The crystal structure described by Mg4B8H31 crystallizes in the triclinic P1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one H(10), one H(19), one H(2), one H(23), one H(24), one H(25), one H(29), and one H(4) atom to form distorted MgH8 hexagonal bipyramids that share  an edgeedge with one B(4)H4 tetrahedra,  an edgeedge with one B(5)H4 tetrahedra,  an edgeedge with one B(6)H4 tetrahedra, and  an edgeedge with one B(7)H4 tetrahedra. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one B(2), one H(15), one H(21), one H(30), one H(31), one H(7), one H(8), and one H(9) atom. In the third Mg site, Mg(3) is bonded in a distorted body-centered cubic geometry to one H(1), one H(11), one H(16), one H(17), one H(18), one H(20), one H(22), and one H(3) atom. In the fourth Mg site, Mg(4) is bonded in a body-centered cubic geometry to one H(12), one H(13), one H(14), one H(26), one H(27), one H(28), one H(5), and one H(6) atom. There are eight inequivalent B sites. In the first B site, B(1) is bonded in a tetrahedral geometry to one H(14), one H(27), one H(30), and one H(7) atom. In the second B site, B(2) is bonded in a trigonal planar geometry to one Mg(2), one H(16), one H(20), and one H(9) atom. In the third B site, B(3) is bonded in a tetrahedral geometry to one H(1), one H(17), one H(21), and one H(8) atom. In the fourth B site, B(4) is bonded to one H(11), one H(18), one H(2), and one H(23) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the fifth B site, B(5) is bonded to one H(10), one H(19), one H(22), and one H(3) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the sixth B site, B(6) is bonded to one H(13), one H(24), one H(28), and one H(4) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the seventh B site, B(7) is bonded to one H(12), one H(25), one H(29), and one H(5) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the eighth B site, B(8) is bonded in a tetrahedral geometry to one H(15), one H(26), one H(31), and one H(6) atom. There are thirty-one inequivalent H sites. In the first H site, H(1) is bonded in an L-shaped geometry to one Mg(3) and one B(3) atom. In the second H site, H(2) is bonded in an L-shaped geometry to one Mg(1) and one B(4) atom. In the third H site, H(3) is bonded in an L-shaped geometry to one Mg(3) and one B(5) atom. In the fourth H site, H(4) is bonded in an L-shaped geometry to one Mg(1) and one B(6) atom. In the fifth H site, H(5) is bonded in an L-shaped geometry to one Mg(4) and one B(7) atom. In the sixth H site, H(6) is bonded in an L-shaped geometry to one Mg(4) and one B(8) atom. In the seventh H site, H(7) is bonded in an L-shaped geometry to one Mg(2) and one B(1) atom. In the eighth H site, H(8) is bonded in an L-shaped geometry to one Mg(2) and one B(3) atom. In the ninth H site, H(9) is bonded in a distorted L-shaped geometry to one Mg(2) and one B(2) atom. In the tenth H site, H(10) is bonded in an L-shaped geometry to one Mg(1) and one B(5) atom. In the eleventh H site, H(11) is bonded in an L-shaped geometry to one Mg(3) and one B(4) atom. In the twelfth H site, H(12) is bonded in an L-shaped geometry to one Mg(4) and one B(7) atom. In the thirteenth H site, H(13) is bonded in an L-shaped geometry to one Mg(4) and one B(6) atom. In the fourteenth H site, H(14) is bonded in an L-shaped geometry to one Mg(4) and one B(1) atom. In the fifteenth H site, H(15) is bonded in an L-shaped geometry to one Mg(2) and one B(8) atom. In the sixteenth H site, H(16) is bonded in a distorted L-shaped