The compound described by Mg3W3As4O16 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(3), one O(4), and one O(5) atom to form MgO4 trigonal pyramids that share corners with two equivalent W(1)O5 trigonal bipyramids. 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 edges with two equivalent W(1)O5 trigonal bipyramids. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(4), one O(7), and one O(8) atom to form WO5 trigonal bipyramids that share corners with two equivalent Mg(1)O4 trigonal pyramids and  an edgeedge with one Mg(2)O6 octahedra. In the second W site, W(2) is bonded in a square co-planar geometry to 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 in a distorted trigonal non-coplanar geometry to one O(3), one O(6), and one O(8) atom. In the second As site, As(2) is bonded in a water-like geometry to one O(2) and one O(3) atom. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a bent 150 degrees geometry to one W(1) and one W(2) atom. In the second O site, O(8) is bonded in a trigonal planar geometry to one Mg(2), one W(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(2), one W(1), and one As(2) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to one Mg(1), one As(1), and one As(2) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one As(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3As4W3O16
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.564
_cell_length_b   10.141
_cell_length_c   15.891
_cell_angle_alpha   74.143
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   862.586
_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  0.377  0.294  0.219  1.0
  Mg  Mg1  1  0.877  0.706  0.281  1.0
  Mg  Mg2  1  0.623  0.706  0.781  1.0
  Mg  Mg3  1  0.123  0.294  0.719  1.0
  Mg  Mg4  1  0.500  0.000  0.500  1.0
  Mg  Mg5  1  0.000  0.000  0.000  1.0
  As  As6  1  0.981  0.108  0.346  1.0
  As  As7  1  0.330  0.344  0.422  1.0
  As  As8  1  0.830  0.656  0.078  1.0
  As  As9  1  0.170  0.344  0.922  1.0
  As  As10  1  0.019  0.892  0.654  1.0
  As  As11  1  0.670  0.656  0.578  1.0
  As  As12  1  0.519  0.108  0.846  1.0
  As  As13  1  0.481  0.892  0.154  1.0
  W  W14  1  0.622  0.195  0.615  1.0
  W  W15  1  0.378  0.805  0.385  1.0
  W  W16  1  0.122  0.805  0.885  1.0
  W  W17  1  0.878  0.195  0.115  1.0
  W  W18  1  0.000  0.500  0.500  1.0
  W  W19  1  0.500  0.500  0.000  1.0
  O  O20  1  0.180  0.797  0.294  1.0
  O  O21  1  0.889  0.810  0.993  1.0
  O  O22  1  0.196  0.266  0.337  1.0
  O  O23  1  0.154  0.179  0.177  1.0
  O  O24  1  0.804  0.734  0.663  1.0
  O  O25  1  0.320  0.797  0.794  1.0
  O  O26  1  0.696  0.734  0.163  1.0
  O  O27  1  0.618  0.552  0.885  1.0
  O  O28  1  0.703  0.111  0.929  1.0
  O  O29  1  0.820  0.203  0.706  1.0
  O  O30  1  0.346  0.179  0.677  1.0
  O  O31  1  0.382  0.448  0.115  1.0
  O  O32  1  0.281  0.638  0.461  1.0
  O  O33  1  0.297  0.889  0.071  1.0
  O  O34  1  0.712  0.022  0.605  1.0
  O  O35  1  0.212  0.978  0.895  1.0
  O  O36  1  0.781  0.362  0.039  1.0
  O  O37  1  0.304  0.266  0.837  1.0
  O  O38  1  0.203  0.889  0.571  1.0
  O  O39  1  0.118  0.448  0.615  1.0
  O  O40  1  0.788  0.022  0.105  1.0
  O  O41  1  0.288  0.978  0.395  1.0
  O  O42  1  0.111  0.190  0.007  1.0
  O  O43  1  0.389  0.190  0.507  1.0
  O  O44  1  0.719  0.362  0.539  1.0
  O  O45  1  0.680  0.203  0.206  1.0
  O  O46  1  0.846  0.821  0.823  1.0
  O  O47  1  0.797  0.111  0.429  1.0
  O  O48  1  0.611  0.810  0.493  1.0
  O  O49  1  0.882  0.552  0.385  1.0
  O  O50  1  0.219  0.638  0.961  1.0
  O  O51  1  0.654  0.821  0.323  1.0
[/CIF]
.
