The material described by MgCr4(PbO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(14), one O(3), one O(6), and one O(8) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one Cr(2)O4 tetrahedra,  a cornercorner with one Cr(3)O4 tetrahedra, and  an edgeedge with one Cr(4)O4 tetrahedra. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a tetrahedral geometry to one O(1), one O(12), one O(16), and one O(5) atom. In the second Cr site, Cr(2) is bonded to one O(13), one O(4), one O(8), and one O(9) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra. In the third Cr site, Cr(3) is bonded to one O(11), one O(15), one O(2), and one O(6) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra. In the fourth Cr site, Cr(4) is bonded to one O(10), one O(14), one O(3), and one O(7) atom to form CrO4 tetrahedra that share  an edgeedge with one Mg(1)O4 tetrahedra. There are four inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 5-coordinate geometry to one O(12), one O(15), one O(4), one O(5), and one O(7) atom. In the second Pb site, Pb(2) is bonded in a distorted rectangular see-saw-like geometry to one O(11), one O(14), one O(16), and one O(2) atom. In the third Pb site, Pb(3) is bonded in a 5-coordinate geometry to one O(10), one O(13), one O(15), one O(3), and one O(7) atom. In the fourth Pb site, Pb(4) is bonded in a 4-coordinate geometry to one O(1), one O(10), one O(13), and one O(9) atom. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(4) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Cr(3) and one Pb(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(4), and one Pb(3) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Cr(2) and one Pb(1) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(3) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Cr(4), one Pb(1), and one Pb(3) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Mg(1) and one Cr(2) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one Cr(2) and one Pb(4) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Cr(4), one Pb(3), and one Pb(4) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to one Cr(3) and one Pb(2) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(1) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Cr(2), one Pb(3), and one Pb(4) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(4), and one Pb(2) atom. In the fifteenth O site, O(15) is bonded in a single-bond geometry to one Cr(3), one Pb(1), and one Pb(3) atom. In the sixteenth O site, O(16) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one Pb(2) atom. is represented by the CIF file [CIF]
data_MgCr4(PbO4)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.016
_cell_length_b   7.469
_cell_length_c   8.154
_cell_angle_alpha   92.556
_cell_angle_beta   90.727
_cell_angle_gamma   104.221
_symmetry_Int_Tables_number   1
_cell_volume   413.667
_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  0.574  0.129  0.897  1.0
  Cr  Cr1  1  0.393  0.699  0.330  1.0
  Cr  Cr2  1  0.882  0.216  0.178  1.0
  Cr  Cr3  1  0.123  0.803  0.828  1.0
  Cr  Cr4  1  0.619  0.330  0.628  1.0
  Pb  Pb5  1  0.906  0.689  0.365  1.0
  Pb  Pb6  1  0.586  0.695  0.898  1.0
  Pb  Pb7  1  0.060  0.251  0.622  1.0
  Pb  Pb8  1  0.327  0.207  0.219  1.0
  O  O9  1  0.316  0.888  0.295  1.0
  O  O10  1  0.224  0.630  0.778  1.0
  O  O11  1  0.699  0.133  0.678  1.0
  O  O12  1  0.768  0.381  0.246  1.0
  O  O13  1  0.195  0.544  0.392  1.0
  O  O14  1  0.306  0.973  0.918  1.0
  O  O15  1  0.832  0.485  0.586  1.0
  O  O16  1  0.699  0.041  0.079  1.0
  O  O17  1  0.060  0.277  0.040  1.0
  O  O18  1  0.412  0.274  0.509  1.0
  O  O19  1  0.942  0.735  0.959  1.0
  O  O20  1  0.573  0.737  0.469  1.0
  O  O21  1  0.008  0.138  0.344  1.0
  O  O22  1  0.549  0.379  0.832  1.0
  O  O23  1  0.038  0.884  0.662  1.0
  O  O24  1  0.475  0.610  0.157  1.0
[/CIF]
.
