The compound described by Na4TaAl(SiO4)3 crystallizes in the trigonal R3c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to three equivalent O(3) and three equivalent O(4) atoms. Ta(1) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form TaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Al(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Ta(1)O6 octahedra and corners with two equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-36°. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Na(2), two equivalent Na(1), one Al(1), and one Si(1) atom to form distorted ONa3AlSi trigonal bipyramids that share corners with six equivalent O(4)Na3TaSi trigonal bipyramids,  an edgeedge with one O(4)Na3TaSi trigonal bipyramid, and faces with two equivalent O(3)Na3AlSi trigonal bipyramids. In the second O site, O(4) is bonded to one Na(2), two equivalent Na(1), one Ta(1), and one Si(1) atom to form distorted ONa3TaSi trigonal bipyramids that share corners with six equivalent O(3)Na3AlSi trigonal bipyramids,  an edgeedge with one O(3)Na3AlSi trigonal bipyramid, and faces with two equivalent O(4)Na3TaSi trigonal bipyramids. In the third O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Na(1), one Al(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Na(1), one Ta(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na4TaAl(SiO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.978
_cell_length_b   8.978
_cell_length_c   8.991
_cell_angle_alpha   60.047
_cell_angle_beta   60.047
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   512.819
_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
  Al  Al0  1  0.353  0.353  0.942  1.0
  Al  Al1  1  0.853  0.853  0.442  1.0
  Na  Na2  1  0.239  0.620  0.257  1.0
  Na  Na3  1  0.884  0.239  0.257  1.0
  Na  Na4  1  0.620  0.884  0.257  1.0
  Na  Na5  1  0.120  0.739  0.757  1.0
  Na  Na6  1  0.384  0.120  0.757  1.0
  Na  Na7  1  0.739  0.384  0.757  1.0
  Na  Na8  1  0.495  0.495  0.515  1.0
  Na  Na9  1  0.995  0.995  0.015  1.0
  O  O10  1  0.277  0.145  0.068  1.0
  O  O11  1  0.509  0.277  0.068  1.0
  O  O12  1  0.145  0.509  0.068  1.0
  O  O13  1  0.645  0.777  0.568  1.0
  O  O14  1  0.009  0.645  0.568  1.0
  O  O15  1  0.777  0.009  0.568  1.0
  O  O16  1  0.726  0.858  0.925  1.0
  O  O17  1  0.491  0.726  0.925  1.0
  O  O18  1  0.858  0.491  0.925  1.0
  O  O19  1  0.358  0.226  0.425  1.0
  O  O20  1  0.991  0.358  0.425  1.0
  O  O21  1  0.226  0.991  0.425  1.0
  O  O22  1  0.571  0.227  0.768  1.0
  O  O23  1  0.434  0.571  0.768  1.0
  O  O24  1  0.227  0.434  0.768  1.0
  O  O25  1  0.727  0.071  0.268  1.0
  O  O26  1  0.934  0.727  0.268  1.0
  O  O27  1  0.071  0.934  0.268  1.0
  O  O28  1  0.427  0.777  0.233  1.0
  O  O29  1  0.563  0.427  0.233  1.0
  O  O30  1  0.777  0.563  0.233  1.0
  O  O31  1  0.277  0.927  0.733  1.0
  O  O32  1  0.063  0.277  0.733  1.0
  O  O33  1  0.927  0.063  0.733  1.0
  Si  Si34  1  0.246  0.967  0.242  1.0
  Si  Si35  1  0.545  0.246  0.242  1.0
  Si  Si36  1  0.967  0.545  0.242  1.0
  Si  Si37  1  0.467  0.746  0.742  1.0
  Si  Si38  1  0.045  0.467  0.742  1.0
  Si  Si39  1  0.746  0.045  0.742  1.0
  Ta  Ta40  1  0.646  0.646  0.061  1.0
  Ta  Ta41  1  0.146  0.146  0.561  1.0
[/CIF]
