The compound described by MgCu2(SiO3)4 crystallizes in the triclinic P-1 space group. 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(1)O4 tetrahedra and corners with four equivalent Si(2)O4 tetrahedra. Cu(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(5) atom. 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(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-55°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cu(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Cu(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the CIF card [CIF]
data_MgCu2(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.285
_cell_length_b   5.746
_cell_length_c   7.295
_cell_angle_alpha   84.837
_cell_angle_beta   80.234
_cell_angle_gamma   84.054
_symmetry_Int_Tables_number   1
_cell_volume   216.569
_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
  Mg  Mg0  1  0.000  0.000  0.000  1.0
  Cu  Cu1  1  0.507  0.823  0.185  1.0
  Cu  Cu2  1  0.493  0.177  0.815  1.0
  Si  Si3  1  0.307  0.783  0.620  1.0
  Si  Si4  1  0.779  0.588  0.802  1.0
  Si  Si5  1  0.221  0.412  0.198  1.0
  Si  Si6  1  0.693  0.217  0.380  1.0
  O  O7  1  0.243  0.006  0.754  1.0
  O  O8  1  0.757  0.994  0.246  1.0
  O  O9  1  0.730  0.791  0.955  1.0
  O  O10  1  0.295  0.877  0.404  1.0
  O  O11  1  0.577  0.631  0.653  1.0
  O  O12  1  0.253  0.679  0.098  1.0
  O  O13  1  0.076  0.609  0.699  1.0
  O  O14  1  0.924  0.391  0.301  1.0
  O  O15  1  0.747  0.321  0.902  1.0
  O  O16  1  0.423  0.369  0.347  1.0
  O  O17  1  0.705  0.123  0.596  1.0
  O  O18  1  0.270  0.209  0.045  1.0
[/CIF]
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The compound described by MgCu2(SiO3)4 crystallizes in the triclinic P-1 space group. 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(1)O4 tetrahedra and corners with four equivalent Si(2)O4 tetrahedra. Cu(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(5) atom. 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(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 41-55°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Mg(1), one Cu(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cu(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Cu(1), and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the CIF card [CIF]
data_MgCu2(SiO3)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.285
_cell_length_b   5.746
_cell_length_c   7.295
_cell_angle_alpha   84.837
_cell_angle_beta   80.234
_cell_angle_gamma   84.054
_symmetry_Int_Tables_number   1
_cell_volume   216.569
_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
  Mg  Mg0  1  0.000  0.000  0.000  1.0
  Cu  Cu1  1  0.507  0.823  0.185  1.0
  Cu  Cu2  1  0.493  0.177  0.815  1.0
  Si  Si3  1  0.307  0.783  0.620  1.0
  Si  Si4  1  0.779  0.588  0.802  1.0
  Si  Si5  1  0.221  0.412  0.198  1.0
  Si  Si6  1  0.693  0.217  0.380  1.0
  O  O7  1  0.243  0.006  0.754  1.0
  O  O8  1  0.757  0.994  0.246  1.0
  O  O9  1  0.730  0.791  0.955  1.0
  O  O10  1  0.295  0.877  0.404  1.0
  O  O11  1  0.577  0.631  0.653  1.0
  O  O12  1  0.253  0.679  0.098  1.0
  O  O13  1  0.076  0.609  0.699  1.0
  O  O14  1  0.924  0.391  0.301  1.0
  O  O15  1  0.747  0.321  0.902  1.0
  O  O16  1  0.423  0.369  0.347  1.0
  O  O17  1  0.705  0.123  0.596  1.0
  O  O18  1  0.270  0.209  0.045  1.0
[/CIF]
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