The crystal structure described by NaCaMgCr(SiO3)4 is Esseneite-derived structured and crystallizes in the monoclinic C2 space group. Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. Cr(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form CrO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-58°. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-61°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Mg(1), one Cr(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Mg(1), one Cr(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(1), one Ca(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Na(1), one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Na(1), one Cr(1), and one Si(2) atom. is represented by the CIF card [CIF]
data_NaCaMgCr(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.335
_cell_length_b   6.631
_cell_length_c   6.631
_cell_angle_alpha   84.730
_cell_angle_beta   77.679
_cell_angle_gamma   77.679
_symmetry_Int_Tables_number   1
_cell_volume   223.654
_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
  Ca  Ca0  1  0.750  0.302  0.698  1.0
  Cr  Cr1  1  0.750  0.906  0.094  1.0
  Mg  Mg2  1  0.250  0.092  0.908  1.0
  Na  Na3  1  0.250  0.701  0.299  1.0
  O  O4  1  0.370  0.031  0.197  1.0
  O  O5  1  0.130  0.803  0.969  1.0
  O  O6  1  0.650  0.967  0.802  1.0
  O  O7  1  0.850  0.198  0.033  1.0
  O  O8  1  0.501  0.337  0.370  1.0
  O  O9  1  0.999  0.630  0.663  1.0
  O  O10  1  0.502  0.664  0.640  1.0
  O  O11  1  0.998  0.360  0.336  1.0
  O  O12  1  0.184  0.113  0.614  1.0
  O  O13  1  0.316  0.386  0.887  1.0
  O  O14  1  0.808  0.895  0.385  1.0
  O  O15  1  0.692  0.615  0.105  1.0
  Si  Si16  1  0.273  0.196  0.380  1.0
  Si  Si17  1  0.227  0.620  0.804  1.0
  Si  Si18  1  0.734  0.802  0.618  1.0
  Si  Si19  1  0.766  0.382  0.198  1.0
[/CIF]
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The crystal structure described by NaCaMgCr(SiO3)4 is Esseneite-derived structured and crystallizes in the monoclinic C2 space group. Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. Cr(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form CrO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-58°. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Cr(1)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 34-61°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Mg(1), one Cr(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Mg(1), one Cr(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(1), one Ca(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Na(1), one Ca(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Mg(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Na(1), one Cr(1), and one Si(2) atom. is represented by the CIF card [CIF]
data_NaCaMgCr(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.335
_cell_length_b   6.631
_cell_length_c   6.631
_cell_angle_alpha   84.730
_cell_angle_beta   77.679
_cell_angle_gamma   77.679
_symmetry_Int_Tables_number   1
_cell_volume   223.654
_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
  Ca  Ca0  1  0.750  0.302  0.698  1.0
  Cr  Cr1  1  0.750  0.906  0.094  1.0
  Mg  Mg2  1  0.250  0.092  0.908  1.0
  Na  Na3  1  0.250  0.701  0.299  1.0
  O  O4  1  0.370  0.031  0.197  1.0
  O  O5  1  0.130  0.803  0.969  1.0
  O  O6  1  0.650  0.967  0.802  1.0
  O  O7  1  0.850  0.198  0.033  1.0
  O  O8  1  0.501  0.337  0.370  1.0
  O  O9  1  0.999  0.630  0.663  1.0
  O  O10  1  0.502  0.664  0.640  1.0
  O  O11  1  0.998  0.360  0.336  1.0
  O  O12  1  0.184  0.113  0.614  1.0
  O  O13  1  0.316  0.386  0.887  1.0
  O  O14  1  0.808  0.895  0.385  1.0
  O  O15  1  0.692  0.615  0.105  1.0
  Si  Si16  1  0.273  0.196  0.380  1.0
  Si  Si17  1  0.227  0.620  0.804  1.0
  Si  Si18  1  0.734  0.802  0.618  1.0
  Si  Si19  1  0.766  0.382  0.198  1.0
[/CIF]
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