The structure described by MgEr6Ta2O14 crystallizes in the monoclinic C2 space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. In the second Er site, Er(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms. In the third Er site, Er(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. In the fourth Er site, Er(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-55°. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 26°. In the second Ta site, Ta(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 26°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Er(1), one Er(2), one Er(3), and one Er(4) atom to form distorted OEr4Mg trigonal bipyramids that share corners with four equivalent O(3)Er3Ta tetrahedra, corners with four equivalent O(7)Er4 tetrahedra,  a cornercorner with one O(1)Er4Mg trigonal bipyramid,  an edgeedge with one O(7)Er4 tetrahedra, edges with two equivalent O(5)Er3Ta tetrahedra, and  an edgeedge with one O(1)Er4Mg trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Mg(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the third O site, O(3) is bonded to one Er(1), one Er(2), one Er(4), and one Ta(1) atom to form OEr3Ta tetrahedra that share corners with two equivalent O(3)Er3Ta tetrahedra, corners with two equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(1)Er4Mg trigonal bipyramids, edges with two equivalent O(5)Er3Ta tetrahedra, and edges with two equivalent O(7)Er4 tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Er(1), one Er(4), one Ta(1), and one Ta(2) atom. In the fifth O site, O(5) is bonded to one Er(1), one Er(2), one Er(4), and one Ta(1) atom to form distorted OEr3Ta tetrahedra that share corners with two equivalent O(3)Er3Ta tetrahedra, corners with two equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(7)Er4 tetrahedra, edges with two equivalent O(3)Er3Ta tetrahedra, and edges with two equivalent O(1)Er4Mg trigonal bipyramids. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Mg(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the seventh O site, O(7) is bonded to one Er(1), one Er(2), one Er(3), and one Er(4) atom to form OEr4 tetrahedra that share corners with two equivalent O(7)Er4 tetrahedra, corners with four equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(1)Er4Mg trigonal bipyramids, edges with two equivalent O(3)Er3Ta tetrahedra, and  an edgeedge with one O(1)Er4Mg trigonal bipyramid. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er6MgTa2O14
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.434
_cell_length_b   6.434
_cell_length_c   7.731
_cell_angle_alpha   89.178
_cell_angle_beta   89.178
_cell_angle_gamma   109.654
_symmetry_Int_Tables_number   1
_cell_volume   301.257
_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  0.032  0.510  0.213  1.0
  Er  Er1  1  0.993  0.007  0.000  1.0
  Er  Er2  1  0.961  0.039  0.500  1.0
  Er  Er3  1  0.490  0.968  0.787  1.0
  Er  Er4  1  0.512  0.062  0.231  1.0
  Er  Er5  1  0.938  0.488  0.769  1.0
  Mg  Mg6  1  0.235  0.765  0.500  1.0
  Ta  Ta7  1  0.481  0.519  0.000  1.0
  Ta  Ta8  1  0.522  0.478  0.500  1.0
  O  O9  1  0.122  0.845  0.720  1.0
  O  O10  1  0.155  0.878  0.280  1.0
  O  O11  1  0.184  0.441  0.522  1.0
  O  O12  1  0.140  0.381  0.972  1.0
  O  O13  1  0.619  0.860  0.028  1.0
  O  O14  1  0.559  0.816  0.478  1.0
  O  O15  1  0.466  0.425  0.250  1.0
  O  O16  1  0.575  0.534  0.750  1.0
  O  O17  1  0.411  0.165  0.979  1.0
  O  O18  1  0.434  0.159  0.527  1.0
  O  O19  1  0.835  0.589  0.021  1.0
  O  O20  1  0.841  0.566  0.473  1.0
  O  O21  1  0.845  0.122  0.747  1.0
  O  O22  1  0.878  0.155  0.253  1.0
[/CIF]
.
