The crystal structure described by RbTi2(PO4)3 crystallizes in the trigonal R-3 space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to six equivalent O(1) and six equivalent O(4) atoms to form distorted RbO12 cuboctahedra that share corners with six equivalent Ti(2)O6 octahedra, edges with six equivalent P(1)O4 tetrahedra, and faces with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. In the second Rb site, Rb(2) is bonded to six equivalent O(2) and six equivalent O(3) atoms to form distorted RbO12 cuboctahedra that share corners with six equivalent Ti(1)O6 octahedra, edges with six equivalent P(1)O4 tetrahedra, and faces with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TiO6 octahedra that share corners with three equivalent Rb(2)O12 cuboctahedra, corners with six equivalent P(1)O4 tetrahedra, and  a faceface with one Rb(1)O12 cuboctahedra. In the second Ti site, Ti(2) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form TiO6 octahedra that share corners with three equivalent Rb(1)O12 cuboctahedra, corners with six equivalent P(1)O4 tetrahedra, and  a faceface with one Rb(2)O12 cuboctahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra,  an edgeedge with one Rb(1)O12 cuboctahedra, and  an edgeedge with one Rb(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 21-38°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Rb(1), one Ti(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Rb(2), one Ti(1), and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Rb(2), one Ti(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Rb(1), one Ti(2), and one P(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_RbTi2(PO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.301
_cell_length_b   9.301
_cell_length_c   9.301
_cell_angle_alpha   53.825
_cell_angle_beta   53.825
_cell_angle_gamma   53.825
_symmetry_Int_Tables_number   1
_cell_volume   486.822
_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
  Rb  Rb0  1  0.500  0.500  0.500  1.0
  Rb  Rb1  1  0.000  0.000  0.000  1.0
  Ti  Ti2  1  0.349  0.349  0.349  1.0
  Ti  Ti3  1  0.850  0.850  0.850  1.0
  Ti  Ti4  1  0.651  0.651  0.651  1.0
  Ti  Ti5  1  0.150  0.150  0.150  1.0
  P  P6  1  0.970  0.251  0.530  1.0
  P  P7  1  0.530  0.970  0.251  1.0
  P  P8  1  0.251  0.530  0.970  1.0
  P  P9  1  0.749  0.470  0.030  1.0
  P  P10  1  0.030  0.749  0.470  1.0
  P  P11  1  0.470  0.030  0.749  1.0
  O  O12  1  0.559  0.442  0.191  1.0
  O  O13  1  0.486  0.844  0.770  1.0
  O  O14  1  0.294  0.084  0.922  1.0
  O  O15  1  0.442  0.191  0.559  1.0
  O  O16  1  0.353  0.989  0.253  1.0
  O  O17  1  0.706  0.916  0.078  1.0
  O  O18  1  0.916  0.078  0.706  1.0
  O  O19  1  0.770  0.486  0.844  1.0
  O  O20  1  0.809  0.441  0.558  1.0
  O  O21  1  0.156  0.230  0.514  1.0
  O  O22  1  0.989  0.253  0.353  1.0
  O  O23  1  0.191  0.559  0.442  1.0
  O  O24  1  0.558  0.809  0.441  1.0
  O  O25  1  0.011  0.747  0.647  1.0
  O  O26  1  0.230  0.514  0.156  1.0
  O  O27  1  0.078  0.706  0.916  1.0
  O  O28  1  0.084  0.922  0.294  1.0
  O  O29  1  0.844  0.770  0.486  1.0
  O  O30  1  0.922  0.294  0.084  1.0
  O  O31  1  0.647  0.011  0.747  1.0
  O  O32  1  0.253  0.353  0.989  1.0
  O  O33  1  0.514  0.156  0.230  1.0
  O  O34  1  0.441  0.558  0.809  1.0
  O  O35  1  0.747  0.647  0.011  1.0
[/CIF]
