Ca2Ta2CrO8 crystallizes in the triclinic P1 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(10), one O(14), one O(15), one O(16), and one O(9) atom. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(10), one O(13), one O(15), one O(16), and one O(9) atom. In the third Ca site, Ca(3) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(14), and one O(16) atom. In the fourth Ca site, Ca(4) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(13), one O(14), one O(15), and one O(9) atom. There are four inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(12), one O(16), one O(4), one O(5), and one O(9) atom to form distorted TaO6 octahedra that share corners with two equivalent Cr(1)O5 square pyramids, corners with two equivalent Cr(2)O5 square pyramids, and edges with two equivalent Ta(4)O6 octahedra. In the second Ta site, Ta(2) is bonded to one O(10), one O(11), one O(15), one O(2), one O(3), and one O(6) atom to form distorted TaO6 octahedra that share corners with two equivalent Cr(1)O5 square pyramids, corners with two equivalent Cr(2)O5 square pyramids, and edges with two equivalent Ta(3)O6 octahedra. In the third Ta site, Ta(3) is bonded to one O(10), one O(11), one O(14), one O(2), one O(3), and one O(7) atom to form distorted TaO6 octahedra that share  a cornercorner with one Cr(1)O5 square pyramid, corners with two equivalent Cr(2)O5 square pyramids, and edges with two equivalent Ta(2)O6 octahedra. In the fourth Ta site, Ta(4) is bonded to one O(1), one O(12), one O(13), one O(4), one O(8), and one O(9) atom to form distorted TaO6 octahedra that share  a cornercorner with one Cr(2)O5 square pyramid, corners with two equivalent Cr(1)O5 square pyramids, and edges with two equivalent Ta(1)O6 octahedra. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(4), one O(5), one O(6), and one O(8) atom to form distorted CrO5 square pyramids that share  a cornercorner with one Ta(3)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Ta(4)O6 octahedra, and  an edgeedge with one Cr(2)O5 square pyramid. The corner-sharing octahedral tilt angles range from 33-59°. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(5), one O(6), and one O(7) atom to form distorted CrO5 square pyramids that share  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, and  an edgeedge with one Cr(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 33-59°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(4), and one Cr(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ta(2), one Ta(3), and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ta(2), one Ta(3), and one Cr(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(4), and one Cr(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ta(1), one Cr(1), and one Cr(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ta(2), one Cr(1), and one Cr(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ta(3) and one Cr(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Ta(4) and one Cr(1) atom. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), one Ta(1), and one Ta(4) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), one Ta(2), and one Ta(3) atom. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Ca(3), one Ca(4), one Ta(2), and one Ta(3) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one Ca(3), one Ca(4), one Ta(1), and one Ta(4) atom. In the thirteenth O site, O(13) is bonded to one Ca(2), one Ca(3), one Ca(4), and one Ta(4) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the fourteenth O site, O(14) is bonded to one Ca(1), one Ca(3), one Ca(4), and one Ta(3) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the fifteenth O site, O(15) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the sixteenth O site, O(16) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Ta(1) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids.
Ca2Ta2CrO8 crystallizes in the triclinic P1 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(10), one O(14), one O(15), one O(16), and one O(9) atom. The Ca(1)-O(10) bond length is 2.25 Å. The Ca(1)-O(14) bond length is 2.24 Å. The Ca(1)-O(15) bond length is 2.24 Å. The Ca(1)-O(16) bond length is 2.37 Å. The Ca(1)-O(9) bond length is 2.57 Å. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(10), one O(13), one O(15), one O(16), and one O(9) atom. The Ca(2)-O(10) bond length is 2.57 Å. The Ca(2)-O(13) bond length is 2.24 Å. The Ca(2)-O(15) bond length is 2.37 Å. The Ca(2)-O(16) bond length is 2.24 Å. The Ca(2)-O(9) bond length is 2.25 Å. In the third Ca site, Ca(3) is bonded in a 6-coordinate geometry to one O(10), one O(11), one O(12), one O(13), one O(14), and one O(16) atom. The Ca(3)-O(10) bond length is 2.78 Å. The Ca(3)-O(11) bond length is 2.56 Å. The Ca(3)-O(12) bond length is 2.25 Å. The Ca(3)-O(13) bond length is 2.25 Å. The Ca(3)-O(14) bond length is 2.37 Å. The Ca(3)-O(16) bond length is 2.25 Å. In the fourth Ca site, Ca(4) is bonded in a 6-coordinate geometry to one O(11), one O(12), one O(13), one O(14), one O(15), and one O(9) atom. The Ca(4)-O(11) bond length is 2.25 Å. The Ca(4)-O(12) bond length