The structure described by MgEr6Ta2O14 crystallizes in the monoclinic C2 space group. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. There are four inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. In the second Er site, Er(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms. In the third Er site, Er(3) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms. In the fourth Er site, Er(4) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted ErO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O6 octahedra,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-55°. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 26°. In the second Ta site, Ta(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Er(4)O7 pentagonal bipyramids, and edges with two equivalent Er(4)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 26°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Er(1), one Er(2), one Er(3), and one Er(4) atom to form distorted OEr4Mg trigonal bipyramids that share corners with four equivalent O(3)Er3Ta tetrahedra, corners with four equivalent O(7)Er4 tetrahedra,  a cornercorner with one O(1)Er4Mg trigonal bipyramid,  an edgeedge with one O(7)Er4 tetrahedra, edges with two equivalent O(5)Er3Ta tetrahedra, and  an edgeedge with one O(1)Er4Mg trigonal bipyramid. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Mg(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the third O site, O(3) is bonded to one Er(1), one Er(2), one Er(4), and one Ta(1) atom to form OEr3Ta tetrahedra that share corners with two equivalent O(3)Er3Ta tetrahedra, corners with two equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(1)Er4Mg trigonal bipyramids, edges with two equivalent O(5)Er3Ta tetrahedra, and edges with two equivalent O(7)Er4 tetrahedra. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Er(1), one Er(4), one Ta(1), and one Ta(2) atom. In the fifth O site, O(5) is bonded to one Er(1), one Er(2), one Er(4), and one Ta(1) atom to form distorted OEr3Ta tetrahedra that share corners with two equivalent O(3)Er3Ta tetrahedra, corners with two equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(7)Er4 tetrahedra, edges with two equivalent O(3)Er3Ta tetrahedra, and edges with two equivalent O(1)Er4Mg trigonal bipyramids. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Mg(1), one Er(1), one Er(3), one Er(4), and one Ta(2) atom. In the seventh O site, O(7) is bonded to one Er(1), one Er(2), one Er(3), and one Er(4) atom to form OEr4 tetrahedra that share corners with two equivalent O(7)Er4 tetrahedra, corners with four equivalent O(5)Er3Ta tetrahedra, corners with four equivalent O(1)Er4Mg trigonal bipyramids, edges with two equivalent O(3)Er3Ta tetrahedra, and  an edgeedge with one O(1)Er4Mg trigonal bipyramid. is represented by the Crystallographic Information File (CIF) [CIF]
data_Er6MgTa2O14
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.434
_cell_length_b   6.434
_cell_length_c   7.731
_cell_angle_alpha   89.178
_cell_angle_beta   89.178
_cell_angle_gamma   109.654
_symmetry_Int_Tables_number   1
_cell_volume   301.257
_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  0.032  0.510  0.213  1.0
  Er  Er1  1  0.993  0.007  0.000  1.0
  Er  Er2  1  0.961  0.039  0.500  1.0
  Er  Er3  1  0.490  0.968  0.787  1.0
  Er  Er4  1  0.512  0.062  0.231  1.0
  Er  Er5  1  0.938  0.488  0.769  1.0
  Mg  Mg6  1  0.235  0.765  0.500  1.0
  Ta  Ta7  1  0.481  0.519  0.000  1.0
  Ta  Ta8  1  0.522  0.478  0.500  1.0
  O  O9  1  0.122  0.845  0.720  1.0
  O  O10  1  0.155  0.878  0.280  1.0
  O  O11  1  0.184  0.441  0.522  1.0
  O  O12  1  0.140  0.381  0.972  1.0
  O  O13  1  0.619  0.860  0.028  1.0
  O  O14  1  0.559  0.816  0.478  1.0
  O  O15  1  0.466  0.425  0.250  1.0
  O  O16  1  0.575  0.534  0.750  1.0
  O  O17  1  0.411  0.165  0.979  1.0
  O  O18  1  0.434  0.159  0.527  1.0
  O  O19  1  0.835  0.589  0.021  1.0
  O  O20  1  0.841  0.566  0.473  1.0
  O  O21  1  0.845  0.122  0.747  1.0
  O  O22  1  0.878  0.155  0.253  1.0
[/CIF]
.