The compound described by Mg2Ta3N5 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(1) and four equivalent N(2) atoms to form MgN6 octahedra that share corners with two equivalent Mg(2)N6 octahedra, corners with two equivalent Ta(1)N6 octahedra, corners with two equivalent Ta(3)N6 octahedra,  an edgeedge with one Mg(2)N6 octahedra, edges with two equivalent Mg(1)N6 octahedra, edges with two equivalent Ta(1)N6 octahedra, edges with three equivalent Ta(2)N6 octahedra, and edges with four equivalent Ta(3)N6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the second Mg site, Mg(2) is bonded to two equivalent N(3) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(1)N6 octahedra, corners with two equivalent Mg(2)N6 octahedra, corners with two equivalent Ta(3)N6 octahedra,  an edgeedge with one Mg(1)N6 octahedra,  an edgeedge with one Ta(3)N6 octahedra, edges with two equivalent Mg(2)N6 octahedra, edges with four equivalent Ta(1)N6 octahedra, and edges with four equivalent Ta(2)N6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. There are three inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent N(1), two equivalent N(2), and two equivalent N(3) atoms to form TaN6 octahedra that share corners with two equivalent Mg(1)N6 octahedra, corners with two equivalent Ta(1)N6 octahedra, corners with two equivalent Ta(2)N6 octahedra, edges with two equivalent Mg(1)N6 octahedra, edges with three equivalent Ta(2)N6 octahedra, edges with three equivalent Ta(3)N6 octahedra, and edges with four equivalent Mg(2)N6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second Ta site, Ta(2) is bonded to two equivalent N(1), two equivalent N(2), and two equivalent N(3) atoms to form TaN6 octahedra that share corners with two equivalent Ta(1)N6 octahedra, corners with two equivalent Ta(2)N6 octahedra, corners with two equivalent Ta(3)N6 octahedra, edges with two equivalent Ta(3)N6 octahedra, edges with three equivalent Mg(1)N6 octahedra, edges with three equivalent Ta(1)N6 octahedra, and edges with four equivalent Mg(2)N6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the third Ta site, Ta(3) is bonded to two equivalent N(1) and four equivalent N(2) atoms to form TaN6 octahedra that share corners with two equivalent Mg(1)N6 octahedra, corners with two equivalent Mg(2)N6 octahedra, corners with two equivalent Ta(2)N6 octahedra,  an edgeedge with one Mg(2)N6 octahedra, edges with two equivalent Ta(2)N6 octahedra, edges with two equivalent Ta(3)N6 octahedra, edges with three equivalent Ta(1)N6 octahedra, and edges with four equivalent Mg(1)N6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Mg(1), two equivalent Mg(2), one Ta(1), one Ta(2), and one Ta(3) atom to form NMg3Ta3 octahedra that share corners with two equivalent N(2)Mg2Ta4 octahedra, corners with four equivalent N(1)Mg3Ta3 octahedra, edges with three equivalent N(1)Mg3Ta3 octahedra, edges with four equivalent N(3)Mg2Ta4 octahedra, and edges with five equivalent N(2)Mg2Ta4 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. In the second N site, N(2) is bonded to two equivalent Mg(1), one Ta(1), one Ta(2), and two equivalent Ta(3) atoms to form NMg2Ta4 octahedra that share corners with two equivalent N(2)Mg2Ta4 octahedra, corners with two equivalent N(3)Mg2Ta4 octahedra, corners with two equivalent N(1)Mg3Ta3 octahedra,  an edgeedge with one N(3)Mg2Ta4 octahedra, edges