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The compound described by Na4TaAl(SiO4)3 crystallizes in the trigonal R3c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to three equivalent O(3) and three equivalent O(4) atoms. Ta(1) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form TaO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Al(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form AlO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Ta(1)O6 octahedra and corners with two equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-36°. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Na(2), two equivalent Na(1), one Al(1), and one Si(1) atom to form distorted ONa3AlSi trigonal bipyramids that share corners with six equivalent O(4)Na3TaSi trigonal bipyramids,  an edgeedge with one O(4)Na3TaSi trigonal bipyramid, and faces with two equivalent O(3)Na3AlSi trigonal bipyramids. In the second O site, O(4) is bonded to one Na(2), two equivalent Na(1), one Ta(1), and one Si(1) atom to form distorted ONa3TaSi trigonal bipyramids that share corners with six equivalent O(3)Na3AlSi trigonal bipyramids,  an edgeedge with one O(3)Na3AlSi trigonal bipyramid, and faces with two equivalent O(4)Na3TaSi trigonal bipyramids. In the third O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Na(1), one Al(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to two equivalent Na(1), one Ta(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na4TaAl(SiO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.978
_cell_length_b   8.978
_cell_length_c   8.991
_cell_angle_alpha   60.047
_cell_angle_beta   60.047
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   512.819
_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
  Al  Al0  1  0.353  0.353  0.942  1.0
  Al  Al1  1  0.853  0.853  0.442  1.0
  Na  Na2  1  0.239  0.620  0.257  1.0
  Na  Na3  1  0.884  0.239  0.257  1.0
  Na  Na4  1  0.620  0.884  0.257  1.0
  Na  Na5  1  0.120  0.739  0.757  1.0
  Na  Na6  1  0.384  0.120  0.757  1.0
  Na  Na7  1  0.739  0.384  0.757  1.0
  Na  Na8  1  0.495  0.495  0.515  1.0
  Na  Na9  1  0.995  0.995  0.015  1.0
  O  O10  1  0.277  0.145  0.068  1.0
  O  O11  1  0.509  0.277  0.068  1.0
  O  O12  1  0.145  0.509  0.068  1.0
  O  O13  1  0.645  0.777  0.568  1.0
  O  O14  1  0.009  0.645  0.568  1.0
  O  O15  1  0.777  0.009  0.568  1.0
  O  O16  1  0.726  0.858  0.925  1.0
  O  O17  1  0.491  0.726  0.925  1.0
  O  O18  1  0.858  0.491  0.925  1.0
  O  O19  1  0.358  0.226  0.425  1.0
  O  O20  1  0.991  0.358  0.425  1.0
  O  O21  1  0.226  0.991  0.425  1.0
  O  O22  1  0.571  0.227  0.768  1.0
  O  O23  1  0.434  0.571  0.768  1.0
  O  O24  1  0.227  0.434  0.768  1.0
  O  O25  1  0.727  0.071  0.268  1.0
  O  O26  1  0.934  0.727  0.268  1.0
  O  O27  1  0.071  0.934  0.268  1.0
  O  O28  1  0.427  0.777  0.233  1.0
  O  O29  1  0.563  0.427  0.233  1.0
  O  O30  1  0.777  0.563  0.233  1.0
  O  O31  1  0.277  0.927  0.733  1.0
  O  O32  1  0.063  0.277  0.733  1.0
  O  O33  1  0.927  0.063  0.733  1.0
  Si  Si34  1  0.246  0.967  0.242  1.0
  Si  Si35  1  0.545  0.246  0.242  1.0
  Si  Si36  1  0.967  0.545  0.242  1.0
  Si  Si37  1  0.467  0.746  0.742  1.0
  Si  Si38  1  0.045  0.467  0.742  1.0
  Si  Si39  1  0.746  0.045  0.742  1.0
  Ta  Ta40  1  0.646  0.646  0.061  1.0
  Ta  Ta41  1  0.146  0.146  0.561  1.0
[/CIF]
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