Ca4Zr3TaO12 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(4), one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(6), two equivalent O(4), and two equivalent O(5) atoms. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing ZrO6 octahedra. The corner-sharing octahedral tilt angles are 35°. In the second Zr site, Zr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form ZrO6 octahedra that share corners with two equivalent Zr(1)O6 octahedra and corners with four equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 31-35°. In the third Zr site, Zr(3) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form ZrO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra and corners with four equivalent Zr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 33-35°. Ta(1) is bonded to two equivalent O(2), two equivalent O(5), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Zr(3)O6 octahedra and corners with four equivalent Zr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 31-33°. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(2), one Zr(1), and one Zr(2) atom to form distorted OCa2Zr2 tetrahedra that share corners with two equivalent O(1)Ca2Zr2 tetrahedra and corners with two equivalent O(6)Ca2ZrTa tetrahedra. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Zr(2), and one Ta(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Zr(1), and one Zr(3) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Zr(1), and one Zr(3) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Zr(2), and one Ta(1) atom. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(2), one Zr(3), and one Ta(1) atom to form distorted OCa2ZrTa tetrahedra that share corners with two equivalent O(1)Ca2Zr2 tetrahedra and corners with two equivalent O(6)Ca2ZrTa tetrahedra.
Ca4Zr3TaO12 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one O(1), one O(4), one O(5), one O(6), two equivalent O(2), and two equivalent O(3) atoms. The Ca(1)-O(1) bond length is 2.34 Å. The Ca(1)-O(4) bond length is 2.72 Å. The Ca(1)-O(5) bond length is 2.66 Å. The Ca(1)-O(6) bond length is 2.47 Å. There is one shorter (2.43 Å) and one longer (2.84 Å) Ca(1)-O(2) bond length. There is one shorter (2.36 Å) and one longer (2.87 Å) Ca(1)-O(3) bond length. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(6), two equivalent O(4), and two equivalent O(5) atoms. The Ca(2)-O(1) bond length is 2.47 Å. The Ca(2)-O(2) bond length is 2.67 Å. The Ca(2)-O(3) bond length is 2.73 Å. The Ca(2)-O(6) bond length is 2.37 Å. There is one shorter (2.35 Å) and one longer (2.87 Å) Ca(2)-O(4) bond length. There is one shorter (2.42 Å) and one longer (2.83 Å) Ca(2)-O(5) bond length. There are three inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing ZrO6 octahedra. The corner-sharing octahedral tilt angles are 35°. Both Zr(1)-O(1) bond lengths are 2.13 Å. Both Zr(1)-O(3) bond lengths are 2.12 Å. Both Zr(1)-O(4) bond lengths are 2.13 Å. In the second Zr site, Zr(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form ZrO6 octahedra that share corners with two equivalent Zr(1)O6 octahedra and corners with four equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 31-35°. Both Zr(2)-O(1) bond lengths are 2.11 Å. Both Zr(2)-O(2) bond lengths are 2.16 Å. Both Zr(2)-O(5) bond lengths are 2.16 Å. In the third Zr site, Zr(3) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form ZrO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra and corners with four equivalent Zr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 33-35°. Both Zr(3)-O(3) bond lengths are 2.11 Å. Both Zr(3)-O(4) bond lengths are 2.12 Å. Both Zr(3)-O(6) bond lengths are 2.16 Å. Ta(1) is bonded to two equivalent O(2), two equivalent O(5), and two equivalent O(6) atoms to form TaO6 octahedra that share corners with two equivalent Zr(3)O6 octahedra and corners with four equivalent Zr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 31-33°. Both Ta(1)-O(2) bond lengths are 2.04 Å. Both Ta(1)-O(5) bond lengths are 2.05 Å. Both Ta(1)-O(6) bond lengths are 2.04 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(2), one Zr(1), and one Zr(2) atom to form distorted OCa2Zr2 tetrahedra that share corners with two equivalent O(1)Ca2Zr2 tetrahedra and corners with two equivalent O(6)Ca2ZrTa tetrahedra. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Zr(2), and one Ta(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Zr(1), and one Zr(3) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Zr(1), and one Zr(3) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Zr(2), and one Ta(1) atom. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(2), one Zr(3), and one Ta(1) atom to form distorted OCa2ZrTa tetrahedra that share corners with two equivalent O(1)Ca2Zr2 tetrahedra and corners with two equivalent O(6)Ca2ZrTa tetrahedra.