La2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), two equivalent O(6), and two equivalent O(7) atoms. In the second La site, La(2) is bonded in a 8-coordinate geometry to one O(1), one O(4), one O(6), one O(7), two equivalent O(2), and two equivalent O(3) atoms. There are two 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(5) 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. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(6) is bonded in a 4-coordinate geometry to one La(2), two equivalent La(1), and one Si(2) atom. In the third O site, O(7) is bonded in a 4-coordinate geometry to one La(2), two equivalent La(1), and one Si(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one La(1), two equivalent La(2), and one Si(1) atom. In the sixth O site, O(3) is bonded in a 4-coordinate geometry to one La(1), two equivalent La(2), and one Si(1) atom. In the seventh O site, O(4) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(2) atom.
La2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), two equivalent O(6), and two equivalent O(7) atoms. The La(1)-O(1) bond length is 2.30 Å. The La(1)-O(2) bond length is 2.60 Å. The La(1)-O(3) bond length is 2.60 Å. The La(1)-O(4) bond length is 2.53 Å. There is one shorter (2.48 Å) and one longer (2.69 Å) La(1)-O(6) bond length. There is one shorter (2.57 Å) and one longer (2.62 Å) La(1)-O(7) bond length. In the second La site, La(2) is bonded in a 8-coordinate geometry to one O(1), one O(4), one O(6), one O(7), two equivalent O(2), and two equivalent O(3) atoms. The La(2)-O(1) bond length is 2.53 Å. The La(2)-O(4) bond length is 2.43 Å. The La(2)-O(6) bond length is 2.74 Å. The La(2)-O(7) bond length is 2.49 Å. There is one shorter (2.42 Å) and one longer (2.80 Å) La(2)-O(2) bond length. There is one shorter (2.47 Å) and one longer (2.86 Å) La(2)-O(3) bond length. There are two 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(5) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.61 Å. The Si(1)-O(2) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.63 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 1.61 Å. The Si(2)-O(5) bond length is 1.62 Å. The Si(2)-O(6) bond length is 1.63 Å. The Si(2)-O(7) bond length is 1.65 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(6) is bonded in a 4-coordinate geometry to one La(2), two equivalent La(1), and one Si(2) atom. In the third O site, O(7) is bonded in a 4-coordinate geometry to one La(2), two equivalent La(1), and one Si(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one La(1), two equivalent La(2), and one Si(1) atom. In the sixth O site, O(3) is bonded in a 4-coordinate geometry to one La(1), two equivalent La(2), and one Si(1) atom. In the seventh O site, O(4) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(2) atom.