The material described by Li2CaTa2O7 crystallizes in the orthorhombic Pnma space group. Li(1) is bonded to one O(3) and four equivalent O(2) atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Li(1)O5 trigonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with four equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 59°. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(4) atoms. Ta(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and edges with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 22-31°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Li(1), one Ca(1), and two equivalent Ta(1) atoms. In the second O site, O(4) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 trigonal pyramids that share corners with four equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids,  an edgeedge with one O(1)Ca2Ta2 tetrahedra, and edges with three equivalent O(4)Ca2Ta2 trigonal pyramids. In the third O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 tetrahedra that share corners with two equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with eight equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with two equivalent O(4)Ca2Ta2 trigonal pyramids. In the fourth O site, O(2) is bonded to four equivalent Li(1) and one Ta(1) atom to form distorted OLi4Ta trigonal bipyramids that share  a cornercorner with one O(1)Ca2Ta2 tetrahedra, corners with four equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with four equivalent O(2)Li4Ta trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Li2CaTa2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.456
_cell_length_b   5.522
_cell_length_c   18.165
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   547.201
_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
  Li  Li0  1  0.749  0.492  0.987  1.0
  Li  Li1  1  0.251  0.508  0.487  1.0
  Li  Li2  1  0.249  0.008  0.487  1.0
  Li  Li3  1  0.751  0.992  0.987  1.0
  Li  Li4  1  0.251  0.508  0.013  1.0
  Li  Li5  1  0.749  0.492  0.513  1.0
  Li  Li6  1  0.751  0.992  0.513  1.0
  Li  Li7  1  0.249  0.008  0.013  1.0
  Ca  Ca8  1  0.998  0.207  0.250  1.0
  Ca  Ca9  1  0.002  0.793  0.750  1.0
  Ca  Ca10  1  0.498  0.293  0.750  1.0
  Ca  Ca11  1  0.502  0.707  0.250  1.0
  Ta  Ta12  1  0.498  0.759  0.637  1.0
  Ta  Ta13  1  0.502  0.241  0.137  1.0
  Ta  Ta14  1  0.998  0.741  0.137  1.0
  Ta  Ta15  1  0.002  0.259  0.637  1.0
  Ta  Ta16  1  0.502  0.241  0.363  1.0
  Ta  Ta17  1  0.498  0.759  0.863  1.0
  Ta  Ta18  1  0.002  0.259  0.863  1.0
  Ta  Ta19  1  0.998  0.741  0.363  1.0
  O  O20  1  0.079  0.771  0.250  1.0
  O  O21  1  0.921  0.229  0.750  1.0
  O  O22  1  0.579  0.729  0.750  1.0
  O  O23  1  0.421  0.271  0.250  1.0
  O  O24  1  0.049  0.257  0.965  1.0
  O  O25  1  0.951  0.743  0.465  1.0
  O  O26  1  0.549  0.243  0.465  1.0
  O  O27  1  0.451  0.757  0.965  1.0
  O  O28  1  0.951  0.743  0.035  1.0
  O  O29  1  0.049  0.257  0.535  1.0
  O  O30  1  0.451  0.757  0.535  1.0
  O  O31  1  0.549  0.243  0.035  1.0
  O  O32  1  0.208  0.042  0.369  1.0
  O  O33  1  0.792  0.958  0.869  1.0
  O  O34  1  0.708  0.458  0.869  1.0
  O  O35  1  0.292  0.542  0.369  1.0
  O  O36  1  0.792  0.958  0.631  1.0
  O  O37  1  0.208  0.042  0.131  1.0
  O  O38  1  0.292  0.542  0.131  1.0
  O  O39  1  0.708  0.458  0.631  1.0
  O  O40  1  0.219  0.530  0.665  1.0
  O  O41  1  0.781  0.470  0.165  1.0
  O  O42  1  0.719  0.970  0.165  1.0
  O  O43  1  0.281  0.030  0.665  1.0
  O  O44  1  0.781  0.470  0.335  1.0
  O  O45  1  0.219  0.530  0.835  1.0
  O  O46  1  0.281  0.030  0.835  1.0
  O  O47  1  0.719  0.970  0.335  1.0
[/CIF]
.
