La2Si2O7 crystallizes in the triclinic P-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(13), one O(14), one O(6), one O(7), one O(9), and two equivalent O(8) atoms. In the second La site, La(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(12), one O(14), one O(2), one O(8), and one O(9) atom. In the third La site, La(3) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(2), one O(3), one O(6), one O(7), and two equivalent O(5) atoms. In the fourth La site, La(4) is bonded in a 7-coordinate geometry to one O(1), one O(14), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(12), one O(13), one O(14), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(10), one O(11), one O(12), and one O(9) atom to form corner-sharing SiO4 tetrahedra. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one La(1), one La(2), one La(4), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one La(2), one La(3), one La(4), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one La(3), one La(4), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one La(4), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one La(4), two equivalent La(3), and one Si(2) atom to form distorted edge-sharing OLa3Si tetrahedra. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one La(1), one La(3), one La(4), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one La(1), one La(3), and one Si(2) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one La(2), two equivalent La(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one La(1), one La(2), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one La(2), one La(3), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 1-coordinate geometry to one La(1), one La(2), one La(3), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a distorted bent 120 degrees geometry to one La(2), one Si(3), and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a distorted bent 150 degrees geometry to one La(1) and one Si(3) atom. In the fourteenth O site, O(14) is bonded in a 1-coordinate geometry to one La(1), one La(2), one La(4), and one Si(3) atom.
La2Si2O7 crystallizes in the triclinic P-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(13), one O(14), one O(6), one O(7), one O(9), and two equivalent O(8) atoms. The La(1)-O(1) bond length is 2.77 Å. The La(1)-O(11) bond length is 2.53 Å. The La(1)-O(13) bond length is 2.39 Å. The La(1)-O(14) bond length is 2.94 Å. The La(1)-O(6) bond length is 2.79 Å. The La(1)-O(7) bond length is 2.73 Å. The La(1)-O(9) bond length is 2.45 Å. There is one shorter (2.62 Å) and one longer (2.67 Å) La(1)-O(8) bond length. In the second La site, La(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(11), one O(12), one O(14), one O(2), one O(8), and one O(9) atom. The La(2)-O(1) bond length is 2.75 Å. The La(2)-O(10) bond length is 2.48 Å. The La(2)-O(11) bond length is 2.54 Å. The La(2)-O(12) bond length is 2.84 Å. The La(2)-O(14) bond length is 2.60 Å. The La(2)-O(2) bond length is 2.70 Å. The La(2)-O(8) bond length is 2.48 Å. The La(2)-O(9) bond length is 2.43 Å. In the third La site, La(3) is bonded in a 8-coordinate geometry to one O(10), one O(11), one O(2), one O(3), one O(6), one O(7), and two equivalent O(5) atoms. The La(3)-O(10) bond length is 2.37 Å. The La(3)-O(11) bond length is 2.99 Å. The La(3)-O(2) bond length is 2.67 Å. The La(3)-O(3) bond length is 2.41 Å. The La(3)-O(6) bond length is 2.70 Å. The La(3)-O(7) bond length is 2.38 Å. There is one shorter (2.55 Å) and one longer (2.60 Å) La(3)-O(5) bond length. In the fourth La site, La(4) is bonded in a 7-coordinate geometry to one O(1), one O(14), one O(2), one O(3), one O(4), one O(5), and one O(6) atom. The La(4)-O(1) bond length is 2.50 Å. The La(4)-O(14) bond length is 2.41 Å. The La(4)-O(2) bond length is 2.47 Å. The La(4)-O(3) bond length is 2.47 Å. The La(4)-O(4) bond length is 2.75 Å. The La(4)-O(5) bond length is 2.52 Å. The La(4)-O(6) bond length is 2.52 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(4) bond length is 1.69 Å. In the second Si site, Si(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(4) bond length is 1.68 Å. The Si(2)-O(5) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.65 Å. The Si(2)-O(7) bond length is 1.61 Å. In the third Si site, Si(3) is bonded to one O(12), one O(13), one O(14), and one O(8) atom to form corner-sharing SiO4 tetrahedra. The Si(3)-O(12) bond length is 1.67 Å. The Si(3)-O(13) bond length is 1.61 Å. The Si(3)-O(14) bond length is 1.66 Å. The Si(3)-O(8) bond length is 1.65 Å. In the fourth Si site, Si(4) is bonded to one O(10), one O(11), one O(12), and one O(9) atom to form corner-sharing SiO4 tetrahedra. The Si(4)-O(10) bond length is 1.64 Å. The Si(4)-O(11) bond length is 1.64 Å. The Si(4)-O(12) bond length is 1.67 Å. The Si(4)-O(9) bond length is 1.62 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one La(1), one La(2), one La(4), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one La(2), one La(3), one La(4), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one La(3), one La(4), and one Si(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one La(4), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one La(4), two equivalent La(3), and one Si(2) atom to form distorted edge-sharing OLa3Si tetrahedra. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one La(1), one La(3), one La(4), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one La(1), one La(3), and one Si(2) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one La(2), two equivalent La(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one La(1), one La(2), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one La(2), one La(3), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a 1-coordinate geometry to one La(1), one La(2), one La(3), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a distorted bent 120 degrees geometry to one La(2), one Si(3), and one Si(4) atom. In the thirteenth O site, O(13) is bonded in a distorted bent 150 degrees geometry to one La(1) and one Si(3) atom. In the fourteenth O site, O(14) is bonded in a 1-coordinate geometry to one La(1), one La(2), one La(4), and one Si(3) atom.