The compound described by CeMg2H7 crystallizes in the tetragonal P4_12_12 space group. Mg(1) is bonded to one H(1), two equivalent H(2), two equivalent H(3), and two equivalent H(4) atoms to form distorted MgH7 pentagonal bipyramids that share corners with two equivalent Ce(1)H12 cuboctahedra, corners with two equivalent Mg(1)H7 pentagonal bipyramids, edges with four equivalent Ce(1)H12 cuboctahedra, and edges with four equivalent Mg(1)H7 pentagonal bipyramids. Ce(1) is bonded to four equivalent H(1), four equivalent H(2), and four equivalent H(3) atoms to form distorted CeH12 cuboctahedra that share corners with four equivalent Mg(1)H7 pentagonal bipyramids, edges with eight equivalent Mg(1)H7 pentagonal bipyramids, and faces with four equivalent Ce(1)H12 cuboctahedra. There are four inequivalent H sites. In the first H site, H(4) is bonded to four equivalent Mg(1) atoms to form HMg4 tetrahedra that share corners with four equivalent H(2)Ce2Mg2 tetrahedra, corners with four equivalent H(3)Ce2Mg2 tetrahedra, corners with four equivalent H(4)Mg4 tetrahedra, edges with two equivalent H(2)Ce2Mg2 tetrahedra, and edges with two equivalent H(3)Ce2Mg2 tetrahedra. In the second H site, H(1) is bonded in a 3-coordinate geometry to one Mg(1) and two equivalent Ce(1) atoms. In the third H site, H(2) is bonded to two equivalent Mg(1) and two equivalent Ce(1) atoms to form HCe2Mg2 tetrahedra that share corners with two equivalent H(4)Mg4 tetrahedra, corners with four equivalent H(2)Ce2Mg2 tetrahedra, corners with six equivalent H(3)Ce2Mg2 tetrahedra,  an edgeedge with one H(4)Mg4 tetrahedra, edges with two equivalent H(2)Ce2Mg2 tetrahedra, and edges with three equivalent H(3)Ce2Mg2 tetrahedra. In the fourth H site, H(3) is bonded to two equivalent Mg(1) and two equivalent Ce(1) atoms to form distorted HCe2Mg2 tetrahedra that share corners with two equivalent H(4)Mg4 tetrahedra, corners with six equivalent H(2)Ce2Mg2 tetrahedra, corners with eight equivalent H(3)Ce2Mg2 tetrahedra,  an edgeedge with one H(4)Mg4 tetrahedra, and edges with three equivalent H(2)Ce2Mg2 tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_CeMg2H7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.281
_cell_length_b   6.281
_cell_length_c   9.436
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   372.211
_cell_formula_units_Z   4
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
  Ce  Ce0  1  0.771  0.229  0.750  1.0
  Ce  Ce1  1  0.229  0.771  0.250  1.0
  Ce  Ce2  1  0.729  0.729  0.500  1.0
  Ce  Ce3  1  0.271  0.271  0.000  1.0
  Mg  Mg4  1  0.527  0.237  0.400  1.0
  Mg  Mg5  1  0.473  0.763  0.900  1.0
  Mg  Mg6  1  0.737  0.973  0.150  1.0
  Mg  Mg7  1  0.263  0.027  0.650  1.0
  Mg  Mg8  1  0.763  0.473  0.100  1.0
  Mg  Mg9  1  0.237  0.527  0.600  1.0
  Mg  Mg10  1  0.973  0.737  0.850  1.0
  Mg  Mg11  1  0.027  0.263  0.350  1.0
  H  H12  1  0.535  0.471  0.621  1.0
  H  H13  1  0.465  0.529  0.121  1.0
  H  H14  1  0.971  0.965  0.371  1.0
  H  H15  1  0.029  0.035  0.871  1.0
  H  H16  1  0.529  0.465  0.879  1.0
  H  H17  1  0.471  0.535  0.379  1.0
  H  H18  1  0.965  0.971  0.629  1.0
  H  H19  1  0.035  0.029  0.129  1.0
  H  H20  1  0.572  0.064  0.573  1.0
  H  H21  1  0.428  0.936  0.073  1.0
  H  H22  1  0.564  0.928  0.323  1.0
  H  H23  1  0.436  0.072  0.823  1.0
  H  H24  1  0.936  0.428  0.927  1.0
  H  H25  1  0.064  0.572  0.427  1.0
  H  H26  1  0.928  0.564  0.677  1.0
  H  H27  1  0.072  0.436  0.177  1.0
  H  H28  1  0.804  0.340  0.495  1.0
  H  H29  1  0.196  0.660  0.995  1.0
  H  H30  1  0.840  0.696  0.245  1.0
  H  H31  1  0.160  0.304  0.745  1.0
  H  H32  1  0.660  0.196  0.005  1.0
  H  H33  1  0.340  0.804  0.505  1.0
  H  H34  1  0.696  0.840  0.755  1.0
  H  H35  1  0.304  0.160  0.255  1.0
  H  H36  1  0.256  0.744  0.750  1.0
  H  H37  1  0.744  0.256  0.250  1.0
  H  H38  1  0.244  0.244  0.500  1.0
  H  H39  1  0.756  0.756  0.000  1.0
[/CIF]
.
