The structure described by V4O9 crystallizes in the orthorhombic Cmcm space group. There are three inequivalent V sites. In the first V site, V(1) is bonded to one O(2), one O(6), two equivalent O(4), and two equivalent O(7) atoms to form VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with four equivalent V(3)O4 tetrahedra, and  an edgeedge with one V(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-6°. In the second V site, V(2) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(7) atoms to form VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with four equivalent V(3)O4 tetrahedra, and  an edgeedge with one V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-5°. In the third V site, V(3) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form VO4 tetrahedra that share corners with two equivalent V(1)O6 octahedra, corners with two equivalent V(2)O6 octahedra, and  a cornercorner with one V(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-53°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent V(2) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent V(1) atoms. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one V(2) and one V(3) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one V(1) and one V(3) atom. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent V(3) atoms. In the sixth O site, O(6) is bonded in a linear geometry to one V(1) and one V(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one V(1), one V(2), and one V(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_V4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.934
_cell_length_b   6.934
_cell_length_c   7.582
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   102.273
_symmetry_Int_Tables_number   1
_cell_volume   356.223
_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
  O  O0  1  0.325  0.325  0.500  1.0
  O  O1  1  0.675  0.675  0.500  1.0
  O  O2  1  0.297  0.029  0.282  1.0
  O  O3  1  0.971  0.703  0.718  1.0
  O  O4  1  0.297  0.029  0.718  1.0
  O  O5  1  0.971  0.703  0.282  1.0
  O  O6  1  0.703  0.971  0.718  1.0
  O  O7  1  0.029  0.297  0.282  1.0
  O  O8  1  0.703  0.971  0.282  1.0
  O  O9  1  0.029  0.297  0.718  1.0
  O  O10  1  0.206  0.794  0.000  1.0
  O  O11  1  0.794  0.206  0.000  1.0
  O  O12  1  0.311  0.311  0.000  1.0
  O  O13  1  0.689  0.689  0.000  1.0
  O  O14  1  0.376  0.624  0.265  1.0
  O  O15  1  0.376  0.624  0.735  1.0
  O  O16  1  0.624  0.376  0.735  1.0
  O  O17  1  0.624  0.376  0.265  1.0
  V  V18  1  0.685  0.685  0.258  1.0
  V  V19  1  0.315  0.315  0.742  1.0
  V  V20  1  0.685  0.685  0.742  1.0
  V  V21  1  0.315  0.315  0.258  1.0
  V  V22  1  0.213  0.787  0.229  1.0
  V  V23  1  0.213  0.787  0.771  1.0
  V  V24  1  0.787  0.213  0.771  1.0
  V  V25  1  0.787  0.213  0.229  1.0
[/CIF]
.
The structure described by V4O9 crystallizes in the orthorhombic Cmcm space group. There are three inequivalent V sites. In the first V site, V(1) is bonded to one O(2), one O(6), two equivalent O(4), and two equivalent O(7) atoms to form VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with four equivalent V(3)O4 tetrahedra, and  an edgeedge with one V(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-6°. In the second V site, V(2) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(7) atoms to form VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with four equivalent V(3)O4 tetrahedra, and  an edgeedge with one V(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-5°. In the third V site, V(3) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form VO4 tetrahedra that share corners with two equivalent V(1)O6 octahedra, corners with two equivalent V(2)O6 octahedra, and  a cornercorner with one V(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-53°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent V(2) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent V(1) atoms. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one V(2) and one V(3) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one V(1) and one V(3) atom. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent V(3) atoms. In the sixth O site, O(6) is bonded in a linear geometry to one V(1) and one V(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one V(1), one V(2), and one V(3) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_V4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.934
_cell_length_b   6.934
_cell_length_c   7.582
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   102.273
_symmetry_Int_Tables_number   1
_cell_volume   356.223
_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
  O  O0  1  0.325  0.325  0.500  1.0
  O  O1  1  0.675  0.675  0.500  1.0
  O  O2  1  0.297  0.029  0.282  1.0
  O  O3  1  0.971  0.703  0.718  1.0
  O  O4  1  0.297  0.029  0.718  1.0
  O  O5  1  0.971  0.703  0.282  1.0
  O  O6  1  0.703  0.971  0.718  1.0
  O  O7  1  0.029  0.297  0.282  1.0
  O  O8  1  0.703  0.971  0.282  1.0
  O  O9  1  0.029  0.297  0.718  1.0
  O  O10  1  0.206  0.794  0.000  1.0
  O  O11  1  0.794  0.206  0.000  1.0
  O  O12  1  0.311  0.311  0.000  1.0
  O  O13  1  0.689  0.689  0.000  1.0
  O  O14  1  0.376  0.624  0.265  1.0
  O  O15  1  0.376  0.624  0.735  1.0
  O  O16  1  0.624  0.376  0.735  1.0
  O  O17  1  0.624  0.376  0.265  1.0
  V  V18  1  0.685  0.685  0.258  1.0
  V  V19  1  0.315  0.315  0.742  1.0
  V  V20  1  0.685  0.685  0.742  1.0
  V  V21  1  0.315  0.315  0.258  1.0
  V  V22  1  0.213  0.787  0.229  1.0
  V  V23  1  0.213  0.787  0.771  1.0
  V  V24  1  0.787  0.213  0.771  1.0
  V  V25  1  0.787  0.213  0.229  1.0
[/CIF]
.