The material structure described by MoSi2O7 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mo(2)O6 octahedra. In the second Mo site, Mo(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mo(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Mo(1)O6 octahedra,  a cornercorner with one Mo(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-50°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mo(1)O6 octahedra,  a cornercorner with one Mo(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-49°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(7) is bonded in a single-bond geometry to one Si(1) atom. In the third O site, O(1) is bonded in a bent 120 degrees geometry to one Mo(2) and one Si(2) atom. In the fourth O site, O(2) is bonded in a water-like geometry to one Mo(1) and one Mo(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mo(1) and one Si(2) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Mo(1), one Mo(2), and one Si(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Si2MoO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.190
_cell_length_b   9.190
_cell_length_c   10.109
_cell_angle_alpha   63.910
_cell_angle_beta   63.910
_cell_angle_gamma   51.591
_symmetry_Int_Tables_number   1
_cell_volume   583.814
_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
  Si  Si0  1  0.524  0.134  0.653  1.0
  Si  Si1  1  0.134  0.524  0.153  1.0
  Si  Si2  1  0.539  0.186  0.107  1.0
  Si  Si3  1  0.186  0.539  0.607  1.0
  Si  Si4  1  0.866  0.476  0.847  1.0
  Si  Si5  1  0.461  0.814  0.893  1.0
  Si  Si6  1  0.814  0.461  0.393  1.0
  Si  Si7  1  0.476  0.866  0.347  1.0
  Mo  Mo8  1  0.781  0.219  0.750  1.0
  Mo  Mo9  1  0.219  0.781  0.250  1.0
  Mo  Mo10  1  0.000  0.000  0.000  1.0
  Mo  Mo11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.887  0.256  0.371  1.0
  O  O13  1  0.959  0.916  0.390  1.0
  O  O14  1  0.432  0.746  0.083  1.0
  O  O15  1  0.916  0.959  0.890  1.0
  O  O16  1  0.265  0.903  0.352  1.0
  O  O17  1  0.008  0.509  0.683  1.0
  O  O18  1  0.746  0.432  0.583  1.0
  O  O19  1  0.097  0.735  0.148  1.0
  O  O20  1  0.992  0.491  0.317  1.0
  O  O21  1  0.626  0.643  0.329  1.0
  O  O22  1  0.041  0.084  0.610  1.0
  O  O23  1  0.735  0.097  0.648  1.0
  O  O24  1  0.491  0.992  0.817  1.0
  O  O25  1  0.256  0.887  0.871  1.0
  O  O26  1  0.643  0.626  0.829  1.0
  O  O27  1  0.903  0.265  0.852  1.0
  O  O28  1  0.892  0.464  0.999  1.0
  O  O29  1  0.374  0.357  0.671  1.0
  O  O30  1  0.536  0.108  0.501  1.0
  O  O31  1  0.357  0.374  0.171  1.0
  O  O32  1  0.509  0.008  0.183  1.0
  O  O33  1  0.084  0.041  0.110  1.0
  O  O34  1  0.464  0.892  0.499  1.0
  O  O35  1  0.568  0.254  0.917  1.0
  O  O36  1  0.108  0.536  0.001  1.0
  O  O37  1  0.254  0.568  0.417  1.0
  O  O38  1  0.744  0.113  0.129  1.0
  O  O39  1  0.113  0.744  0.629  1.0
[/CIF]
.
The material structure described by MoSi2O7 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted MoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mo(2)O6 octahedra. In the second Mo site, Mo(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MoO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Mo(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Mo(1)O6 octahedra,  a cornercorner with one Mo(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-50°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Mo(1)O6 octahedra,  a cornercorner with one Mo(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-49°. There are seven inequivalent O sites. In the first O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(7) is bonded in a single-bond geometry to one Si(1) atom. In the third O site, O(1) is bonded in a bent 120 degrees geometry to one Mo(2) and one Si(2) atom. In the fourth O site, O(2) is bonded in a water-like geometry to one Mo(1) and one Mo(2) atom. In the fifth O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mo(1) and one Si(2) atom. In the sixth O site, O(4) is bonded in a 3-coordinate geometry to one Mo(1), one Mo(2), and one Si(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Si2MoO7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.190
_cell_length_b   9.190
_cell_length_c   10.109
_cell_angle_alpha   63.910
_cell_angle_beta   63.910
_cell_angle_gamma   51.591
_symmetry_Int_Tables_number   1
_cell_volume   583.814
_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
  Si  Si0  1  0.524  0.134  0.653  1.0
  Si  Si1  1  0.134  0.524  0.153  1.0
  Si  Si2  1  0.539  0.186  0.107  1.0
  Si  Si3  1  0.186  0.539  0.607  1.0
  Si  Si4  1  0.866  0.476  0.847  1.0
  Si  Si5  1  0.461  0.814  0.893  1.0
  Si  Si6  1  0.814  0.461  0.393  1.0
  Si  Si7  1  0.476  0.866  0.347  1.0
  Mo  Mo8  1  0.781  0.219  0.750  1.0
  Mo  Mo9  1  0.219  0.781  0.250  1.0
  Mo  Mo10  1  0.000  0.000  0.000  1.0
  Mo  Mo11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.887  0.256  0.371  1.0
  O  O13  1  0.959  0.916  0.390  1.0
  O  O14  1  0.432  0.746  0.083  1.0
  O  O15  1  0.916  0.959  0.890  1.0
  O  O16  1  0.265  0.903  0.352  1.0
  O  O17  1  0.008  0.509  0.683  1.0
  O  O18  1  0.746  0.432  0.583  1.0
  O  O19  1  0.097  0.735  0.148  1.0
  O  O20  1  0.992  0.491  0.317  1.0
  O  O21  1  0.626  0.643  0.329  1.0
  O  O22  1  0.041  0.084  0.610  1.0
  O  O23  1  0.735  0.097  0.648  1.0
  O  O24  1  0.491  0.992  0.817  1.0
  O  O25  1  0.256  0.887  0.871  1.0
  O  O26  1  0.643  0.626  0.829  1.0
  O  O27  1  0.903  0.265  0.852  1.0
  O  O28  1  0.892  0.464  0.999  1.0
  O  O29  1  0.374  0.357  0.671  1.0
  O  O30  1  0.536  0.108  0.501  1.0
  O  O31  1  0.357  0.374  0.171  1.0
  O  O32  1  0.509  0.008  0.183  1.0
  O  O33  1  0.084  0.041  0.110  1.0
  O  O34  1  0.464  0.892  0.499  1.0
  O  O35  1  0.568  0.254  0.917  1.0
  O  O36  1  0.108  0.536  0.001  1.0
  O  O37  1  0.254  0.568  0.417  1.0
  O  O38  1  0.744  0.113  0.129  1.0
  O  O39  1  0.113  0.744  0.629  1.0
[/CIF]
.