The crystal structure described by CaCr2O4 crystallizes in the monoclinic Cm space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 4-coordinate geometry to one O(12), one O(3), and two equivalent O(10) atoms. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to one O(11), one O(4), and two equivalent O(9) atoms. In the third Ca site, Ca(3) is bonded to one O(12), one O(5), two equivalent O(10), and two equivalent O(7) atoms to form distorted CaO6 octahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra,  an edgeedge with one Cr(4)O6 octahedra,  an edgeedge with one Cr(6)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. In the fourth Ca site, Ca(4) is bonded to one O(11), one O(6), two equivalent O(8), and two equivalent O(9) atoms to form distorted CaO6 octahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra,  an edgeedge with one Cr(4)O6 octahedra,  an edgeedge with one Cr(6)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. There are six inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(11), one O(5), two equivalent O(7), and two equivalent O(9) atoms to form CrO6 octahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, edges with two equivalent Cr(4)O6 octahedra, and edges with four equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. In the second Cr site, Cr(2) is bonded to one O(12), one O(6), two equivalent O(10), and two equivalent O(8) atoms to form CrO6 octahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, edges with two equivalent Cr(6)O6 octahedra, and edges with four equivalent Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. In the third Cr site, Cr(3) is bonded to one O(10), one O(12), one O(2), one O(4), one O(6), and one O(8) atom to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. In the fourth Cr site, Cr(4) is bonded to one O(1), one O(3), two equivalent O(7), and two equivalent O(9) atoms to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with four equivalent Cr(5)O6 octahedra. In the fifth Cr site, Cr(5) is bonded to one O(1), one O(11), one O(3), one O(5), one O(7), and one O(9) atom to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(4)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. In the sixth Cr site, Cr(6) is bonded to one O(2), one O(4), two equivalent O(10), and two equivalent O(8) atoms to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with four equivalent Cr(3)O6 octahedra. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Cr(4) and two equivalent Cr(5) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Cr(6) and two equivalent Cr(3) atoms. In the third O site, O(3) is bonded to one Ca(1), one Cr(4), and two equivalent Cr(5) atoms to form a mixture of corner and edge-sharing OCaCr3 tetrahedra. In the fourth O site, O(4) is bonded to one Ca(2), one Cr(6), and two equivalent Cr(3) atoms to form a mixture of corner and edge-sharing OCaCr3 tetrahedra. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(1), and two equivalent Cr(5) atoms. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(2), and two equivalent Cr(3) atoms. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(1), one Cr(4), and one Cr(5) atom. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(2), one Cr(3), and one Cr(6) atom. In the ninth O site, O(9) is bonded to one Ca(2), one Ca(4), one Cr(1), one Cr(4), and one Cr(5) atom to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(4)CaCr3 tetrahedra,  an edgeedge with one O(3)CaCr3 tetrahedra, edges with two equivalent O(11)Ca2Cr3 trigonal bipyramids, and edges with two equivalent O(9)Ca2Cr3 trigonal bipyramids. In the tenth O site, O(10) is bonded to one Ca(1), one Ca(3), one Cr(2), one Cr(3), and one Cr(6) atom to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(3)CaCr3 tetrahedra,  an edgeedge with one O(4)CaCr3 tetrahedra, edges with two equivalent O(10)Ca2Cr3 trigonal bipyramids, and edges with two equivalent O(12)Ca2Cr3 trigonal bipyramids. In the eleventh O site, O(11) is bonded to one Ca(2), one Ca(4), one Cr(1), and two equivalent Cr(5) atoms to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(4)CaCr3 tetrahedra,  an edgeedge with one O(3)CaCr3 tetrahedra, and edges with four equivalent O(9)Ca2Cr3 trigonal bipyramids. In the twelfth O site, O(12) is bonded to one Ca(1), one Ca(3), one Cr(2), and two equivalent Cr(3) atoms to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(3)CaCr3 tetrahedra,  an edgeedge with one O(4)CaCr3 tetrahedra, and edges with four equivalent O(10)Ca2Cr3 trigonal bipyramids. is represented by the CIF file [CIF]
data_CaCr2O4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.010
_cell_length_b   6.010
_cell_length_c   6.604
_cell_angle_alpha   63.068
_cell_angle_beta   63.068
_cell_angle_gamma   60.199
_symmetry_Int_Tables_number   1
_cell_volume   176.324
_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  0.983  0.983  0.051  1.0
  Ca  Ca1  1  0.635  0.635  0.095  1.0
  Cr  Cr2  1  0.150  0.150  0.551  1.0
  Cr  Cr3  1  0.140  0.630  0.600  1.0
  Cr  Cr4  1  0.630  0.140  0.600  1.0
  Cr  Cr5  1  0.630  0.630  0.600  1.0
  O  O6  1  0.406  0.406  0.779  1.0
  O  O7  1  0.857  0.857  0.430  1.0
  O  O8  1  0.374  0.374  0.394  1.0
  O  O9  1  0.374  0.859  0.393  1.0
  O  O10  1  0.859  0.374  0.393  1.0
  O  O11  1  0.400  0.906  0.787  1.0
  O  O12  1  0.906  0.400  0.787  1.0
  O  O13  1  0.907  0.906  0.787  1.0
[/CIF]
.
