The structure described by Mg(BH4)2 crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent H(1) and four equivalent H(2) atoms to form distorted MgH8 hexagonal bipyramids that share edges with four equivalent B(1)H4 tetrahedra. In the second Mg site, Mg(2) is bonded in a body-centered cubic geometry to eight equivalent H(3) atoms. B(1) is bonded to one H(1), one H(2), and two equivalent H(3) atoms to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. There are three inequivalent H sites. In the first H site, H(1) is bonded in an L-shaped geometry to one Mg(1) and one B(1) atom. In the second H site, H(2) is bonded in an L-shaped geometry to one Mg(1) and one B(1) atom. In the third H site, H(3) is bonded in an L-shaped geometry to one Mg(2) and one B(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg(BH4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.698
_cell_length_b   7.698
_cell_length_c   7.698
_cell_angle_alpha   115.252
_cell_angle_beta   115.252
_cell_angle_gamma   98.442
_symmetry_Int_Tables_number   1
_cell_volume   341.643
_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  0.250  0.750  0.500  1.0
  Mg  Mg1  1  0.000  0.000  0.000  1.0
  B  B2  1  0.619  0.849  0.769  1.0
  B  B3  1  0.080  0.849  0.231  1.0
  B  B4  1  0.151  0.381  0.231  1.0
  B  B5  1  0.151  0.920  0.769  1.0
  H  H6  1  0.480  0.729  0.751  1.0
  H  H7  1  0.977  0.729  0.249  1.0
  H  H8  1  0.271  0.520  0.249  1.0
  H  H9  1  0.271  0.023  0.751  1.0
  H  H10  1  0.272  0.915  0.357  1.0
  H  H11  1  0.558  0.915  0.643  1.0
  H  H12  1  0.085  0.728  0.643  1.0
  H  H13  1  0.085  0.442  0.357  1.0
  H  H14  1  0.718  0.002  0.967  1.0
  H  H15  1  0.035  0.751  0.033  1.0
  H  H16  1  0.035  0.002  0.284  1.0
  H  H17  1  0.718  0.751  0.716  1.0
  H  H18  1  0.249  0.282  0.284  1.0
  H  H19  1  0.998  0.965  0.716  1.0
  H  H20  1  0.249  0.965  0.967  1.0
  H  H21  1  0.998  0.282  0.033  1.0
[/CIF]
.
The structure described by Mg(BH4)2 crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent H(1) and four equivalent H(2) atoms to form distorted MgH8 hexagonal bipyramids that share edges with four equivalent B(1)H4 tetrahedra. In the second Mg site, Mg(2) is bonded in a body-centered cubic geometry to eight equivalent H(3) atoms. B(1) is bonded to one H(1), one H(2), and two equivalent H(3) atoms to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. There are three inequivalent H sites. In the first H site, H(1) is bonded in an L-shaped geometry to one Mg(1) and one B(1) atom. In the second H site, H(2) is bonded in an L-shaped geometry to one Mg(1) and one B(1) atom. In the third H site, H(3) is bonded in an L-shaped geometry to one Mg(2) and one B(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg(BH4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.698
_cell_length_b   7.698
_cell_length_c   7.698
_cell_angle_alpha   115.252
_cell_angle_beta   115.252
_cell_angle_gamma   98.442
_symmetry_Int_Tables_number   1
_cell_volume   341.643
_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  0.250  0.750  0.500  1.0
  Mg  Mg1  1  0.000  0.000  0.000  1.0
  B  B2  1  0.619  0.849  0.769  1.0
  B  B3  1  0.080  0.849  0.231  1.0
  B  B4  1  0.151  0.381  0.231  1.0
  B  B5  1  0.151  0.920  0.769  1.0
  H  H6  1  0.480  0.729  0.751  1.0
  H  H7  1  0.977  0.729  0.249  1.0
  H  H8  1  0.271  0.520  0.249  1.0
  H  H9  1  0.271  0.023  0.751  1.0
  H  H10  1  0.272  0.915  0.357  1.0
  H  H11  1  0.558  0.915  0.643  1.0
  H  H12  1  0.085  0.728  0.643  1.0
  H  H13  1  0.085  0.442  0.357  1.0
  H  H14  1  0.718  0.002  0.967  1.0
  H  H15  1  0.035  0.751  0.033  1.0
  H  H16  1  0.035  0.002  0.284  1.0
  H  H17  1  0.718  0.751  0.716  1.0
  H  H18  1  0.249  0.282  0.284  1.0
  H  H19  1  0.998  0.965  0.716  1.0
  H  H20  1  0.249  0.965  0.967  1.0
  H  H21  1  0.998  0.282  0.033  1.0
[/CIF]
.