Gd2Ce8O19 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal P-4m2 space group. Gd(1) is bonded in a 6-coordinate geometry to two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a body-centered cubic geometry to two equivalent O(4), two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(9) atoms. In the third Ce site, Ce(3) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(10), two equivalent O(2), and two equivalent O(9) atoms. In the fourth Ce site, Ce(4) is bonded in a body-centered cubic geometry to two equivalent O(10), two equivalent O(11), two equivalent O(2), and two equivalent O(3) atoms. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ce(2) and two equivalent Ce(3) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the second O site, O(2) is bonded to two equivalent Ce(3) and two equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the third O site, O(3) is bonded to four equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(7)Ce2Gd2 tetrahedra, corners with two equivalent O(9)Ce4 tetrahedra, corners with four equivalent O(6)Ce2Gd2 tetrahedra, corners with four equivalent O(1)Ce4 tetrahedra, corners with four equivalent O(4)Ce4 tetrahedra,  an edgeedge with one O(7)Ce2Gd2 tetrahedra,  an edgeedge with one O(9)Ce4 tetrahedra, and edges with four equivalent O(5)Ce4 tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(6)Ce2Gd2 tetrahedra, corners with two equivalent O(1)Ce4 tetrahedra, corners with four equivalent O(7)Ce2Gd2 tetrahedra, corners with four equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(9)Ce4 tetrahedra,  an edgeedge with one O(6)Ce2Gd2 tetrahedra,  an edgeedge with one O(1)Ce4 tetrahedra, and edges with four equivalent O(4)Ce4 tetrahedra. In the sixth O site, O(6) is bonded to two equivalent Gd(1) and two equivalent Ce(1) atoms to form OCe2Gd2 tetrahedra that share corners with two equivalent O(5)Ce4 tetrahedra, corners with two equivalent O(8)Gd4 tetrahedra, corners with four equivalent O(6)Ce2Gd2 tetrahedra, corners with four equivalent O(4)Ce4 tetrahedra,  an edgeedge with one O(5)Ce4 tetrahedra,  an edgeedge with one O(8)Gd4 tetrahedra, and edges with four equivalent O(7)Ce2Gd2 tetrahedra. In the seventh O site, O(7) is bonded to two equivalent Gd(1) and two equivalent Ce(1) atoms to form OCe2Gd2 tetrahedra that share corners with two equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(7)Ce2Gd2 tetrahedra, corners with four equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(8)Gd4 tetrahedra,  an edgeedge with one O(4)Ce4 tetrahedra, and edges with four equivalent O(6)Ce2Gd2 tetrahedra. In the eighth O site, O(8) is bonded to four equivalent Gd(1) atoms to form OGd4 tetrahedra that share corners with four equivalent O(6)Ce2Gd2 tetrahedra, corners with four equivalent O(8)Gd4 tetrahedra, corners with eight equivalent O(7)Ce2Gd2 tetrahedra, and edges with two equivalent O(6)Ce2Gd2 tetrahedra. In the ninth O site, O(9) is bonded to two equivalent Ce(2) and two equivalent Ce(3) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the tenth O site, O(10) is bonded to two equivalent Ce(3) and two equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the eleventh O site, O(11) is bonded to four equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra.
