La4Si4I3 crystallizes in the monoclinic C2/m space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 10-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(4), four equivalent Si(3), and one I(3) atom. In the second La site, La(2) is bonded in a 9-coordinate geometry to two equivalent Si(2), four equivalent Si(1), one I(2), and two equivalent I(3) atoms. In the third La site, La(3) is bonded in a 8-coordinate geometry to two equivalent Si(3), two equivalent Si(4), one I(3), and three equivalent I(1) atoms. In the fourth La site, La(4) is bonded to one Si(1), two equivalent Si(2), two equivalent Si(4), one I(1), and two equivalent I(2) atoms to form distorted face-sharing LaSi5I3 hexagonal bipyramids. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one La(1), one La(4), four equivalent La(2), one Si(1), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent La(1), two equivalent La(2), two equivalent La(4), one Si(4), and two equivalent Si(1) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent La(3), four equivalent La(1), one Si(3), and one Si(4) atom. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent La(1), two equivalent La(3), two equivalent La(4), one Si(2), and one Si(3) atom. There are three inequivalent I sites. In the first I site, I(1) is bonded to one La(4) and three equivalent La(3) atoms to form a mixture of distorted corner and edge-sharing ILa4 tetrahedra. In the second I site, I(2) is bonded in a distorted T-shaped geometry to one La(2) and two equivalent La(4) atoms. In the third I site, I(3) is bonded to one La(1), one La(3), and two equivalent La(2) atoms to form distorted corner-sharing ILa4 trigonal pyramids.
La4Si4I3 crystallizes in the monoclinic C2/m space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 10-coordinate geometry to one Si(1), two equivalent Si(2), two equivalent Si(4), four equivalent Si(3), and one I(3) atom. The La(1)-Si(1) bond length is 3.25 Å. Both La(1)-Si(2) bond lengths are 3.19 Å. Both La(1)-Si(4) bond lengths are 3.23 Å. There are two shorter (3.18 Å) and two longer (3.27 Å) La(1)-Si(3) bond lengths. The La(1)-I(3) bond length is 3.34 Å. In the second La site, La(2) is bonded in a 9-coordinate geometry to two equivalent Si(2), four equivalent Si(1), one I(2), and two equivalent I(3) atoms. There is one shorter (3.10 Å) and one longer (3.19 Å) La(2)-Si(2) bond length. There are two shorter (3.17 Å) and two longer (3.20 Å) La(2)-Si(1) bond lengths. The La(2)-I(2) bond length is 3.30 Å. Both La(2)-I(3) bond lengths are 3.35 Å. In the third La site, La(3) is bonded in a 8-coordinate geometry to two equivalent Si(3), two equivalent Si(4), one I(3), and three equivalent I(1) atoms. Both La(3)-Si(3) bond lengths are 3.12 Å. Both La(3)-Si(4) bond lengths are 3.10 Å. The La(3)-I(3) bond length is 3.43 Å. There are two shorter (3.40 Å) and one longer (3.63 Å) La(3)-I(1) bond length. In the fourth La site, La(4) is bonded to one Si(1), two equivalent Si(2), two equivalent Si(4), one I(1), and two equivalent I(2) atoms to form distorted face-sharing LaSi5I3 hexagonal bipyramids. The La(4)-Si(1) bond length is 3.01 Å. Both La(4)-Si(2) bond lengths are 3.16 Å. Both La(4)-Si(4) bond lengths are 3.13 Å. The La(4)-I(1) bond length is 3.33 Å. Both La(4)-I(2) bond lengths are 3.25 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one La(1), one La(4), four equivalent La(2), one Si(1), and two equivalent Si(2) atoms. The Si(1)-Si(1) bond length is 2.43 Å. Both Si(1)-Si(2) bond lengths are 2.45 Å. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to two equivalent La(1), two equivalent La(2), two equivalent La(4), one Si(4), and two equivalent Si(1) atoms. The Si(2)-Si(4) bond length is 2.43 Å. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to two equivalent La(3), four equivalent La(1), one Si(3), and one Si(4) atom. The Si(3)-Si(3) bond length is 2.48 Å. The Si(3)-Si(4) bond length is 2.38 Å. In the fourth Si site, Si(4) is bonded in a 8-coordinate geometry to two equivalent La(1), two equivalent La(3), two equivalent La(4), one Si(2), and one Si(3) atom. There are three inequivalent I sites. In the first I site, I(1) is bonded to one La(4) and three equivalent La(3) atoms to form a mixture of distorted corner and edge-sharing ILa4 tetrahedra. In the second I site, I(2) is bonded in a distorted T-shaped geometry to one La(2) and two equivalent La(4) atoms. In the third I site, I(3) is bonded to one La(1), one La(3), and two equivalent La(2) atoms to form distorted corner-sharing ILa4 trigonal pyramids.