is 2.56 Å. The Ca(4)-O(13) bond length is 2.37 Å. The Ca(4)-O(14) bond length is 2.25 Å. The Ca(4)-O(15) bond length is 2.25 Å. The Ca(4)-O(9) bond length is 2.78 Å. There are four inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(1), one O(12), one O(16), one O(4), one O(5), and one O(9) atom to form distorted TaO6 octahedra that share corners with two equivalent Cr(1)O5 square pyramids, corners with two equivalent Cr(2)O5 square pyramids, and edges with two equivalent Ta(4)O6 octahedra. The Ta(1)-O(1) bond length is 2.03 Å. The Ta(1)-O(12) bond length is 2.23 Å. The Ta(1)-O(16) bond length is 1.94 Å. The Ta(1)-O(4) bond length is 2.05 Å. The Ta(1)-O(5) bond length is 1.91 Å. The Ta(1)-O(9) bond length is 2.03 Å. In the second Ta site, Ta(2) is bonded to one O(10), one O(11), one O(15), one O(2), one O(3), and one O(6) atom to form distorted TaO6 octahedra that share corners with two equivalent Cr(1)O5 square pyramids, corners with two equivalent Cr(2)O5 square pyramids, and edges with two equivalent Ta(3)O6 octahedra. The Ta(2)-O(10) bond length is 2.03 Å. The Ta(2)-O(11) bond length is 2.24 Å. The Ta(2)-O(15) bond length is 1.94 Å. The Ta(2)-O(2) bond length is 2.03 Å. The Ta(2)-O(3) bond length is 2.05 Å. The Ta(2)-O(6) bond length is 1.91 Å. In the third Ta site, Ta(3) is bonded to one O(10), one O(11), one O(14), one O(2), one O(3), and one O(7) atom to form distorted TaO6 octahedra that share  a cornercorner with one Cr(1)O5 square pyramid, corners with two equivalent Cr(2)O5 square pyramids, and edges with two equivalent Ta(2)O6 octahedra. The Ta(3)-O(10) bond length is 2.30 Å. The Ta(3)-O(11) bond length is 2.05 Å. The Ta(3)-O(14) bond length is 1.93 Å. The Ta(3)-O(2) bond length is 2.12 Å. The Ta(3)-O(3) bond length is 1.98 Å. The Ta(3)-O(7) bond length is 1.85 Å. In the fourth Ta site, Ta(4) is bonded to one O(1), one O(12), one O(13), one O(4), one O(8), and one O(9) atom to form distorted TaO6 octahedra that share  a cornercorner with one Cr(2)O5 square pyramid, corners with two equivalent Cr(1)O5 square pyramids, and edges with two equivalent Ta(1)O6 octahedra. The Ta(4)-O(1) bond length is 2.11 Å. The Ta(4)-O(12) bond length is 2.05 Å. The Ta(4)-O(13) bond length is 1.93 Å. The Ta(4)-O(4) bond length is 1.98 Å. The Ta(4)-O(8) bond length is 1.85 Å. The Ta(4)-O(9) bond length is 2.30 Å. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(4), one O(5), one O(6), and one O(8) atom to form distorted CrO5 square pyramids that share  a cornercorner with one Ta(3)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Ta(4)O6 octahedra, and  an edgeedge with one Cr(2)O5 square pyramid. The corner-sharing octahedral tilt angles range from 33-59°. The Cr(1)-O(2) bond length is 2.13 Å. The Cr(1)-O(4) bond length is 2.55 Å. The Cr(1)-O(5) bond length is 2.17 Å. The Cr(1)-O(6) bond length is 2.11 Å. The Cr(1)-O(8) bond length is 2.04 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(5), one O(6), and one O(7) atom to form distorted CrO5 square pyramids that share  a cornercorner with one Ta(4)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with two equivalent Ta(2)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, and  an edgeedge with one Cr(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 33-59°. The Cr(2)-O(1) bond length is 2.13 Å. The Cr(2)-O(3) bond length is 2.54 Å. The Cr(2)-O(5) bond length is 2.11 Å. The Cr(2)-O(6) bond length is 2.18 Å. The Cr(2)-O(7) bond length is 2.05 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(4), and one Cr(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ta(2), one Ta(3), and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ta(2), one Ta(3), and one Cr(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ta(1), one Ta(4), and one Cr(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Ta(1), one Cr(1), and one Cr(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ta(2), one Cr(1), and one Cr(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ta(3) and one Cr(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Ta(4) and one Cr(1) atom. In the ninth O site, O(9) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), one Ta(1), and one Ta(4) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), one Ta(2), and one Ta(3) atom. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Ca(3), one Ca(4), one Ta(2), and one Ta(3) atom. In the twelfth O site, O(12) is bonded in a 4-coordinate geometry to one Ca(3), one Ca(4), one Ta(1), and one Ta(4) atom. In the thirteenth O site, O(13) is bonded to one Ca(2), one Ca(3), one Ca(4), and one Ta(4) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the fourteenth O site, O(14) is bonded to one Ca(1), one Ca(3), one Ca(4), and one Ta(3) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the fifteenth O site, O(15) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Ta(2) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids. In the sixteenth O site, O(16) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Ta(1) atom to form a mixture of distorted edge and corner-sharing OCa3Ta trigonal pyramids.