The compound described by Mg3W3As4O16 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(3), one O(4), and one O(5) atom to form MgO4 trigonal pyramids that share corners with two equivalent W(1)O5 trigonal bipyramids. 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 edges with two equivalent W(1)O5 trigonal bipyramids. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(4), one O(7), and one O(8) atom to form WO5 trigonal bipyramids that share corners with two equivalent Mg(1)O4 trigonal pyramids and  an edgeedge with one Mg(2)O6 octahedra. In the second W site, W(2) is bonded in a square co-planar geometry to 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 in a distorted trigonal non-coplanar geometry to one O(3), one O(6), and one O(8) atom. In the second As site, As(2) is bonded in a water-like geometry to one O(2) and one O(3) atom. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a bent 150 degrees geometry to one W(1) and one W(2) atom. In the second O site, O(8) is bonded in a trigonal planar geometry to one Mg(2), one W(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(2), one W(1), and one As(2) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to one Mg(1), one As(1), and one As(2) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one As(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg3As4W3O16
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.564
_cell_length_b   10.141
_cell_length_c   15.891
_cell_angle_alpha   74.143
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   862.586
_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  0.377  0.294  0.219  1.0
  Mg  Mg1  1  0.877  0.706  0.281  1.0
  Mg  Mg2  1  0.623  0.706  0.781  1.0
  Mg  Mg3  1  0.123  0.294  0.719  1.0
  Mg  Mg4  1  0.500  0.000  0.500  1.0
  Mg  Mg5  1  0.000  0.000  0.000  1.0
  As  As6  1  0.981  0.108  0.346  1.0
  As  As7  1  0.330  0.344  0.422  1.0
  As  As8  1  0.830  0.656  0.078  1.0
  As  As9  1  0.170  0.344  0.922  1.0
  As  As10  1  0.019  0.892  0.654  1.0
  As  As11  1  0.670  0.656  0.578  1.0
  As  As12  1  0.519  0.108  0.846  1.0
  As  As13  1  0.481  0.892  0.154  1.0
  W  W14  1  0.622  0.195  0.615  1.0
  W  W15  1  0.378  0.805  0.385  1.0
  W  W16  1  0.122  0.805  0.885  1.0
  W  W17  1  0.878  0.195  0.115  1.0
  W  W18  1  0.000  0.500  0.500  1.0
  W  W19  1  0.500  0.500  0.000  1.0
  O  O20  1  0.180  0.797  0.294  1.0
  O  O21  1  0.889  0.810  0.993  1.0
  O  O22  1  0.196  0.266  0.337  1.0
  O  O23  1  0.154  0.179  0.177  1.0
  O  O24  1  0.804  0.734  0.663  1.0
  O  O25  1  0.320  0.797  0.794  1.0
  O  O26  1  0.696  0.734  0.163  1.0
  O  O27  1  0.618  0.552  0.885  1.0
  O  O28  1  0.703  0.111  0.929  1.0
  O  O29  1  0.820  0.203  0.706  1.0
  O  O30  1  0.346  0.179  0.677  1.0
  O  O31  1  0.382  0.448  0.115  1.0
  O  O32  1  0.281  0.638  0.461  1.0
  O  O33  1  0.297  0.889  0.071  1.0
  O  O34  1  0.712  0.022  0.605  1.0
  O  O35  1  0.212  0.978  0.895  1.0
  O  O36  1  0.781  0.362  0.039  1.0
  O  O37  1  0.304  0.266  0.837  1.0
  O  O38  1  0.203  0.889  0.571  1.0
  O  O39  1  0.118  0.448  0.615  1.0
  O  O40  1  0.788  0.022  0.105  1.0
  O  O41  1  0.288  0.978  0.395  1.0
  O  O42  1  0.111  0.190  0.007  1.0
  O  O43  1  0.389  0.190  0.507  1.0
  O  O44  1  0.719  0.362  0.539  1.0
  O  O45  1  0.680  0.203  0.206  1.0
  O  O46  1  0.846  0.821  0.823  1.0
  O  O47  1  0.797  0.111  0.429  1.0
  O  O48  1  0.611  0.810  0.493  1.0
  O  O49  1  0.882  0.552  0.385  1.0
  O  O50  1  0.219  0.638  0.961  1.0
  O  O51  1  0.654  0.821  0.323  1.0
[/CIF]
.