La3Si2O7Cl3 crystallizes in the monoclinic P2_1 space group. There are three inequivalent La sites. In the first La site, La(1) is bonded in a 10-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one Cl(1), two equivalent Cl(2), and two equivalent Cl(3) atoms. In the second La site, La(2) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(7), one Cl(1), one Cl(3), and two equivalent Cl(2) atoms. In the third La site, La(3) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(6), one O(7), one Cl(3), and two equivalent Cl(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one La(1), one La(3), and one Si(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one La(2), one La(3), and one Si(1) atom. In the fourth O site, O(4) is bonded to one La(1), one La(2), one La(3), and one Si(2) atom to form distorted corner-sharing OLa3Si tetrahedra. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one La(1), one La(2), one La(3), and one Si(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one La(3), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded to one La(1), one La(2), one La(3), and one Si(1) atom to form distorted corner-sharing OLa3Si tetrahedra. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a see-saw-like geometry to one La(1), one La(2), and two equivalent La(3) atoms. In the second Cl site, Cl(2) is bonded in a distorted see-saw-like geometry to two equivalent La(1) and two equivalent La(2) atoms. In the third Cl site, Cl(3) is bonded in a see-saw-like geometry to one La(2), one La(3), and two equivalent La(1) atoms.
La3Si2O7Cl3 crystallizes in the monoclinic P2_1 space group. There are three inequivalent La sites. In the first La site, La(1) is bonded in a 10-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), one Cl(1), two equivalent Cl(2), and two equivalent Cl(3) atoms. The La(1)-O(1) bond length is 2.45 Å. The La(1)-O(2) bond length is 2.55 Å. The La(1)-O(4) bond length is 2.57 Å. The La(1)-O(5) bond length is 2.91 Å. The La(1)-O(7) bond length is 2.56 Å. The La(1)-Cl(1) bond length is 3.12 Å. There is one shorter (3.09 Å) and one longer (3.18 Å) La(1)-Cl(2) bond length. There is one shorter (3.02 Å) and one longer (3.26 Å) La(1)-Cl(3) bond length. In the second La site, La(2) is bonded in a 9-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(7), one Cl(1), one Cl(3), and two equivalent Cl(2) atoms. The La(2)-O(2) bond length is 2.35 Å. The La(2)-O(3) bond length is 2.64 Å. The La(2)-O(4) bond length is 2.52 Å. The La(2)-O(5) bond length is 2.50 Å. The La(2)-O(7) bond length is 2.52 Å. The La(2)-Cl(1) bond length is 3.15 Å. The La(2)-Cl(3) bond length is 3.19 Å. There is one shorter (2.88 Å) and one longer (3.36 Å) La(2)-Cl(2) bond length. In the third La site, La(3) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(4), one O(5), one O(6), one O(7), one Cl(3), and two equivalent Cl(1) atoms. The La(3)-O(1) bond length is 2.55 Å. The La(3)-O(3) bond length is 2.32 Å. The La(3)-O(4) bond length is 2.51 Å. The La(3)-O(5) bond length is 2.62 Å. The La(3)-O(6) bond length is 2.88 Å. The La(3)-O(7) bond length is 2.59 Å. The La(3)-Cl(3) bond length is 2.98 Å. There is one shorter (2.99 Å) and one longer (3.08 Å) La(3)-Cl(1) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(3), one O(5), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.64 Å. The Si(1)-O(6) bond length is 1.65 Å. The Si(1)-O(7) bond length is 1.66 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(1) bond length is 1.64 Å. The Si(2)-O(2) bond length is 1.62 Å. The Si(2)-O(4) bond length is 1.66 Å. The Si(2)-O(6) bond length is 1.66 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one La(1), one La(3), and one Si(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one La(1), one La(2), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one La(2), one La(3), and one Si(1) atom. In the fourth O site, O(4) is bonded to one La(1), one La(2), one La(3), and one Si(2) atom to form distorted corner-sharing OLa3Si tetrahedra. In the fifth O site, O(5) is bonded in a 1-coordinate geometry to one La(1), one La(2), one La(3), and one Si(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one La(3), one Si(1), and one Si(2) atom. In the seventh O site, O(7) is bonded to one La(1), one La(2), one La(3), and one Si(1) atom to form distorted corner-sharing OLa3Si tetrahedra. There are three inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a see-saw-like geometry to one La(1), one La(2), and two equivalent La(3) atoms. In the second Cl site, Cl(2) is bonded in a distorted see-saw-like geometry to two equivalent La(1) and two equivalent La(2) atoms. In the third Cl site, Cl(3) is bonded in a see-saw-like geometry to one La(2), one La(3), and two equivalent La(1) atoms.