geometry to one Mg(3) and one B(2) atom. In the seventeenth H site, H(17) is bonded in an L-shaped geometry to one Mg(3) and one B(3) atom. In the eighteenth H site, H(18) is bonded in an L-shaped geometry to one Mg(3) and one B(4) atom. In the nineteenth H site, H(19) is bonded in an L-shaped geometry to one Mg(1) and one B(5) atom. In the twentieth H site, H(20) is bonded in a distorted L-shaped geometry to one Mg(3) and one B(2) atom. In the twenty-first H site, H(21) is bonded in an L-shaped geometry to one Mg(2) and one B(3) atom. In the twenty-second H site, H(22) is bonded in an L-shaped geometry to one Mg(3) and one B(5) atom. In the twenty-third H site, H(23) is bonded in an L-shaped geometry to one Mg(1) and one B(4) atom. In the twenty-fourth H site, H(24) is bonded in an L-shaped geometry to one Mg(1) and one B(6) atom. In the twenty-fifth H site, H(25) is bonded in an L-shaped geometry to one Mg(1) and one B(7) atom. In the twenty-sixth H site, H(26) is bonded in an L-shaped geometry to one Mg(4) and one B(8) atom. In the twenty-seventh H site, H(27) is bonded in an L-shaped geometry to one Mg(4) and one B(1) atom. In the twenty-eighth H site, H(28) is bonded in an L-shaped geometry to one Mg(4) and one B(6) atom. In the twenty-ninth H site, H(29) is bonded in an L-shaped geometry to one Mg(1) and one B(7) atom. In the thirtieth H site, H(30) is bonded in an L-shaped geometry to one Mg(2) and one B(1) atom. In the thirty-first H site, H(31) is bonded in an L-shaped geometry to one Mg(2) and one B(8) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg4B8H31
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.253
_cell_length_b   8.283
_cell_length_c   10.152
_cell_angle_alpha   89.986
_cell_angle_beta   90.394
_cell_angle_gamma   89.998
_symmetry_Int_Tables_number   1
_cell_volume   693.944
_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  0.883  0.510  0.254  1.0
  Mg  Mg1  1  0.386  0.990  0.752  1.0
  Mg  Mg2  1  0.888  0.006  0.007  1.0
  Mg  Mg3  1  0.385  0.494  0.502  1.0
  B  B4  1  0.386  0.718  0.657  1.0
  B  B5  1  0.112  0.994  0.849  1.0
  B  B6  1  0.654  0.995  0.856  1.0
  B  B7  1  0.884  0.782  0.162  1.0
  B  B8  1  0.883  0.245  0.148  1.0
  B  B9  1  0.152  0.504  0.353  1.0
  B  B10  1  0.615  0.505  0.352  1.0
  B  B11  1  0.386  0.255  0.645  1.0
  H  H12  1  0.724  0.122  0.880  1.0
  H  H13  1  0.886  0.761  0.281  1.0
  H  H14  1  0.759  0.172  0.119  1.0
  H  H15  1  0.134  0.511  0.233  1.0
  H  H16  1  0.541  0.628  0.383  1.0
  H  H17  1  0.261  0.327  0.616  1.0
  H  H18  1  0.383  0.842  0.591  1.0
  H  H19  1  0.639  0.987  0.736  1.0
  H  H20  1  0.116  0.989  0.729  1.0
  H  H21  1  0.883  0.259  0.269  1.0
  H  H22  1  0.010  0.854  0.137  1.0
  H  H23  1  0.544  0.378  0.374  1.0
  H  H24  1  0.225  0.627  0.385  1.0
  H  H25  1  0.511  0.646  0.630  1.0
  H  H26  1  0.388  0.242  0.765  1.0
  H  H27  1  0.088  0.870  0.908  1.0
  H  H28  1  0.726  0.872  0.890  1.0
  H  H29  1  0.760  0.857  0.137  1.0
  H  H30  1  0.881  0.372  0.086  1.0
  H  H31  1  0.091  0.124  0.901  1.0
  H  H32  1  0.526  0.997  0.918  1.0
  H  H33  1  0.009  0.175  0.120  1.0
  H  H34  1  0.882  0.659  0.095  1.0
  H  H35  1  0.027  0.500  0.417  1.0
  H  H36  1  0.632  0.512  0.232  1.0
  H  H37  1  0.511  0.325  0.615  1.0
  H  H38  1  0.261  0.644  0.632  1.0
  H  H39  1  0.224  0.377  0.375  1.0
  H  H40  1  0.741  0.504  0.417  1.0
  H  H41  1  0.388  0.738  0.777  1.0
  H  H42  1  0.384  0.127  0.584  1.0
[/CIF]
.
