data_Mg2SiP
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.65
_cell_length_b   4.65
_cell_length_c   4.65
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2SiP
_chemical_formula_sum   'Mg2 Si1 P1'
_cell_volume   70.97
_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  0.64  0.64  0.64  1.0
  Mg  Mg1  1  0.0  0.0  0.0  1.0
  Si  Si3  1  0.29  0.29  0.29  1.0
  P  P2  1  0.93  0.93  0.93  1.0

data_Mg2SiP
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.65
_cell_length_b   4.65
_cell_length_c   11.38
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   Mg2SiP
_chemical_formula_sum   'Mg6 Si3 P3'
_cell_volume   212.91
_cell_formula_units_Z   3
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  '-y, -x, z'
  5  '-x+y, y, z'
  6  'x, x-y, z'
  7  'x+1/3, y+2/3, z+2/3'
  8  '-y+1/3, x-y+2/3, z+2/3'
  9  '-x+y+1/3, -x+2/3, z+2/3'
  10  '-y+1/3, -x+2/3, z+2/3'
  11  '-x+y+1/3, y+2/3, z+2/3'
  12  'x+1/3, x-y+2/3, z+2/3'
  13  'x+2/3, y+1/3, z+1/3'
  14  '-y+2/3, x-y+1/3, z+1/3'
  15  '-x+y+2/3, -x+1/3, z+1/3'
  16  '-y+2/3, -x+1/3, z+1/3'
  17  '-x+y+2/3, y+1/3, z+1/3'
  18  'x+2/3, x-y+1/3, z+1/3'
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  3  0.0  0.0  0.0  1.0
  Mg  Mg1  3  0.0  0.0  0.36  1.0
  Si  Si2  3  0.0  0.0  0.71  1.0
  P  P3  3  0.0  0.0  0.07  1.0

Mg Mg Si P
Mg2SiP crystallizes in the trigonal R3m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 10-coordinate geometry to three equivalent Mg(2), three equivalent Si(1), and four equivalent P(1) atoms. All Mg(1)-Mg(2) bond lengths are 2.70 Å. All Mg(1)-Si(1) bond lengths are 2.70 Å. There are three shorter (2.74 Å) and one longer (3.26 Å) Mg(1)-P(1) bond length. In the second Mg site, Mg(2) is bonded in a single-bond geometry to three equivalent Mg(1), four equivalent Si(1), and one P(1) atom. There are three shorter (2.74 Å) and one longer (3.26 Å) Mg(2)-Si(1) bond length. The Mg(2)-P(1) bond length is 0.81 Å. Si(1) is bonded in a 10-coordinate geometry to three equivalent Mg(1), four equivalent Mg(2), and three equivalent P(1) atoms. All Si(1)-P(1) bond lengths are 2.70 Å. P(1) is bonded in a single-bond geometry to one Mg(2), four equivalent Mg(1), and three equivalent Si(1) atoms.