The crystal structure described by MgEr2Nb2O8 is beta indium sulfide-derived structured and crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share edges with two equivalent Er(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. In the second Er site, Er(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form ErO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Er(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Er(2)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. In the second Nb site, Nb(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Er(2)O6 octahedra, and edges with two equivalent Nb(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Er(1), one Er(2), and one Nb(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Er(2), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Er(1), and one Nb(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Er(2), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing OErMgNb2 trigonal pyramids. is represented by the CIF card [CIF]
data_Er2MgNb2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.221
_cell_length_b   6.301
_cell_length_c   5.498
_cell_angle_alpha   90.000
_cell_angle_beta   79.214
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   177.666
_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
  Er  Er0  1  0.250  0.951  0.000  1.0
  Er  Er1  1  0.750  0.353  0.000  1.0
  Mg  Mg2  1  0.750  0.086  0.500  1.0
  Nb  Nb3  1  0.250  0.388  0.500  1.0
  Nb  Nb4  1  0.750  0.623  0.500  1.0
  O  O5  1  0.047  0.143  0.754  1.0
  O  O6  1  0.015  0.574  0.750  1.0
  O  O7  1  0.485  0.574  0.250  1.0
  O  O8  1  0.453  0.143  0.246  1.0
  O  O9  1  0.567  0.847  0.716  1.0
  O  O10  1  0.549  0.344  0.688  1.0
  O  O11  1  0.951  0.344  0.312  1.0
  O  O12  1  0.933  0.847  0.284  1.0
[/CIF]
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The crystal structure described by MgEr2Nb2O8 is beta indium sulfide-derived structured and crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share edges with two equivalent Er(2)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. In the second Er site, Er(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form ErO6 octahedra that share corners with two equivalent Nb(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Nb(1)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form NbO6 octahedra that share corners with two equivalent Er(2)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Er(2)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 23°. In the second Nb site, Nb(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NbO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Er(2)O6 octahedra, and edges with two equivalent Nb(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Er(1), one Er(2), and one Nb(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Er(2), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Er(1), and one Nb(2) atom. In the fourth O site, O(4) is bonded to one Mg(1), one Er(2), one Nb(1), and one Nb(2) atom to form a mixture of distorted edge and corner-sharing OErMgNb2 trigonal pyramids. is represented by the CIF card [CIF]
data_Er2MgNb2O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.221
_cell_length_b   6.301
_cell_length_c   5.498
_cell_angle_alpha   90.000
_cell_angle_beta   79.214
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   177.666
_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
  Er  Er0  1  0.250  0.951  0.000  1.0
  Er  Er1  1  0.750  0.353  0.000  1.0
  Mg  Mg2  1  0.750  0.086  0.500  1.0
  Nb  Nb3  1  0.250  0.388  0.500  1.0
  Nb  Nb4  1  0.750  0.623  0.500  1.0
  O  O5  1  0.047  0.143  0.754  1.0
  O  O6  1  0.015  0.574  0.750  1.0
  O  O7  1  0.485  0.574  0.250  1.0
  O  O8  1  0.453  0.143  0.246  1.0
  O  O9  1  0.567  0.847  0.716  1.0
  O  O10  1  0.549  0.344  0.688  1.0
  O  O11  1  0.951  0.344  0.312  1.0
  O  O12  1  0.933  0.847  0.284  1.0
[/CIF]
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