The crystal structure described by Mg4B8H31 crystallizes in the triclinic P1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one H(10), one H(19), one H(2), one H(23), one H(24), one H(25), one H(29), and one H(4) atom to form distorted MgH8 hexagonal bipyramids that share  an edgeedge with one B(4)H4 tetrahedra,  an edgeedge with one B(5)H4 tetrahedra,  an edgeedge with one B(6)H4 tetrahedra, and  an edgeedge with one B(7)H4 tetrahedra. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to one B(2), one H(15), one H(21), one H(30), one H(31), one H(7), one H(8), and one H(9) atom. In the third Mg site, Mg(3) is bonded in a distorted body-centered cubic geometry to one H(1), one H(11), one H(16), one H(17), one H(18), one H(20), one H(22), and one H(3) atom. In the fourth Mg site, Mg(4) is bonded in a body-centered cubic geometry to one H(12), one H(13), one H(14), one H(26), one H(27), one H(28), one H(5), and one H(6) atom. There are eight inequivalent B sites. In the first B site, B(1) is bonded in a tetrahedral geometry to one H(14), one H(27), one H(30), and one H(7) atom. In the second B site, B(2) is bonded in a trigonal planar geometry to one Mg(2), one H(16), one H(20), and one H(9) atom. In the third B site, B(3) is bonded in a tetrahedral geometry to one H(1), one H(17), one H(21), and one H(8) atom. In the fourth B site, B(4) is bonded to one H(11), one H(18), one H(2), and one H(23) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the fifth B site, B(5) is bonded to one H(10), one H(19), one H(22), and one H(3) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the sixth B site, B(6) is bonded to one H(13), one H(24), one H(28), and one H(4) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the seventh B site, B(7) is bonded to one H(12), one H(25), one H(29), and one H(5) atom to form BH4 tetrahedra that share  an edgeedge with one Mg(1)H8 hexagonal bipyramid. In the eighth B site, B(8) is bonded in a tetrahedral geometry to one H(15), one H(26), one H(31), and one H(6) atom. There are thirty-one inequivalent H sites. In the first H site, H(1) is bonded in an L-shaped geometry to one Mg(3) and one B(3) atom. In the second H site, H(2) is bonded in an L-shaped geometry to one Mg(1) and one B(4) atom. In the third H site, H(3) is bonded in an L-shaped geometry to one Mg(3) and one B(5) atom. In the fourth H site, H(4) is bonded in an L-shaped geometry to one Mg(1) and one B(6) atom. In the fifth H site, H(5) is bonded in an L-shaped geometry to one Mg(4) and one B(7) atom. In the sixth H site, H(6) is bonded in an L-shaped geometry to one Mg(4) and one B(8) atom. In the seventh H site, H(7) is bonded in an L-shaped geometry to one Mg(2) and one B(1) atom. In the eighth H site, H(8) is bonded in an L-shaped geometry to one Mg(2) and one B(3) atom. In the ninth H site, H(9) is bonded in a distorted L-shaped geometry to one Mg(2) and one B(2) atom. In the tenth H site, H(10) is bonded in an L-shaped geometry to one Mg(1) and one B(5) atom. In the eleventh H site, H(11) is bonded in an L-shaped geometry to one Mg(3) and one B(4) atom. In the twelfth H site, H(12) is bonded in an L-shaped geometry to one Mg(4) and one B(7) atom. In the thirteenth H site, H(13) is bonded in an L-shaped geometry to one Mg(4) and one B(6) atom. In the fourteenth H site, H(14) is bonded in an L-shaped geometry to one Mg(4) and one B(1) atom. In the fifteenth H site, H(15) is bonded in an L-shaped geometry to one Mg(2) and one B(8) atom. In the sixteenth H site, H(16) is bonded in