2  1  0.852  0.852  0.445  1.0
  Ca  Ca3  1  0.148  0.148  0.555  1.0
  Ni  Ni4  1  0.500  0.500  0.500  1.0
  Ni  Ni5  1  0.722  0.722  0.835  1.0
  Ni  Ni6  1  0.278  0.278  0.165  1.0
  Ni  Ni7  1  0.612  0.612  0.163  1.0
  Ni  Ni8  1  0.388  0.388  0.837  1.0
  Ni  Ni9  1  0.000  0.500  0.000  1.0
  Ni  Ni10  1  0.500  0.000  0.000  1.0
  Ni  Ni11  1  0.500  0.500  0.000  1.0
  Ni  Ni12  1  0.392  0.392  0.327  1.0
  Ni  Ni13  1  0.890  0.392  0.327  1.0
  Ni  Ni14  1  0.392  0.890  0.327  1.0
  Ni  Ni15  1  0.608  0.608  0.673  1.0
  Ni  Ni16  1  0.110  0.608  0.673  1.0
  Ni  Ni17  1  0.608  0.110  0.673  1.0
[/CIF]
.