La2Hf2O7 crystallizes in the monoclinic P2_1 space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 9-coordinate geometry to one O(1), one O(11), one O(3), 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 8-coordinate geometry to one O(10), one O(14), one O(2), one O(5), one O(7), one O(8), and two equivalent O(12) atoms. There are four inequivalent Hf sites. In the first Hf site, Hf(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 HfO6 octahedra. The corner-sharing octahedral tilt angles range from 29-38°. In the second Hf site, Hf(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 HfO6 octahedra. The corner-sharing octahedral tilt angles range from 23-38°. In the third Hf site, Hf(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 HfO6 octahedra. The corner-sharing octahedral tilt angles range from 29-41°. In the fourth Hf site, Hf(4) is bonded to one O(11), one O(14), one O(4), one O(9), and two equivalent O(13) atoms to form corner-sharing HfO6 octahedra. The corner-sharing octahedral tilt angles range from 23-41°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one La(1), one La(3), one Hf(1), and one Hf(2) atom to form distorted OLa2Hf2 tetrahedra that share  a cornercorner with one O(11)La2Hf2 tetrahedra,  a cornercorner with one O(2)La3Hf tetrahedra,  a cornercorner with one O(5)La3Hf tetrahedra, corners with two equivalent O(9)La2Hf2 tetrahedra, and  an edgeedge with one O(11)La2Hf2 tetrahedra. In the second O site, O(2) is bonded to one La(4), two equivalent La(2), and one Hf(1) atom to form OLa3Hf tetrahedra that share  a cornercorner with one O(1)La2Hf2 tetrahedra, corners with two equivalent O(12)La3Hf tetrahedra, corners with two equivalent O(2)La3Hf tetrahedra,  an edgeedge with one O(12)La3Hf tetrahedra, and edges with three equivalent O(5)La3Hf tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Hf(1), and one Hf(3) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one La(1), one Hf(2), and one Hf(4) atom. In the fifth O site, O(5) is bonded to one La(4), two equivalent La(2), and one Hf(1) atom to form OLa3Hf tetrahedra that share  a cornercorner with one O(1)La2Hf2 tetrahedra, corners with two equivalent O(5)La3Hf tetrahedra, corners with four equivalent O(12)La3Hf tetrahedra, and edges with three equivalent O(2)La3Hf tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one La(3), two equivalent La(1), and two equivalent Hf(2) atoms. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one La(3), one La(4), one Hf(1), and one Hf(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one La(2), one La(4), and one Hf(3) atom. In the ninth O site, O(9) is bonded to one La(1), one La(3), one Hf(3), and one Hf(4) atom to form distorted OLa2Hf2 tetrahedra that share  a cornercorner with one O(11)La2Hf2 tetrahedra,  a cornercorner with one O(12)La3Hf tetrahedra, corners with two equivalent O(1)La2Hf2 tetrahedra, and  an edgeedge with one O(11)La2Hf2 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one La(3), one La(4), one Hf(1), and one Hf(3) atom. In the eleventh O site, O(11) is bonded to one La(1), one La(3), one Hf(2), and one Hf(4) atom to form a mixture of distorted corner and edge-sharing OLa2Hf2 tetrahedra. In the twelfth O site, O(12) is bonded to one La(2), two equivalent La(4), and one Hf(3) atom to form distorted OLa3Hf tetrahedra that share  a cornercorner with one O(9)La2Hf2 tetrahedra, corners with two equivalent O(12)La3Hf tetrahedra, corners with two equivalent O(2)La3Hf tetrahedra, corners with four equivalent O(5)La3Hf tetrahedra, and  an edgeedge with one O(2)La3Hf tetrahedra. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to one La(3), two equivalent La(1), and two equivalent Hf(4) atoms. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one La(3), one La(4), one Hf(3), and one Hf(4) atom.
