The crystal structure described by MgTm2Cr2O8 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Tm(1)O7 pentagonal bipyramids, corners with two equivalent Cr(1)O4 tetrahedra, edges with four equivalent Tm(1)O7 pentagonal bipyramids, and edges with two equivalent Cr(1)O4 tetrahedra. Tm(1) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted TmO7 pentagonal bipyramids that share  a cornercorner with one Mg(1)O6 octahedra, corners with five equivalent Cr(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with three equivalent Tm(1)O7 pentagonal bipyramids, and  an edgeedge with one Cr(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 34°. Cr(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with five equivalent Tm(1)O7 pentagonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Tm(1)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 63°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Tm(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Tm(1), and one Cr(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Tm(1), and one Cr(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Tm(1), and one Cr(1) atom to form distorted corner-sharing OTm2MgCr trigonal pyramids. is represented by the CIF file [CIF]
data_Tm2MgCr2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.884
_cell_length_b   6.215
_cell_length_c   6.215
_cell_angle_alpha   110.828
_cell_angle_beta   103.946
_cell_angle_gamma   116.101
_symmetry_Int_Tables_number   1
_cell_volume   168.022
_cell_formula_units_Z   1
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
  Tm  Tm0  1  0.136  0.836  0.267  1.0
  Tm  Tm1  1  0.864  0.131  0.699  1.0
  Mg  Mg2  1  0.000  0.258  0.258  1.0
  Cr  Cr3  1  0.410  0.655  0.789  1.0
  Cr  Cr4  1  0.590  0.379  0.245  1.0
  O  O5  1  0.839  0.750  0.452  1.0
  O  O6  1  0.373  0.754  0.542  1.0
  O  O7  1  0.772  0.831  0.009  1.0
  O  O8  1  0.790  0.350  0.054  1.0
  O  O9  1  0.627  0.170  0.381  1.0
  O  O10  1  0.210  0.265  0.561  1.0
  O  O11  1  0.161  0.614  0.912  1.0
  O  O12  1  0.228  0.237  0.059  1.0
[/CIF]
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The crystal structure described by MgTm2Cr2O8 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MgO6 octahedra that share corners with two equivalent Tm(1)O7 pentagonal bipyramids, corners with two equivalent Cr(1)O4 tetrahedra, edges with four equivalent Tm(1)O7 pentagonal bipyramids, and edges with two equivalent Cr(1)O4 tetrahedra. Tm(1) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted TmO7 pentagonal bipyramids that share  a cornercorner with one Mg(1)O6 octahedra, corners with five equivalent Cr(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, edges with three equivalent Tm(1)O7 pentagonal bipyramids, and  an edgeedge with one Cr(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 34°. Cr(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with five equivalent Tm(1)O7 pentagonal bipyramids,  an edgeedge with one Mg(1)O6 octahedra, and  an edgeedge with one Tm(1)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 63°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Tm(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Tm(1), and one Cr(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Tm(1), and one Cr(1) atom. In the fourth O site, O(4) is bonded to one Mg(1), two equivalent Tm(1), and one Cr(1) atom to form distorted corner-sharing OTm2MgCr trigonal pyramids. is represented by the CIF file [CIF]
data_Tm2MgCr2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.884
_cell_length_b   6.215
_cell_length_c   6.215
_cell_angle_alpha   110.828
_cell_angle_beta   103.946
_cell_angle_gamma   116.101
_symmetry_Int_Tables_number   1
_cell_volume   168.022
_cell_formula_units_Z   1
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
  Tm  Tm0  1  0.136  0.836  0.267  1.0
  Tm  Tm1  1  0.864  0.131  0.699  1.0
  Mg  Mg2  1  0.000  0.258  0.258  1.0
  Cr  Cr3  1  0.410  0.655  0.789  1.0
  Cr  Cr4  1  0.590  0.379  0.245  1.0
  O  O5  1  0.839  0.750  0.452  1.0
  O  O6  1  0.373  0.754  0.542  1.0
  O  O7  1  0.772  0.831  0.009  1.0
  O  O8  1  0.790  0.350  0.054  1.0
  O  O9  1  0.627  0.170  0.381  1.0
  O  O10  1  0.210  0.265  0.561  1.0
  O  O11  1  0.161  0.614  0.912  1.0
  O  O12  1  0.228  0.237  0.059  1.0
[/CIF]
.