The structure described by Mg3Ti3(AsO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(4), one O(5), one O(7), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra and edges with two equivalent Ti(1)O6 octahedra. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(8) atom to form distorted TiO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(5), and two equivalent O(7) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(2)O6 octahedra, and corners with three equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-67°. In the second As site, As(2) is bonded in a 3-coordinate geometry to one O(3), one O(5), and one O(7) atom. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Ti(1), one Ti(2), and one As(2) atom. In the second O site, O(8) is bonded in a distorted T-shaped geometry to one Mg(2), one Ti(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one As(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to one Mg(2), one Ti(1), and one Ti(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one As(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ti(1), and one As(1) atom. In the seventh O site, O(5) is bonded to one Mg(1), one Ti(1), one Ti(2), and one As(2) atom to form corner-sharing OMgTi2As tetrahedra. In the eighth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mg(2) and one As(1) atom. is represented by the CIF file [CIF]
data_Mg3Ti3(AsO4)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.027
_cell_length_b   8.140
_cell_length_c   16.519
_cell_angle_alpha   74.869
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   652.547
_cell_formula_units_Z   2
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  0.590  0.361  0.208  1.0
  Mg  Mg1  1  0.090  0.639  0.292  1.0
  Mg  Mg2  1  0.410  0.639  0.792  1.0
  Mg  Mg3  1  0.910  0.361  0.708  1.0
  Mg  Mg4  1  0.500  0.000  0.500  1.0
  Mg  Mg5  1  0.000  0.000  0.000  1.0
  Ti  Ti6  1  0.431  0.228  0.622  1.0
  Ti  Ti7  1  0.569  0.772  0.378  1.0
  Ti  Ti8  1  0.931  0.772  0.878  1.0
  Ti  Ti9  1  0.069  0.228  0.122  1.0
  Ti  Ti10  1  0.000  0.500  0.500  1.0
  Ti  Ti11  1  0.500  0.500  0.000  1.0
  As  As12  1  0.998  0.059  0.342  1.0
  As  As13  1  0.513  0.395  0.395  1.0
  As  As14  1  0.013  0.605  0.105  1.0
  As  As15  1  0.987  0.395  0.895  1.0
  As  As16  1  0.002  0.941  0.658  1.0
  As  As17  1  0.487  0.605  0.605  1.0
  As  As18  1  0.502  0.059  0.842  1.0
  As  As19  1  0.498  0.941  0.158  1.0
  O  O20  1  0.431  0.790  0.253  1.0
  O  O21  1  0.808  0.788  0.975  1.0
  O  O22  1  0.372  0.428  0.296  1.0
  O  O23  1  0.387  0.123  0.186  1.0
  O  O24  1  0.628  0.572  0.704  1.0
  O  O25  1  0.069  0.790  0.753  1.0
  O  O26  1  0.872  0.572  0.204  1.0
  O  O27  1  0.710  0.556  0.882  1.0
  O  O28  1  0.683  0.129  0.914  1.0
  O  O29  1  0.569  0.210  0.747  1.0
  O  O30  1  0.113  0.123  0.686  1.0
  O  O31  1  0.290  0.444  0.118  1.0
  O  O32  1  0.293  0.592  0.415  1.0
  O  O33  1  0.317  0.871  0.086  1.0
  O  O34  1  0.684  0.005  0.620  1.0
  O  O35  1  0.184  0.995  0.880  1.0
  O  O36  1  0.793  0.408  0.085  1.0
  O  O37  1  0.128  0.428  0.796  1.0
  O  O38  1  0.183  0.871  0.586  1.0
  O  O39  1  0.210  0.444  0.618  1.0
  O  O40  1  0.816  0.005  0.120  1.0
  O  O41  1  0.316  0.995  0.380  1.0
  O  O42  1  0.192  0.212  0.025  1.0
  O  O43  1  0.308  0.212  0.525  1.0
  O  O44  1  0.707  0.408  0.585  1.0
  O  O45  1  0.931  0.210  0.247  1.0
  O  O46  1  0.613  0.877  0.814  1.0
  O  O47  1  0.817  0.129  0.414  1.0
  O  O48  1  0.692  0.788  0.475  1.0
  O  O49  1  0.790  0.556  0.382  1.0
  O  O50  1  0.207  0.592  0.915  1.0
  O  O51  1  0.887  0.877  0.314  1.0
[/CIF]
.
