data_YMgSi2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.23
_cell_length_b   5.23
_cell_length_c   5.23
_cell_angle_alpha   132.32
_cell_angle_beta   132.32
_cell_angle_gamma   69.72
_symmetry_Int_Tables_number   1
_chemical_formula_structural   YMgSi2
_chemical_formula_sum   'Y1 Mg1 Si2'
_cell_volume   76.83
_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
  Y  Y3  1  0.0  0.0  0.29  1.0
  Mg  Mg0  1  0.0  0.0  0.0  1.0
  Si  Si1  1  0.0  0.12  0.15  1.0
  Si  Si2  1  0.12  0.0  0.15  1.0

data_YMgSi2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   5.98
_cell_length_b   5.98
_cell_length_c   5.23
_cell_angle_alpha   90.0
_cell_angle_beta   124.86
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   YMgSi2
_chemical_formula_sum   'Y2 Mg2 Si4'
_cell_volume   153.67
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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
  Y  Y0  2  0.21  0.5  0.71  1.0
  Mg  Mg1  2  0.0  0.0  0.0  1.0
  Si  Si2  4  0.41  0.44  0.97  1.0

Y Mg Si Si
Y Mg Si Si 0 2 o o o 0 3 o o o 1 2 o o o 1 3 o o o 2 3 o o o 
MgYSi2 crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two MgYSi2 clusters. Mg(1) is bonded in a 2-coordinate geometry to two equivalent Si(1) atoms. Both Mg(1)-Si(1) bond lengths are 0.57 Å. Y(1) is bonded in a 2-coordinate geometry to two equivalent Si(1) atoms. Both Y(1)-Si(1) bond lengths are 1.26 Å. Si(1) is bonded in a 3-coordinate geometry to one Mg(1), one Y(1), and one Si(1) atom. The Si(1)-Si(1) bond length is 0.69 Å.