a distorted L-shaped geometry to one Mg(3) and one B(2) atom. In the seventeenth H site, H(17) is bonded in an L-shaped geometry to one Mg(3) and one B(3) atom. In the eighteenth H site, H(18) is bonded in an L-shaped geometry to one Mg(3) and one B(4) atom. In the nineteenth H site, H(19) is bonded in an L-shaped geometry to one Mg(1) and one B(5) atom. In the twentieth H site, H(20) is bonded in a distorted L-shaped geometry to one Mg(3) and one B(2) atom. In the twenty-first H site, H(21) is bonded in an L-shaped geometry to one Mg(2) and one B(3) atom. In the twenty-second H site, H(22) is bonded in an L-shaped geometry to one Mg(3) and one B(5) atom. In the twenty-third H site, H(23) is bonded in an L-shaped geometry to one Mg(1) and one B(4) atom. In the twenty-fourth H site, H(24) is bonded in an L-shaped geometry to one Mg(1) and one B(6) atom. In the twenty-fifth H site, H(25) is bonded in an L-shaped geometry to one Mg(1) and one B(7) atom. In the twenty-sixth H site, H(26) is bonded in an L-shaped geometry to one Mg(4) and one B(8) atom. In the twenty-seventh H site, H(27) is bonded in an L-shaped geometry to one Mg(4) and one B(1) atom. In the twenty-eighth H site, H(28) is bonded in an L-shaped geometry to one Mg(4) and one B(6) atom. In the twenty-ninth H site, H(29) is bonded in an L-shaped geometry to one Mg(1) and one B(7) atom. In the thirtieth H site, H(30) is bonded in an L-shaped geometry to one Mg(2) and one B(1) atom. In the thirty-first H site, H(31) is bonded in an L-shaped geometry to one Mg(2) and one B(8) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg4B8H31
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.253
_cell_length_b   8.283
_cell_length_c   10.152
_cell_angle_alpha   89.986
_cell_angle_beta   90.394
_cell_angle_gamma   89.998
_symmetry_Int_Tables_number   1
_cell_volume   693.944
_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  0.883  0.510  0.254  1.0
  Mg  Mg1  1  0.386  0.990  0.752  1.0
  Mg  Mg2  1  0.888  0.006  0.007  1.0
  Mg  Mg3  1  0.385  0.494  0.502  1.0
  B  B4  1  0.386  0.718  0.657  1.0
  B  B5  1  0.112  0.994  0.849  1.0
  B  B6  1  0.654  0.995  0.856  1.0
  B  B7  1  0.884  0.782  0.162  1.0
  B  B8  1  0.883  0.245  0.148  1.0
  B  B9  1  0.152  0.504  0.353  1.0
  B  B10  1  0.615  0.505  0.352  1.0
  B  B11  1  0.386  0.255  0.645  1.0
  H  H12  1  0.724  0.122  0.880  1.0
  H  H13  1  0.886  0.761  0.281  1.0
  H  H14  1  0.759  0.172  0.119  1.0
  H  H15  1  0.134  0.511  0.233  1.0
  H  H16  1  0.541  0.628  0.383  1.0
  H  H17  1  0.261  0.327  0.616  1.0
  H  H18  1  0.383  0.842  0.591  1.0
  H  H19  1  0.639  0.987  0.736  1.0
  H  H20  1  0.116  0.989  0.729  1.0
  H  H21  1  0.883  0.259  0.269  1.0
  H  H22  1  0.010  0.854  0.137  1.0
  H  H23  1  0.544  0.378  0.374  1.0
  H  H24  1  0.225  0.627  0.385  1.0
  H  H25  1  0.511  0.646  0.630  1.0
  H  H26  1  0.388  0.242  0.765  1.0
  H  H27  1  0.088  0.870  0.908  1.0
  H  H28  1  0.726  0.872  0.890  1.0
  H  H29  1  0.760  0.857  0.137  1.0
  H  H30  1  0.881  0.372  0.086  1.0
  H  H31  1  0.091  0.124  0.901  1.0
  H  H32  1  0.526  0.997  0.918  1.0
  H  H33  1  0.009  0.175  0.120  1.0
  H  H34  1  0.882  0.659  0.095  1.0
  H  H35  1  0.027  0.500  0.417  1.0
  H  H36  1  0.632  0.512  0.232  1.0
  H  H37  1  0.511  0.325  0.615  1.0
  H  H38  1  0.261  0.644  0.632  1.0
  H  H39  1  0.224  0.377  0.375  1.0
  H  H40  1  0.741  0.504  0.417  1.0
  H  H41  1  0.388  0.738  0.777  1.0
  H  H42  1  0.384  0.127  0.584  1.0
[/CIF]
.