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The crystal structure described by RbTi2(PO4)3 crystallizes in the trigonal R-3 space group. There are two inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to six equivalent O(1) and six equivalent O(4) atoms to form distorted RbO12 cuboctahedra that share corners with six equivalent Ti(2)O6 octahedra, edges with six equivalent P(1)O4 tetrahedra, and faces with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. In the second Rb site, Rb(2) is bonded to six equivalent O(2) and six equivalent O(3) atoms to form distorted RbO12 cuboctahedra that share corners with six equivalent Ti(1)O6 octahedra, edges with six equivalent P(1)O4 tetrahedra, and faces with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TiO6 octahedra that share corners with three equivalent Rb(2)O12 cuboctahedra, corners with six equivalent P(1)O4 tetrahedra, and  a faceface with one Rb(1)O12 cuboctahedra. In the second Ti site, Ti(2) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form TiO6 octahedra that share corners with three equivalent Rb(1)O12 cuboctahedra, corners with six equivalent P(1)O4 tetrahedra, and  a faceface with one Rb(2)O12 cuboctahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Ti(1)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra,  an edgeedge with one Rb(1)O12 cuboctahedra, and  an edgeedge with one Rb(2)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 21-38°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Rb(1), one Ti(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Rb(2), one Ti(1), and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Rb(2), one Ti(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Rb(1), one Ti(2), and one P(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_RbTi2(PO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.301
_cell_length_b   9.301
_cell_length_c   9.301
_cell_angle_alpha   53.825
_cell_angle_beta   53.825
_cell_angle_gamma   53.825
_symmetry_Int_Tables_number   1
_cell_volume   486.822
_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
  Rb  Rb0  1  0.500  0.500  0.500  1.0
  Rb  Rb1  1  0.000  0.000  0.000  1.0
  Ti  Ti2  1  0.349  0.349  0.349  1.0
  Ti  Ti3  1  0.850  0.850  0.850  1.0
  Ti  Ti4  1  0.651  0.651  0.651  1.0
  Ti  Ti5  1  0.150  0.150  0.150  1.0
  P  P6  1  0.970  0.251  0.530  1.0
  P  P7  1  0.530  0.970  0.251  1.0
  P  P8  1  0.251  0.530  0.970  1.0
  P  P9  1  0.749  0.470  0.030  1.0
  P  P10  1  0.030  0.749  0.470  1.0
  P  P11  1  0.470  0.030  0.749  1.0
  O  O12  1  0.559  0.442  0.191  1.0
  O  O13  1  0.486  0.844  0.770  1.0
  O  O14  1  0.294  0.084  0.922  1.0
  O  O15  1  0.442  0.191  0.559  1.0
  O  O16  1  0.353  0.989  0.253  1.0
  O  O17  1  0.706  0.916  0.078  1.0
  O  O18  1  0.916  0.078  0.706  1.0
  O  O19  1  0.770  0.486  0.844  1.0
  O  O20  1  0.809  0.441  0.558  1.0
  O  O21  1  0.156  0.230  0.514  1.0
  O  O22  1  0.989  0.253  0.353  1.0
  O  O23  1  0.191  0.559  0.442  1.0
  O  O24  1  0.558  0.809  0.441  1.0
  O  O25  1  0.011  0.747  0.647  1.0
  O  O26  1  0.230  0.514  0.156  1.0
  O  O27  1  0.078  0.706  0.916  1.0
  O  O28  1  0.084  0.922  0.294  1.0
  O  O29  1  0.844  0.770  0.486  1.0
  O  O30  1  0.922  0.294  0.084  1.0
  O  O31  1  0.647  0.011  0.747  1.0
  O  O32  1  0.253  0.353  0.989  1.0
  O  O33  1  0.514  0.156  0.230  1.0
  O  O34  1  0.441  0.558  0.809  1.0
  O  O35  1  0.747  0.647  0.011  1.0
[/CIF]
.