data_SrMgSi
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.96
_cell_length_b   4.96
_cell_length_c   4.96
_cell_angle_alpha   60.0
_cell_angle_beta   60.0
_cell_angle_gamma   60.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   SrMgSi
_chemical_formula_sum   'Sr1 Mg1 Si1'
_cell_volume   86.13
_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
  Sr  Sr2  1  0.51  0.51  0.51  1.0
  Mg  Mg0  1  0.0  0.0  0.0  1.0
  Si  Si1  1  0.75  0.75  0.75  1.0

data_SrMgSi
_symmetry_space_group_name_H-M   R3m
_cell_length_a   4.96
_cell_length_b   4.96
_cell_length_c   12.14
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   160
_chemical_formula_structural   SrMgSi
_chemical_formula_sum   'Sr3 Mg3 Si3'
_cell_volume   258.39
_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
  Sr  Sr0  3  0.0  0.0  0.49  1.0
  Mg  Mg1  3  0.0  0.0  0.0  1.0
  Si  Si2  3  0.0  0.0  0.25  1.0

Sr Mg Si
Sr Mg Si 0 1 o o + 0 1 o + o 0 1 o + + 0 1 + o o 0 1 + o + 0 1 + + o 0 2 o - o 0 2 - o o 0 2 o o - 0 2 o o o 1 2 - - - 1 2 - - o 1 2 o - - 1 2 - o - 
MgSrSi is half-Heusler structured and crystallizes in the trigonal R3m space group. Sr(1) is bonded to six equivalent Mg(1) and four equivalent Si(1) atoms to form distorted SrMg6Si4 tetrahedra that share corners with four equivalent Mg(1)Sr6Si4 tetrahedra, corners with six equivalent Sr(1)Mg6Si4 tetrahedra, edges with six equivalent Mg(1)Sr6Si4 tetrahedra, and faces with twelve equivalent Sr(1)Mg6Si4 tetrahedra. There are three shorter (3.47 Å) and three longer (3.54 Å) Sr(1)-Mg(1) bond lengths. There is one shorter (3.00 Å) and three longer (3.05 Å) Sr(1)-Si(1) bond lengths. Mg(1) is bonded to six equivalent Sr(1) and four equivalent Si(1) atoms to form distorted MgSr6Si4 tetrahedra that share corners with four equivalent Sr(1)Mg6Si4 tetrahedra, corners with six equivalent Mg(1)Sr6Si4 tetrahedra, edges with six equivalent Sr(1)Mg6Si4 tetrahedra, and faces with twelve equivalent Mg(1)Sr6Si4 tetrahedra. There is one shorter (3.00 Å) and three longer (3.05 Å) Mg(1)-Si(1) bond lengths. Si(1) is bonded in a body-centered cubic geometry to four equivalent Sr(1) and four equivalent Mg(1) atoms.