with five equivalent N(1)Mg3Ta3 octahedra, and edges with six equivalent N(2)Mg2Ta4 octahedra. The corner-sharing octahedral tilt angles range from 2-4°. In the third N site, N(3) is bonded to two equivalent Mg(2), two equivalent Ta(1), and two equivalent Ta(2) atoms to form NMg2Ta4 octahedra that share corners with two equivalent N(3)Mg2Ta4 octahedra, corners with four equivalent N(2)Mg2Ta4 octahedra, edges with two equivalent N(2)Mg2Ta4 octahedra, edges with two equivalent N(3)Mg2Ta4 octahedra, and edges with eight equivalent N(1)Mg3Ta3 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Ta3N5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.200
_cell_length_b   8.200
_cell_length_c   5.319
_cell_angle_alpha   83.848
_cell_angle_beta   83.848
_cell_angle_gamma   141.851
_symmetry_Int_Tables_number   1
_cell_volume   208.687
_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  0.449  0.551  0.750  1.0
  Mg  Mg1  1  0.551  0.449  0.250  1.0
  Mg  Mg2  1  0.252  0.748  0.750  1.0
  Mg  Mg3  1  0.748  0.252  0.250  1.0
  Ta  Ta4  1  0.851  0.149  0.750  1.0
  Ta  Ta5  1  0.353  0.647  0.250  1.0
  Ta  Ta6  1  0.046  0.954  0.750  1.0
  Ta  Ta7  1  0.954  0.046  0.250  1.0
  Ta  Ta8  1  0.647  0.353  0.750  1.0
  Ta  Ta9  1  0.149  0.851  0.250  1.0
  N  N10  1  0.095  0.395  0.000  1.0
  N  N11  1  0.690  0.789  0.998  1.0
  N  N12  1  0.605  0.905  0.500  1.0
  N  N13  1  0.310  0.211  0.002  1.0
  N  N14  1  0.211  0.310  0.502  1.0
  N  N15  1  0.905  0.605  1.000  1.0
  N  N16  1  0.789  0.690  0.498  1.0
  N  N17  1  0.500  0.000  0.000  1.0
  N  N18  1  0.395  0.095  0.500  1.0
  N  N19  1  0.000  0.500  0.500  1.0
[/CIF]
.
The compound described by Mg2Ta3N5 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(1) and four equivalent N(2) atoms to form MgN6 octahedra that share corners with two equivalent Mg(2)N6 octahedra, corners with two equivalent Ta(1)N6 octahedra, corners with two equivalent Ta(3)N6 octahedra,  an edgeedge with one Mg(2)N6 octahedra, edges with two equivalent Mg(1)N6 octahedra, edges with two equivalent Ta(1)N6 octahedra, edges with three equivalent Ta(2)N6 octahedra, and edges with four equivalent Ta(3)N6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the second Mg site, Mg(2) is bonded to two equivalent N(3) and four equivalent N(1) atoms to form MgN6 octahedra that share corners with two equivalent Mg(1)N6 octahedra, corners with two equivalent Mg(2)N6 octahedra, corners with two equivalent Ta(3)N6 octahedra,  an edgeedge with one Mg(1)N6 octahedra,  an edgeedge with one Ta(3)N6 octahedra, edges with two equivalent Mg(2)N6 octahedra, edges with four equivalent Ta(1)N6 octahedra, and edges with four equivalent Ta(2)N6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. There are three inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to two equivalent N(1), two equivalent N(2), and two equivalent N(3) atoms to form TaN6 octahedra that share corners with two equivalent Mg(1)N6 octahedra, corners with two equivalent Ta(1)N6 octahedra, corners with two equivalent Ta(2)N6 octahedra, edges with two equivalent Mg(1)N6 octahedra, edges with three equivalent Ta(2)N6 octahedra, edges with three equivalent Ta(3)N6 octahedra, and edges with four equivalent Mg(2)N6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the second Ta site, Ta(2) is bonded to two equivalent N(1), two equivalent N(2), and