La2Hf2O7 crystallizes in the monoclinic P2_1 space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 9-coordinate geometry to one O(1), one O(11), one O(3), one O(4), one O(9), two equivalent O(13), and two equivalent O(6) atoms. The La(1)-O(1) bond length is 2.40 Å. The La(1)-O(11) bond length is 2.50 Å. The La(1)-O(3) bond length is 2.83 Å. The La(1)-O(4) bond length is 2.44 Å. The La(1)-O(9) bond length is 2.38 Å. Both La(1)-O(13) bond lengths are 2.83 Å. There is one shorter (2.85 Å) and one longer (2.86 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 2.56 Å. The La(2)-O(3) bond length is 2.73 Å. The La(2)-O(8) bond length is 2.39 Å. There is one shorter (2.49 Å) and one longer (2.51 Å) La(2)-O(2) bond length. There is one shorter (2.45 Å) and one longer (2.53 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 2.63 Å. The La(3)-O(10) bond length is 2.54 Å. The La(3)-O(11) bond length is 2.50 Å. The La(3)-O(13) bond length is 2.47 Å. The La(3)-O(14) bond length is 2.60 Å. The La(3)-O(6) bond length is 2.48 Å. The La(3)-O(7) bond length is 2.61 Å. The La(3)-O(9) bond length is 2.59 Å. In the fourth La site, La(4) is bonded in a 8-coordinate geometry to one O(10), one O(14), one O(2), one O(5), one O(7), one O(8), and two equivalent O(12) atoms. The La(4)-O(10) bond length is 2.72 Å. The La(4)-O(14) bond length is 3.03 Å. The La(4)-O(2) bond length is 2.56 Å. The La(4)-O(5) bond length is 2.55 Å. The La(4)-O(7) bond length is 3.10 Å. The La(4)-O(8) bond length is 2.42 Å. There is one shorter (2.44 Å) and one longer (2.59 Å) La(4)-O(12) bond length. There are four inequivalent Hf sites. In the first Hf site, Hf(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 HfO6 octahedra. The corner-sharing octahedral tilt angles range from 29-38°. The Hf(1)-O(1) bond length is 2.14 Å. The Hf(1)-O(10) bond length is 2.12 Å. The Hf(1)-O(2) bond length is 2.04 Å. The Hf(1)-O(3) bond length is 2.07 Å. The Hf(1)-O(5) bond length is 2.01 Å. The Hf(1)-O(7) bond length is 2.19 Å. In the second Hf site, Hf(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 HfO6 octahedra. The corner-sharing octahedral tilt angles range from 23-38°. The Hf(2)-O(1) bond length is 2.05 Å. The Hf(2)-O(11) bond length is 2.11 Å. The Hf(2)-O(4) bond length is 2.08 Å. The Hf(2)-O(7) bond length is 2.00 Å. There is one shorter (2.11 Å) and one longer (2.23 Å) Hf(2)-O(6) bond length. In the third Hf site, Hf(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 HfO6 octahedra. The corner-sharing octahedral tilt angles range from 29-41°. The Hf(3)-O(10) bond length is 2.11 Å. The Hf(3)-O(12) bond length is 2.04 Å. The Hf(3)-O(14) bond length is 2.24 Å. The Hf(3)-O(3) bond length is 2.08 Å. The Hf(3)-O(8) bond length is 1.98 Å. The Hf(3)-O(9) bond length is 2.17 Å. In the fourth Hf site, Hf(4) is bonded to one O(11), one O(14), one O(4), one O(9), and two equivalent O(13) atoms to form corner-sharing HfO6 octahedra. The corner-sharing octahedral tilt angles range from 23-41°. The Hf(4)-O(11) bond length is 2.11 Å. The Hf(4)-O(14) bond length is 2.00 Å. The Hf(4)-O(4) bond length is 2.08 Å. The Hf(4)-O(9) bond length is 2.05 Å. There is one shorter (2.12 Å) and one longer (2.27 Å) Hf(4)-O(13) bond length. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one La(1), one La(3), one Hf(1), and one Hf(2) atom to form distorted OLa2Hf2 tetrahedra that share  a cornercorner with one O(11)La2Hf2 tetrahedra,  a cornercorner with one O(2)La3Hf tetrahedra,  a cornercorner with one O(5)La3Hf tetrahedra, corners with two equivalent O(9)La2Hf2 tetrahedra, and  an edgeedge with one O(11)La2Hf2 tetrahedra. In the second O site, O(2) is bonded to one La(4), two equivalent La(2), and one Hf(1) atom to form OLa3Hf tetrahedra that share  a cornercorner with one O(1)La2Hf2 tetrahedra, corners with two equivalent O(12)La3Hf tetrahedra, corners with two equivalent O(2)La3Hf tetrahedra,  an edgeedge with one O(12)La3Hf tetrahedra, and edges with three equivalent O(5)La3Hf tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one La(1), one La(2), one Hf(1), and one Hf(3) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one La(1), one Hf(2), and one Hf(4) atom. In the fifth O site, O(5) is bonded to one La(4), two equivalent La(2), and one Hf(1) atom to form OLa3Hf tetrahedra that share  a cornercorner with one O(1)La2Hf2 tetrahedra, corners with two equivalent O(5)La3Hf tetrahedra, corners with four equivalent O(12)La3Hf tetrahedra, and edges with three equivalent O(2)La3Hf tetrahedra. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one La(3), two equivalent La(1), and two equivalent Hf(2) atoms. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one La(3), one La(4), one Hf(1), and one Hf(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one La(2), one La(4), and one Hf(3) atom. In the ninth O site, O(9) is bonded to one La(1), one La(3), one Hf(3), and one Hf(4) atom to form distorted OLa2Hf2 tetrahedra that share  a cornercorner with one O(11)La2Hf2 tetrahedra,  a cornercorner with one O(12)La3Hf tetrahedra, corners with two equivalent O(1)La2Hf2 tetrahedra, and  an edgeedge with one O(11)La2Hf2 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one La(3), one La(4), one Hf(1), and one Hf(3) atom. In the eleventh O site, O(11) is bonded to one La(1), one La(3), one Hf(2), and one Hf(4) atom to form a mixture of distorted corner and edge-sharing OLa2Hf2 tetrahedra. In the twelfth O site, O(12) is bonded to one La(2), two equivalent La(4), and one Hf(3) atom to form distorted OLa3Hf tetrahedra that share  a cornercorner with one O(9)La2Hf2 tetrahedra, corners with two equivalent O(12)La3Hf tetrahedra, corners with two equivalent O(2)La3Hf tetrahedra, corners with four equivalent O(5)La3Hf tetrahedra, and  an edgeedge with one O(2)La3Hf tetrahedra. In the thirteenth O site, O(13) is bonded in a 5-coordinate geometry to one La(3), two equivalent La(1), and two equivalent Hf(4) atoms. In the fourteenth O site, O(14) is bonded in a 4-coordinate geometry to one La(3), one La(4), one Hf(3), and one Hf(4) atom.