The material described by MgCr4(PbO4)4 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(14), one O(3), one O(6), and one O(8) atom to form distorted MgO4 tetrahedra that share  a cornercorner with one Cr(2)O4 tetrahedra,  a cornercorner with one Cr(3)O4 tetrahedra, and  an edgeedge with one Cr(4)O4 tetrahedra. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded in a tetrahedral geometry to one O(1), one O(12), one O(16), and one O(5) atom. In the second Cr site, Cr(2) is bonded to one O(13), one O(4), one O(8), and one O(9) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra. In the third Cr site, Cr(3) is bonded to one O(11), one O(15), one O(2), and one O(6) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O4 tetrahedra. In the fourth Cr site, Cr(4) is bonded to one O(10), one O(14), one O(3), and one O(7) atom to form CrO4 tetrahedra that share  an edgeedge with one Mg(1)O4 tetrahedra. There are four inequivalent Pb sites. In the first Pb site, Pb(1) is bonded in a 5-coordinate geometry to one O(12), one O(15), one O(4), one O(5), and one O(7) atom. In the second Pb site, Pb(2) is bonded in a distorted rectangular see-saw-like geometry to one O(11), one O(14), one O(16), and one O(2) atom. In the third Pb site, Pb(3) is bonded in a 5-coordinate geometry to one O(10), one O(13), one O(15), one O(3), and one O(7) atom. In the fourth Pb site, Pb(4) is bonded in a 4-coordinate geometry to one O(1), one O(10), one O(13), and one O(9) atom. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(4) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Cr(3) and one Pb(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(4), and one Pb(3) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Cr(2) and one Pb(1) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(3) atom. In the seventh O site, O(7) is bonded in a distorted single-bond geometry to one Cr(4), one Pb(1), and one Pb(3) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Mg(1) and one Cr(2) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one Cr(2) and one Pb(4) atom. In the tenth O site, O(10) is bonded in a distorted single-bond geometry to one Cr(4), one Pb(3), and one Pb(4) atom. In the eleventh O site, O(11) is bonded in a distorted bent 120 degrees geometry to one Cr(3) and one Pb(2) atom. In the twelfth O site, O(12) is bonded in a distorted single-bond geometry to one Cr(1) and one Pb(1) atom. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Cr(2), one Pb(3), and one Pb(4) atom. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Mg(1), one Cr(4), and one Pb(2) atom. In the fifteenth O site, O(15) is bonded in a single-bond geometry to one Cr(3), one Pb(1), and one Pb(3) atom. In the sixteenth O site, O(16) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and one Pb(2) atom. is represented by the CIF file [CIF]
data_MgCr4(PbO4)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.016
_cell_length_b   7.469
_cell_length_c   8.154
_cell_angle_alpha   92.556
_cell_angle_beta   90.727
_cell_angle_gamma   104.221
_symmetry_Int_Tables_number   1
_cell_volume   413.667
_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  0.574  0.129  0.897  1.0
  Cr  Cr1  1  0.393  0.699  0.330  1.0
  Cr  Cr2  1  0.882  0.216  0.178  1.0
  Cr  Cr3  1  0.123  0.803  0.828  1.0
  Cr  Cr4  1  0.619  0.330  0.628  1.0
  Pb  Pb5  1  0.906  0.689  0.365  1.0
  Pb  Pb6  1  0.586  0.695  0.898  1.0
  Pb  Pb7  1  0.060  0.251  0.622  1.0
  Pb  Pb8  1  0.327  0.207  0.219  1.0
  O  O9  1  0.316  0.888  0.295  1.0
  O  O10  1  0.224  0.630  0.778  1.0
  O  O11  1  0.699  0.133  0.678  1.0
  O  O12  1  0.768  0.381  0.246  1.0
  O  O13  1  0.195  0.544  0.392  1.0
  O  O14  1  0.306  0.973  0.918  1.0
  O  O15  1  0.832  0.485  0.586  1.0
  O  O16  1  0.699  0.041  0.079  1.0
  O  O17  1  0.060  0.277  0.040  1.0
  O  O18  1  0.412  0.274  0.509  1.0
  O  O19  1  0.942  0.735  0.959  1.0
  O  O20  1  0.573  0.737  0.469  1.0
  O  O21  1  0.008  0.138  0.344  1.0
  O  O22  1  0.549  0.379  0.832  1.0
  O  O23  1  0.038  0.884  0.662  1.0
  O  O24  1  0.475  0.610  0.157  1.0
[/CIF]
.