The crystal structure described by CaCr2O4 crystallizes in the monoclinic Cm space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 4-coordinate geometry to one O(12), one O(3), and two equivalent O(10) atoms. In the second Ca site, Ca(2) is bonded in a 4-coordinate geometry to one O(11), one O(4), and two equivalent O(9) atoms. In the third Ca site, Ca(3) is bonded to one O(12), one O(5), two equivalent O(10), and two equivalent O(7) atoms to form distorted CaO6 octahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra,  an edgeedge with one Cr(4)O6 octahedra,  an edgeedge with one Cr(6)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. In the fourth Ca site, Ca(4) is bonded to one O(11), one O(6), two equivalent O(8), and two equivalent O(9) atoms to form distorted CaO6 octahedra that share corners with three equivalent Cr(1)O6 octahedra, corners with three equivalent Cr(2)O6 octahedra,  an edgeedge with one Cr(4)O6 octahedra,  an edgeedge with one Cr(6)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. There are six inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(11), one O(5), two equivalent O(7), and two equivalent O(9) atoms to form CrO6 octahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, edges with two equivalent Cr(4)O6 octahedra, and edges with four equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. In the second Cr site, Cr(2) is bonded to one O(12), one O(6), two equivalent O(10), and two equivalent O(8) atoms to form CrO6 octahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Ca(4)O6 octahedra, edges with two equivalent Cr(6)O6 octahedra, and edges with four equivalent Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-19°. In the third Cr site, Cr(3) is bonded to one O(10), one O(12), one O(2), one O(4), one O(6), and one O(8) atom to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. In the fourth Cr site, Cr(4) is bonded to one O(1), one O(3), two equivalent O(7), and two equivalent O(9) atoms to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with four equivalent Cr(5)O6 octahedra. In the fifth Cr site, Cr(5) is bonded to one O(1), one O(11), one O(3), one O(5), one O(7), and one O(9) atom to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(4)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. In the sixth Cr site, Cr(6) is bonded to one O(2), one O(4), two equivalent O(10), and two equivalent O(8) atoms to form CrO6 octahedra that share  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Ca(4)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with four equivalent Cr(3)O6 octahedra. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to one Cr(4) and two equivalent Cr(5) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Cr(6) and two equivalent Cr(3) atoms. In the third O site, O(3) is bonded to one Ca(1), one Cr(4), and two equivalent Cr(5) atoms to form a mixture of corner and edge-sharing OCaCr3 tetrahedra. In the fourth O site, O(4) is bonded to one Ca(2), one Cr(6), and two equivalent Cr(3) atoms to form a mixture of corner and edge-sharing OCaCr3 tetrahedra. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(1), and two equivalent Cr(5) atoms. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(2), and two equivalent Cr(3) atoms. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Cr(1), one Cr(4), and one Cr(5) atom. In the eighth O site, O(8) is bonded in a rectangular see-saw-like geometry to one Ca(4), one Cr(2), one Cr(3), and one Cr(6) atom. In the ninth O site, O(9) is bonded to one Ca(2), one Ca(4), one Cr(1), one Cr(4), and one Cr(5) atom to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(4)CaCr3 tetrahedra,  an edgeedge with one O(3)CaCr3 tetrahedra, edges with two equivalent O(11)Ca2Cr3 trigonal bipyramids, and edges with two equivalent O(9)Ca2Cr3 trigonal bipyramids. In the tenth O site, O(10) is bonded to one Ca(1), one Ca(3), one Cr(2), one Cr(3), and one Cr(6) atom to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(3)CaCr3 tetrahedra,  an edgeedge with one O(4)CaCr3 tetrahedra, edges with two equivalent O(10)Ca2Cr3 trigonal bipyramids, and edges with two equivalent O(12)Ca2Cr3 trigonal bipyramids. In the eleventh O site, O(11) is bonded to one Ca(2), one Ca(4), one Cr(1), and two equivalent Cr(5) atoms to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(4)CaCr3 tetrahedra,  an edgeedge with one O(3)CaCr3 tetrahedra, and edges with four equivalent O(9)Ca2Cr3 trigonal bipyramids. In the twelfth O site, O(12) is bonded to one Ca(1), one Ca(3), one Cr(2), and two equivalent Cr(3) atoms to form OCa2Cr3 trigonal bipyramids that share  a cornercorner with one O(3)CaCr3 tetrahedra,  an edgeedge with one O(4)CaCr3 tetrahedra, and edges with four equivalent O(10)Ca2Cr3 trigonal bipyramids. is represented by the CIF file [CIF]
data_CaCr2O4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.010
_cell_length_b   6.010
_cell_length_c   6.604
_cell_angle_alpha   63.068
_cell_angle_beta   63.068
_cell_angle_gamma   60.199
_symmetry_Int_Tables_number   1
_cell_volume   176.324
_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  0.983  0.983  0.051  1.0
  Ca  Ca1  1  0.635  0.635  0.095  1.0
  Cr  Cr2  1  0.150  0.150  0.551  1.0
  Cr  Cr3  1  0.140  0.630  0.600  1.0
  Cr  Cr4  1  0.630  0.140  0.600  1.0
  Cr  Cr5  1  0.630  0.630  0.600  1.0
  O  O6  1  0.406  0.406  0.779  1.0
  O  O7  1  0.857  0.857  0.430  1.0
  O  O8  1  0.374  0.374  0.394  1.0
  O  O9  1  0.374  0.859  0.393  1.0
  O  O10  1  0.859  0.374  0.393  1.0
  O  O11  1  0.400  0.906  0.787  1.0
  O  O12  1  0.906  0.400  0.787  1.0
  O  O13  1  0.907  0.906  0.787  1.0
[/CIF]
.