La2Ce2O7 crystallizes in the monoclinic P2_1 space group. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(5), and one O(7) atom to form corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 39-48°. In the second Ce site, Ce(2) is bonded to one O(1), one O(11), one O(4), one O(7), and two equivalent O(6) atoms to form corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 34-48°. In the third Ce site, Ce(3) is bonded to one O(10), one O(12), one O(14), one O(3), one O(8), and one O(9) atom to form corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. In the fourth Ce site, Ce(4) is bonded to one O(11), one O(14), one O(4), one O(9), and two equivalent O(13) atoms to form distorted corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 31-51°. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 4-coordinate geometry to one O(1), one O(11), one O(4), one O(9), two equivalent O(13), and two equivalent O(6) atoms. In the second La site, La(2) is bonded in a 7-coordinate geometry to one O(12), one O(3), one O(8), two equivalent O(2), and two equivalent O(5) atoms. In the third La site, La(3) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(13), one O(14), one O(6), one O(7), and one O(9) atom. In the fourth La site, La(4) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(5), one O(8), and two equivalent O(12) atoms. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one Ce(1), one Ce(2), one La(1), and one La(3) atom to form distorted OLa2Ce2 tetrahedra that share  a cornercorner with one O(11)La2Ce2 tetrahedra,  a cornercorner with one O(2)La3Ce tetrahedra,  a cornercorner with one O(5)La3Ce tetrahedra, corners with two equivalent O(9)La2Ce2 tetrahedra, and  an edgeedge with one O(11)La2Ce2 tetrahedra. In the second O site, O(2) is bonded to one Ce(1), one La(4), and two equivalent La(2) atoms to form OLa3Ce tetrahedra that share  a cornercorner with one O(1)La2Ce2 tetrahedra, corners with two equivalent O(12)La3Ce tetrahedra, corners with two equivalent O(2)La3Ce tetrahedra,  an edgeedge with one O(12)La3Ce tetrahedra, and edges with three equivalent O(5)La3Ce tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(3), and one La(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ce(2), one Ce(4), and one La(1) atom. In the fifth O site, O(5) is bonded to one Ce(1), one La(4), and two equivalent La(2) atoms to form distorted OLa3Ce tetrahedra that share  a cornercorner with one O(1)La2Ce2 tetrahedra, corners with two equivalent O(5)La3Ce tetrahedra, corners with four equivalent O(12)La3Ce tetrahedra, and edges with three equivalent O(2)La3Ce tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to two equivalent Ce(2), one La(3), and two equivalent La(1) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(2), and one La(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Ce(3), one La(2), and one La(4) atom. In the ninth O site, O(9) is bonded to one Ce(3), one Ce(4), one La(1), and one La(3) atom to form distorted OLa2Ce2 tetrahedra that share  a cornercorner with one O(11)La2Ce2 tetrahedra,  a cornercorner with one O(12)La3Ce tetrahedra, corners with two equivalent O(1)La2Ce2 tetrahedra, and  an edgeedge with one O(11)La2Ce2 tetrahedra. In the tenth O site, O(10) is bonded in a distorted see-saw-like geometry to one Ce(1), one Ce(3), one La(3), and one La(4) atom. In the eleventh O site, O(11) is bonded to one Ce(2), one Ce(4), one La(1), and one La(3) atom to form a mixture of distorted corner and edge-sharing OLa2Ce2 tetrahedra. In the twelfth O site, O(12) is bonded to one Ce(3), one La(2), and two equivalent La(4) atoms to form distorted OLa3Ce tetrahedra that share  a cornercorner with one O(9)La2Ce2 tetrahedra, corners with two equivalent O(12)La3Ce tetrahedra, corners with two equivalent O(2)La3Ce tetrahedra, corners with four equivalent O(5)La3Ce tetrahedra, and  an edgeedge with one O(2)La3Ce tetrahedra. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to two equivalent Ce(4), one La(3), and two equivalent La(1) atoms. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Ce(3), one Ce(4), and one La(3) atom.