The compound described by CeMg2H7 crystallizes in the tetragonal P4_12_12 space group. Mg(1) is bonded to one H(1), two equivalent H(2), two equivalent H(3), and two equivalent H(4) atoms to form distorted MgH7 pentagonal bipyramids that share corners with two equivalent Ce(1)H12 cuboctahedra, corners with two equivalent Mg(1)H7 pentagonal bipyramids, edges with four equivalent Ce(1)H12 cuboctahedra, and edges with four equivalent Mg(1)H7 pentagonal bipyramids. Ce(1) is bonded to four equivalent H(1), four equivalent H(2), and four equivalent H(3) atoms to form distorted CeH12 cuboctahedra that share corners with four equivalent Mg(1)H7 pentagonal bipyramids, edges with eight equivalent Mg(1)H7 pentagonal bipyramids, and faces with four equivalent Ce(1)H12 cuboctahedra. There are four inequivalent H sites. In the first H site, H(4) is bonded to four equivalent Mg(1) atoms to form HMg4 tetrahedra that share corners with four equivalent H(2)Ce2Mg2 tetrahedra, corners with four equivalent H(3)Ce2Mg2 tetrahedra, corners with four equivalent H(4)Mg4 tetrahedra, edges with two equivalent H(2)Ce2Mg2 tetrahedra, and edges with two equivalent H(3)Ce2Mg2 tetrahedra. In the second H site, H(1) is bonded in a 3-coordinate geometry to one Mg(1) and two equivalent Ce(1) atoms. In the third H site, H(2) is bonded to two equivalent Mg(1) and two equivalent Ce(1) atoms to form HCe2Mg2 tetrahedra that share corners with two equivalent H(4)Mg4 tetrahedra, corners with four equivalent H(2)Ce2Mg2 tetrahedra, corners with six equivalent H(3)Ce2Mg2 tetrahedra,  an edgeedge with one H(4)Mg4 tetrahedra, edges with two equivalent H(2)Ce2Mg2 tetrahedra, and edges with three equivalent H(3)Ce2Mg2 tetrahedra. In the fourth H site, H(3) is bonded to two equivalent Mg(1) and two equivalent Ce(1) atoms to form distorted HCe2Mg2 tetrahedra that share corners with two equivalent H(4)Mg4 tetrahedra, corners with six equivalent H(2)Ce2Mg2 tetrahedra, corners with eight equivalent H(3)Ce2Mg2 tetrahedra,  an edgeedge with one H(4)Mg4 tetrahedra, and edges with three equivalent H(2)Ce2Mg2 tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_CeMg2H7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.281
_cell_length_b   6.281
_cell_length_c   9.436
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   372.211
_cell_formula_units_Z   4
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
  Ce  Ce0  1  0.771  0.229  0.750  1.0
  Ce  Ce1  1  0.229  0.771  0.250  1.0
  Ce  Ce2  1  0.729  0.729  0.500  1.0
  Ce  Ce3  1  0.271  0.271  0.000  1.0
  Mg  Mg4  1  0.527  0.237  0.400  1.0
  Mg  Mg5  1  0.473  0.763  0.900  1.0
  Mg  Mg6  1  0.737  0.973  0.150  1.0
  Mg  Mg7  1  0.263  0.027  0.650  1.0
  Mg  Mg8  1  0.763  0.473  0.100  1.0
  Mg  Mg9  1  0.237  0.527  0.600  1.0
  Mg  Mg10  1  0.973  0.737  0.850  1.0
  Mg  Mg11  1  0.027  0.263  0.350  1.0
  H  H12  1  0.535  0.471  0.621  1.0
  H  H13  1  0.465  0.529  0.121  1.0
  H  H14  1  0.971  0.965  0.371  1.0
  H  H15  1  0.029  0.035  0.871  1.0
  H  H16  1  0.529  0.465  0.879  1.0
  H  H17  1  0.471  0.535  0.379  1.0
  H  H18  1  0.965  0.971  0.629  1.0
  H  H19  1  0.035  0.029  0.129  1.0
  H  H20  1  0.572  0.064  0.573  1.0
  H  H21  1  0.428  0.936  0.073  1.0
  H  H22  1  0.564  0.928  0.323  1.0
  H  H23  1  0.436  0.072  0.823  1.0
  H  H24  1  0.936  0.428  0.927  1.0
  H  H25  1  0.064  0.572  0.427  1.0
  H  H26  1  0.928  0.564  0.677  1.0
  H  H27  1  0.072  0.436  0.177  1.0
  H  H28  1  0.804  0.340  0.495  1.0
  H  H29  1  0.196  0.660  0.995  1.0
  H  H30  1  0.840  0.696  0.245  1.0
  H  H31  1  0.160  0.304  0.745  1.0
  H  H32  1  0.660  0.196  0.005  1.0
  H  H33  1  0.340  0.804  0.505  1.0
  H  H34  1  0.696  0.840  0.755  1.0
  H  H35  1  0.304  0.160  0.255  1.0
  H  H36  1  0.256  0.744  0.750  1.0
  H  H37  1  0.744  0.256  0.250  1.0
  H  H38  1  0.244  0.244  0.500  1.0
  H  H39  1  0.756  0.756  0.000  1.0
[/CIF]
.