Gd2Ce8O19 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal P-4m2 space group. Gd(1) is bonded in a 6-coordinate geometry to two equivalent O(6), two equivalent O(7), and two equivalent O(8) atoms. Both Gd(1)-O(6) bond lengths are 2.34 Å. Both Gd(1)-O(7) bond lengths are 2.20 Å. Both Gd(1)-O(8) bond lengths are 2.47 Å. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a body-centered cubic geometry to two equivalent O(4), two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms. Both Ce(1)-O(4) bond lengths are 2.34 Å. Both Ce(1)-O(5) bond lengths are 2.39 Å. Both Ce(1)-O(6) bond lengths are 2.30 Å. Both Ce(1)-O(7) bond lengths are 2.45 Å. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(9) atoms. Both Ce(2)-O(1) bond lengths are 2.37 Å. Both Ce(2)-O(4) bond lengths are 2.39 Å. Both Ce(2)-O(5) bond lengths are 2.34 Å. Both Ce(2)-O(9) bond lengths are 2.37 Å. In the third Ce site, Ce(3) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(10), two equivalent O(2), and two equivalent O(9) atoms. Both Ce(3)-O(1) bond lengths are 2.37 Å. Both Ce(3)-O(10) bond lengths are 2.36 Å. Both Ce(3)-O(2) bond lengths are 2.37 Å. Both Ce(3)-O(9) bond lengths are 2.37 Å. In the fourth Ce site, Ce(4) is bonded in a body-centered cubic geometry to two equivalent O(10), two equivalent O(11), two equivalent O(2), and two equivalent O(3) atoms. Both Ce(4)-O(10) bond lengths are 2.37 Å. Both Ce(4)-O(11) bond lengths are 2.36 Å. Both Ce(4)-O(2) bond lengths are 2.36 Å. Both Ce(4)-O(3) bond lengths are 2.36 Å. There are eleven inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ce(2) and two equivalent Ce(3) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the second O site, O(2) is bonded to two equivalent Ce(3) and two equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the third O site, O(3) is bonded to four equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(7)Ce2Gd2 tetrahedra, corners with two equivalent O(9)Ce4 tetrahedra, corners with four equivalent O(6)Ce2Gd2 tetrahedra, corners with four equivalent O(1)Ce4 tetrahedra, corners with four equivalent O(4)Ce4 tetrahedra,  an edgeedge with one O(7)Ce2Gd2 tetrahedra,  an edgeedge with one O(9)Ce4 tetrahedra, and edges with four equivalent O(5)Ce4 tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(6)Ce2Gd2 tetrahedra, corners with two equivalent O(1)Ce4 tetrahedra, corners with four equivalent O(7)Ce2Gd2 tetrahedra, corners with four equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(9)Ce4 tetrahedra,  an edgeedge with one O(6)Ce2Gd2 tetrahedra,  an edgeedge with one O(1)Ce4 tetrahedra, and edges with four equivalent O(4)Ce4 tetrahedra. In the sixth O site, O(6) is bonded to two equivalent Gd(1) and two equivalent Ce(1) atoms to form OCe2Gd2 tetrahedra that share corners with two equivalent O(5)Ce4 tetrahedra, corners with two equivalent O(8)Gd4 tetrahedra, corners with four equivalent O(6)Ce2Gd2 tetrahedra, corners with four equivalent O(4)Ce4 tetrahedra,  an edgeedge with one O(5)Ce4 tetrahedra,  an edgeedge with one O(8)Gd4 tetrahedra, and edges with four equivalent O(7)Ce2Gd2 tetrahedra. In the seventh O site, O(7) is bonded to two equivalent Gd(1) and two equivalent Ce(1) atoms to form OCe2Gd2 tetrahedra that share corners with two equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(7)Ce2Gd2 tetrahedra, corners with four equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(8)Gd4 tetrahedra,  an edgeedge with one O(4)Ce4 tetrahedra, and edges with four equivalent O(6)Ce2Gd2 tetrahedra. In the eighth O site, O(8) is bonded to four equivalent Gd(1) atoms to form OGd4 tetrahedra that share corners with four equivalent O(6)Ce2Gd2 tetrahedra, corners with four equivalent O(8)Gd4 tetrahedra, corners with eight equivalent O(7)Ce2Gd2 tetrahedra, and edges with two equivalent O(6)Ce2Gd2 tetrahedra. In the ninth O site, O(9) is bonded to two equivalent Ce(2) and two equivalent Ce(3) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the tenth O site, O(10) is bonded to two equivalent Ce(3) and two equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra. In the eleventh O site, O(11) is bonded to four equivalent Ce(4) atoms to form a mixture of edge and corner-sharing OCe4 tetrahedra.