La2Ce2O7 crystallizes in the monoclinic P2_1 space group. There are four inequivalent Ce sites. In the first Ce site, Ce(1) is bonded to one O(1), one O(10), one O(2), one O(3), one O(5), and one O(7) atom to form corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 39-48°. The Ce(1)-O(1) bond length is 2.33 Å. The Ce(1)-O(10) bond length is 2.32 Å. The Ce(1)-O(2) bond length is 2.27 Å. The Ce(1)-O(3) bond length is 2.22 Å. The Ce(1)-O(5) bond length is 2.17 Å. The Ce(1)-O(7) bond length is 2.30 Å. In the second Ce site, Ce(2) is bonded to one O(1), one O(11), one O(4), one O(7), and two equivalent O(6) atoms to form corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 34-48°. The Ce(2)-O(1) bond length is 2.22 Å. The Ce(2)-O(11) bond length is 2.30 Å. The Ce(2)-O(4) bond length is 2.24 Å. The Ce(2)-O(7) bond length is 2.16 Å. There is one shorter (2.29 Å) and one longer (2.41 Å) Ce(2)-O(6) bond length. In the third Ce site, Ce(3) is bonded to one O(10), one O(12), one O(14), one O(3), one O(8), and one O(9) atom to form corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 38-51°. The Ce(3)-O(10) bond length is 2.32 Å. The Ce(3)-O(12) bond length is 2.28 Å. The Ce(3)-O(14) bond length is 2.32 Å. The Ce(3)-O(3) bond length is 2.21 Å. The Ce(3)-O(8) bond length is 2.16 Å. The Ce(3)-O(9) bond length is 2.38 Å. In the fourth Ce site, Ce(4) is bonded to one O(11), one O(14), one O(4), one O(9), and two equivalent O(13) atoms to form distorted corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles range from 31-51°. The Ce(4)-O(11) bond length is 2.29 Å. The Ce(4)-O(14) bond length is 2.17 Å. The Ce(4)-O(4) bond length is 2.23 Å. The Ce(4)-O(9) bond length is 2.21 Å. There is one shorter (2.29 Å) and one longer (2.50 Å) Ce(4)-O(13) bond length. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 4-coordinate geometry to one O(1), one O(11), one O(4), one O(9), two equivalent O(13), and two equivalent O(6) atoms. The La(1)-O(1) bond length is 2.39 Å. The La(1)-O(11) bond length is 2.46 Å. The La(1)-O(4) bond length is 2.37 Å. The La(1)-O(9) bond length is 2.37 Å. There is one shorter (2.75 Å) and one longer (3.03 Å) La(1)-O(13) bond length. There is one shorter (2.77 Å) and one longer (3.14 Å) La(1)-O(6) bond length. In the second La site, La(2) is bonded in a 7-coordinate geometry to one O(12), one O(3), one O(8), two equivalent O(2), and two equivalent O(5) atoms. The La(2)-O(12) bond length is 2.68 Å. The La(2)-O(3) bond length is 2.65 Å. The La(2)-O(8) bond length is 2.44 Å. There is one shorter (2.46 Å) and one longer (2.61 Å) La(2)-O(2) bond length. There is one shorter (2.48 Å) and one longer (2.66 Å) La(2)-O(5) bond length. In the third La site, La(3) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(13), one O(14), one O(6), one O(7), and one O(9) atom. The La(3)-O(1) bond length is 2.77 Å. The La(3)-O(10) bond length is 2.72 Å. The La(3)-O(11) bond length is 2.46 Å. The La(3)-O(13) bond length is 2.45 Å. The La(3)-O(14) bond length is 2.54 Å. The La(3)-O(6) bond length is 2.46 Å. The La(3)-O(7) bond length is 2.60 Å. The La(3)-O(9) bond length is 2.69 Å. In the fourth La site, La(4) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(5), one O(8), and two equivalent O(12) atoms. The La(4)-O(10) bond length is 2.55 Å. The La(4)-O(2) bond length is 2.60 Å. The La(4)-O(5) bond length is 2.72 Å. The La(4)-O(8) bond length is 2.47 Å. There is one shorter (2.35 Å) and one longer (2.77 Å) La(4)-O(12) bond length. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one Ce(1), one Ce(2), one La(1), and one La(3) atom to form distorted OLa2Ce2 tetrahedra that share  a cornercorner with one O(11)La2Ce2 tetrahedra,  a cornercorner with one O(2)La3Ce tetrahedra,  a cornercorner with one O(5)La3Ce tetrahedra, corners with two equivalent O(9)La2Ce2 tetrahedra, and  an edgeedge with one O(11)La2Ce2 tetrahedra. In the second O site, O(2) is bonded to one Ce(1), one La(4), and two equivalent La(2) atoms to form OLa3Ce tetrahedra that share  a cornercorner with one O(1)La2Ce2 tetrahedra, corners with two equivalent O(12)La3Ce tetrahedra, corners with two equivalent O(2)La3Ce tetrahedra,  an edgeedge with one O(12)La3Ce tetrahedra, and edges with three equivalent O(5)La3Ce tetrahedra. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(3), and one La(2) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ce(2), one Ce(4), and one La(1) atom. In the fifth O site, O(5) is bonded to one Ce(1), one La(4), and two equivalent La(2) atoms to form distorted OLa3Ce tetrahedra that share  a cornercorner with one O(1)La2Ce2 tetrahedra, corners with two equivalent O(5)La3Ce tetrahedra, corners with four equivalent O(12)La3Ce tetrahedra, and edges with three equivalent O(2)La3Ce tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to two equivalent Ce(2), one La(3), and two equivalent La(1) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ce(1), one Ce(2), and one La(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Ce(3), one La(2), and one La(4) atom. In the ninth O site, O(9) is bonded to one Ce(3), one Ce(4), one La(1), and one La(3) atom to form distorted OLa2Ce2 tetrahedra that share  a cornercorner with one O(11)La2Ce2 tetrahedra,  a cornercorner with one O(12)La3Ce tetrahedra, corners with two equivalent O(1)La2Ce2 tetrahedra, and  an edgeedge with one O(11)La2Ce2 tetrahedra. In the tenth O site, O(10) is bonded in a distorted see-saw-like geometry to one Ce(1), one Ce(3), one La(3), and one La(4) atom. In the eleventh O site, O(11) is bonded to one Ce(2), one Ce(4), one La(1), and one La(3) atom to form a mixture of distorted corner and edge-sharing OLa2Ce2 tetrahedra. In the twelfth O site, O(12) is bonded to one Ce(3), one La(2), and two equivalent La(4) atoms to form distorted OLa3Ce tetrahedra that share  a cornercorner with one O(9)La2Ce2 tetrahedra, corners with two equivalent O(12)La3Ce tetrahedra, corners with two equivalent O(2)La3Ce tetrahedra, corners with four equivalent O(5)La3Ce tetrahedra, and  an edgeedge with one O(2)La3Ce tetrahedra. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to two equivalent Ce(4), one La(3), and two equivalent La(1) atoms. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Ce(3), one Ce(4), and one La(3) atom.