The structure described by Mg3Ti3(AsO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(4), one O(5), one O(7), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent As(1)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra and edges with two equivalent Ti(1)O6 octahedra. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(8) atom to form distorted TiO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(5), and two equivalent O(7) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent Mg(2)O6 octahedra, and corners with three equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-67°. In the second As site, As(2) is bonded in a 3-coordinate geometry to one O(3), one O(5), and one O(7) atom. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a rectangular see-saw-like geometry to one Mg(1), one Ti(1), one Ti(2), and one As(2) atom. In the second O site, O(8) is bonded in a distorted T-shaped geometry to one Mg(2), one Ti(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one As(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to one Mg(2), one Ti(1), and one Ti(2) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one As(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ti(1), and one As(1) atom. In the seventh O site, O(5) is bonded to one Mg(1), one Ti(1), one Ti(2), and one As(2) atom to form corner-sharing OMgTi2As tetrahedra. In the eighth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mg(2) and one As(1) atom. is represented by the CIF file [CIF]
data_Mg3Ti3(AsO4)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.027
_cell_length_b   8.140
_cell_length_c   16.519
_cell_angle_alpha   74.869
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   652.547
_cell_formula_units_Z   2
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  0.590  0.361  0.208  1.0
  Mg  Mg1  1  0.090  0.639  0.292  1.0
  Mg  Mg2  1  0.410  0.639  0.792  1.0
  Mg  Mg3  1  0.910  0.361  0.708  1.0
  Mg  Mg4  1  0.500  0.000  0.500  1.0
  Mg  Mg5  1  0.000  0.000  0.000  1.0
  Ti  Ti6  1  0.431  0.228  0.622  1.0
  Ti  Ti7  1  0.569  0.772  0.378  1.0
  Ti  Ti8  1  0.931  0.772  0.878  1.0
  Ti  Ti9  1  0.069  0.228  0.122  1.0
  Ti  Ti10  1  0.000  0.500  0.500  1.0
  Ti  Ti11  1  0.500  0.500  0.000  1.0
  As  As12  1  0.998  0.059  0.342  1.0
  As  As13  1  0.513  0.395  0.395  1.0
  As  As14  1  0.013  0.605  0.105  1.0
  As  As15  1  0.987  0.395  0.895  1.0
  As  As16  1  0.002  0.941  0.658  1.0
  As  As17  1  0.487  0.605  0.605  1.0
  As  As18  1  0.502  0.059  0.842  1.0
  As  As19  1  0.498  0.941  0.158  1.0
  O  O20  1  0.431  0.790  0.253  1.0
  O  O21  1  0.808  0.788  0.975  1.0
  O  O22  1  0.372  0.428  0.296  1.0
  O  O23  1  0.387  0.123  0.186  1.0
  O  O24  1  0.628  0.572  0.704  1.0
  O  O25  1  0.069  0.790  0.753  1.0
  O  O26  1  0.872  0.572  0.204  1.0
  O  O27  1  0.710  0.556  0.882  1.0
  O  O28  1  0.683  0.129  0.914  1.0
  O  O29  1  0.569  0.210  0.747  1.0
  O  O30  1  0.113  0.123  0.686  1.0
  O  O31  1  0.290  0.444  0.118  1.0
  O  O32  1  0.293  0.592  0.415  1.0
  O  O33  1  0.317  0.871  0.086  1.0
  O  O34  1  0.684  0.005  0.620  1.0
  O  O35  1  0.184  0.995  0.880  1.0
  O  O36  1  0.793  0.408  0.085  1.0
  O  O37  1  0.128  0.428  0.796  1.0
  O  O38  1  0.183  0.871  0.586  1.0
  O  O39  1  0.210  0.444  0.618  1.0
  O  O40  1  0.816  0.005  0.120  1.0
  O  O41  1  0.316  0.995  0.380  1.0
  O  O42  1  0.192  0.212  0.025  1.0
  O  O43  1  0.308  0.212  0.525  1.0
  O  O44  1  0.707  0.408  0.585  1.0
  O  O45  1  0.931  0.210  0.247  1.0
  O  O46  1  0.613  0.877  0.814  1.0
  O  O47  1  0.817  0.129  0.414  1.0
  O  O48  1  0.692  0.788  0.475  1.0
  O  O49  1  0.790  0.556  0.382  1.0
  O  O50  1  0.207  0.592  0.915  1.0
  O  O51  1  0.887  0.877  0.314  1.0
[/CIF]
.