The material described by Li2CaTa2O7 crystallizes in the orthorhombic Pnma space group. Li(1) is bonded to one O(3) and four equivalent O(2) atoms to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Li(1)O5 trigonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with four equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 59°. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(4) atoms. Ta(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with five equivalent Ta(1)O6 octahedra, corners with two equivalent Li(1)O5 trigonal bipyramids, and edges with two equivalent Li(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 22-31°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 4-coordinate geometry to one Li(1), one Ca(1), and two equivalent Ta(1) atoms. In the second O site, O(4) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 trigonal pyramids that share corners with four equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids,  an edgeedge with one O(1)Ca2Ta2 tetrahedra, and edges with three equivalent O(4)Ca2Ta2 trigonal pyramids. In the third O site, O(1) is bonded to two equivalent Ca(1) and two equivalent Ta(1) atoms to form distorted OCa2Ta2 tetrahedra that share corners with two equivalent O(1)Ca2Ta2 tetrahedra, corners with two equivalent O(2)Li4Ta trigonal bipyramids, corners with eight equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with two equivalent O(4)Ca2Ta2 trigonal pyramids. In the fourth O site, O(2) is bonded to four equivalent Li(1) and one Ta(1) atom to form distorted OLi4Ta trigonal bipyramids that share  a cornercorner with one O(1)Ca2Ta2 tetrahedra, corners with four equivalent O(2)Li4Ta trigonal bipyramids, corners with two equivalent O(4)Ca2Ta2 trigonal pyramids, and edges with four equivalent O(2)Li4Ta trigonal bipyramids. is represented by the Crystallographic Information File (CIF) [CIF]
data_Li2CaTa2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.456
_cell_length_b   5.522
_cell_length_c   18.165
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   547.201
_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
  Li  Li0  1  0.749  0.492  0.987  1.0
  Li  Li1  1  0.251  0.508  0.487  1.0
  Li  Li2  1  0.249  0.008  0.487  1.0
  Li  Li3  1  0.751  0.992  0.987  1.0
  Li  Li4  1  0.251  0.508  0.013  1.0
  Li  Li5  1  0.749  0.492  0.513  1.0
  Li  Li6  1  0.751  0.992  0.513  1.0
  Li  Li7  1  0.249  0.008  0.013  1.0
  Ca  Ca8  1  0.998  0.207  0.250  1.0
  Ca  Ca9  1  0.002  0.793  0.750  1.0
  Ca  Ca10  1  0.498  0.293  0.750  1.0
  Ca  Ca11  1  0.502  0.707  0.250  1.0
  Ta  Ta12  1  0.498  0.759  0.637  1.0
  Ta  Ta13  1  0.502  0.241  0.137  1.0
  Ta  Ta14  1  0.998  0.741  0.137  1.0
  Ta  Ta15  1  0.002  0.259  0.637  1.0
  Ta  Ta16  1  0.502  0.241  0.363  1.0
  Ta  Ta17  1  0.498  0.759  0.863  1.0
  Ta  Ta18  1  0.002  0.259  0.863  1.0
  Ta  Ta19  1  0.998  0.741  0.363  1.0
  O  O20  1  0.079  0.771  0.250  1.0
  O  O21  1  0.921  0.229  0.750  1.0
  O  O22  1  0.579  0.729  0.750  1.0
  O  O23  1  0.421  0.271  0.250  1.0
  O  O24  1  0.049  0.257  0.965  1.0
  O  O25  1  0.951  0.743  0.465  1.0
  O  O26  1  0.549  0.243  0.465  1.0
  O  O27  1  0.451  0.757  0.965  1.0
  O  O28  1  0.951  0.743  0.035  1.0
  O  O29  1  0.049  0.257  0.535  1.0
  O  O30  1  0.451  0.757  0.535  1.0
  O  O31  1  0.549  0.243  0.035  1.0
  O  O32  1  0.208  0.042  0.369  1.0
  O  O33  1  0.792  0.958  0.869  1.0
  O  O34  1  0.708  0.458  0.869  1.0
  O  O35  1  0.292  0.542  0.369  1.0
  O  O36  1  0.792  0.958  0.631  1.0
  O  O37  1  0.208  0.042  0.131  1.0
  O  O38  1  0.292  0.542  0.131  1.0
  O  O39  1  0.708  0.458  0.631  1.0
  O  O40  1  0.219  0.530  0.665  1.0
  O  O41  1  0.781  0.470  0.165  1.0
  O  O42  1  0.719  0.970  0.165  1.0
  O  O43  1  0.281  0.030  0.665  1.0
  O  O44  1  0.781  0.470  0.335  1.0
  O  O45  1  0.219  0.530  0.835  1.0
  O  O46  1  0.281  0.030  0.835  1.0
  O  O47  1  0.719  0.970  0.335  1.0
[/CIF]
.