two equivalent N(3) atoms to form TaN6 octahedra that share corners with two equivalent Ta(1)N6 octahedra, corners with two equivalent Ta(2)N6 octahedra, corners with two equivalent Ta(3)N6 octahedra, edges with two equivalent Ta(3)N6 octahedra, edges with three equivalent Mg(1)N6 octahedra, edges with three equivalent Ta(1)N6 octahedra, and edges with four equivalent Mg(2)N6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. In the third Ta site, Ta(3) is bonded to two equivalent N(1) and four equivalent N(2) atoms to form TaN6 octahedra that share corners with two equivalent Mg(1)N6 octahedra, corners with two equivalent Mg(2)N6 octahedra, corners with two equivalent Ta(2)N6 octahedra,  an edgeedge with one Mg(2)N6 octahedra, edges with two equivalent Ta(2)N6 octahedra, edges with two equivalent Ta(3)N6 octahedra, edges with three equivalent Ta(1)N6 octahedra, and edges with four equivalent Mg(1)N6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Mg(1), two equivalent Mg(2), one Ta(1), one Ta(2), and one Ta(3) atom to form NMg3Ta3 octahedra that share corners with two equivalent N(2)Mg2Ta4 octahedra, corners with four equivalent N(1)Mg3Ta3 octahedra, edges with three equivalent N(1)Mg3Ta3 octahedra, edges with four equivalent N(3)Mg2Ta4 octahedra, and edges with five equivalent N(2)Mg2Ta4 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. In the second N site, N(2) is bonded to two equivalent Mg(1), one Ta(1), one Ta(2), and two equivalent Ta(3) atoms to form NMg2Ta4 octahedra that share corners with two equivalent N(2)Mg2Ta4 octahedra, corners with two equivalent N(3)Mg2Ta4 octahedra, corners with two equivalent N(1)Mg3Ta3 octahedra,  an edgeedge with one N(3)Mg2Ta4 octahedra, edges with five equivalent N(1)Mg3Ta3 octahedra, and edges with six equivalent N(2)Mg2Ta4 octahedra. The corner-sharing octahedral tilt angles range from 2-4°. In the third N site, N(3) is bonded to two equivalent Mg(2), two equivalent Ta(1), and two equivalent Ta(2) atoms to form NMg2Ta4 octahedra that share corners with two equivalent N(3)Mg2Ta4 octahedra, corners with four equivalent N(2)Mg2Ta4 octahedra, edges with two equivalent N(2)Mg2Ta4 octahedra, edges with two equivalent N(3)Mg2Ta4 octahedra, and edges with eight equivalent N(1)Mg3Ta3 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg2Ta3N5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.200
_cell_length_b   8.200
_cell_length_c   5.319
_cell_angle_alpha   83.848
_cell_angle_beta   83.848
_cell_angle_gamma   141.851
_symmetry_Int_Tables_number   1
_cell_volume   208.687
_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  0.449  0.551  0.750  1.0
  Mg  Mg1  1  0.551  0.449  0.250  1.0
  Mg  Mg2  1  0.252  0.748  0.750  1.0
  Mg  Mg3  1  0.748  0.252  0.250  1.0
  Ta  Ta4  1  0.851  0.149  0.750  1.0
  Ta  Ta5  1  0.353  0.647  0.250  1.0
  Ta  Ta6  1  0.046  0.954  0.750  1.0
  Ta  Ta7  1  0.954  0.046  0.250  1.0
  Ta  Ta8  1  0.647  0.353  0.750  1.0
  Ta  Ta9  1  0.149  0.851  0.250  1.0
  N  N10  1  0.095  0.395  0.000  1.0
  N  N11  1  0.690  0.789  0.998  1.0
  N  N12  1  0.605  0.905  0.500  1.0
  N  N13  1  0.310  0.211  0.002  1.0
  N  N14  1  0.211  0.310  0.502  1.0
  N  N15  1  0.905  0.605  1.000  1.0
  N  N16  1  0.789  0.690  0.498  1.0
  N  N17  1  0.500  0.000  0.000  1.0
  N  N18  1  0.395  0.095  0.500  1.0
  N  N19  1  0.000  0.500  0.500  1.0
[/CIF]
.