LaAs2 crystallizes in the monoclinic Cc space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(5), one As(7), one As(8), two equivalent As(3), and two equivalent As(6) atoms. In the second La site, La(2) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(3), one As(5), one As(8), two equivalent As(4), and two equivalent As(7) atoms. In the third La site, La(3) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(5), one As(6), one As(8), two equivalent As(3), and two equivalent As(4) atoms. In the fourth La site, La(4) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(4), one As(5), one As(8), two equivalent As(6), and two equivalent As(7) atoms. There are eight inequivalent As sites. In the first As site, As(1) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(2), and one As(5) atom. In the second As site, As(2) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(1), and one As(4) atom. In the third As site, As(3) is bonded in a 6-coordinate geometry to one La(2), two equivalent La(1), two equivalent La(3), and one As(5) atom. In the fourth As site, As(4) is bonded in a 6-coordinate geometry to one La(4), two equivalent La(2), two equivalent La(3), and one As(2) atom. In the fifth As site, As(5) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(1), and one As(3) atom. In the sixth As site, As(6) is bonded to one La(3), two equivalent La(1), two equivalent La(4), and one As(8) atom to form a mixture of distorted corner, edge, and face-sharing AsLa5As octahedra. The corner-sharing octahedral tilt angles range from 38-51°. In the seventh As site, As(7) is bonded to one La(1), two equivalent La(2), two equivalent La(4), and one As(8) atom to form a mixture of distorted corner, edge, and face-sharing AsLa5As octahedra. The corner-sharing octahedral tilt angles range from 39-47°. In the eighth As site, As(8) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(6), and one As(7) atom.
LaAs2 crystallizes in the monoclinic Cc space group. There are four inequivalent La sites. In the first La site, La(1) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(5), one As(7), one As(8), two equivalent As(3), and two equivalent As(6) atoms. The La(1)-As(1) bond length is 3.22 Å. The La(1)-As(2) bond length is 3.29 Å. The La(1)-As(5) bond length is 3.35 Å. The La(1)-As(7) bond length is 3.14 Å. The La(1)-As(8) bond length is 3.24 Å. There is one shorter (3.17 Å) and one longer (3.21 Å) La(1)-As(3) bond length. There is one shorter (3.07 Å) and one longer (3.18 Å) La(1)-As(6) bond length. In the second La site, La(2) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(3), one As(5), one As(8), two equivalent As(4), and two equivalent As(7) atoms. The La(2)-As(1) bond length is 3.20 Å. The La(2)-As(2) bond length is 3.07 Å. The La(2)-As(3) bond length is 3.09 Å. The La(2)-As(5) bond length is 3.24 Å. The La(2)-As(8) bond length is 3.18 Å. There is one shorter (3.13 Å) and one longer (3.26 Å) La(2)-As(4) bond length. There is one shorter (3.12 Å) and one longer (3.17 Å) La(2)-As(7) bond length. In the third La site, La(3) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(5), one As(6), one As(8), two equivalent As(3), and two equivalent As(4) atoms. The La(3)-As(1) bond length is 3.11 Å. The La(3)-As(2) bond length is 3.14 Å. The La(3)-As(5) bond length is 3.14 Å. The La(3)-As(6) bond length is 3.10 Å. The La(3)-As(8) bond length is 3.29 Å. There is one shorter (3.13 Å) and one longer (3.18 Å) La(3)-As(3) bond length. There is one shorter (3.10 Å) and one longer (3.22 Å) La(3)-As(4) bond length. In the fourth La site, La(4) is bonded in a 9-coordinate geometry to one As(1), one As(2), one As(4), one As(5), one As(8), two equivalent As(6), and two equivalent As(7) atoms. The La(4)-As(1) bond length is 3.21 Å. The La(4)-As(2) bond length is 3.34 Å. The La(4)-As(4) bond length is 3.15 Å. The La(4)-As(5) bond length is 3.20 Å. The La(4)-As(8) bond length is 3.06 Å. There is one shorter (3.19 Å) and one longer (3.25 Å) La(4)-As(6) bond length. There is one shorter (3.16 Å) and one longer (3.20 Å) La(4)-As(7) bond length. There are eight inequivalent As sites. In the first As site, As(1) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(2), and one As(5) atom. The As(1)-As(2) bond length is 2.56 Å. The As(1)-As(5) bond length is 2.50 Å. In the second As site, As(2) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(1), and one As(4) atom. The As(2)-As(4) bond length is 2.45 Å. In the third As site, As(3) is bonded in a 6-coordinate geometry to one La(2), two equivalent La(1), two equivalent La(3), and one As(5) atom. The As(3)-As(5) bond length is 2.46 Å. In the fourth As site, As(4) is bonded in a 6-coordinate geometry to one La(4), two equivalent La(2), two equivalent La(3), and one As(2) atom. In the fifth As site, As(5) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(1), and one As(3) atom. In the sixth As site, As(6) is bonded to one La(3), two equivalent La(1), two equivalent La(4), and one As(8) atom to form a mixture of distorted corner, edge, and face-sharing AsLa5As octahedra. The corner-sharing octahedral tilt angles range from 38-51°. The As(6)-As(8) bond length is 2.46 Å. In the seventh As site, As(7) is bonded to one La(1), two equivalent La(2), two equivalent La(4), and one As(8) atom to form a mixture of distorted corner, edge, and face-sharing AsLa5As octahedra. The corner-sharing octahedral tilt angles range from 39-47°. The As(7)-As(8) bond length is 2.50 Å. In the eighth As site, As(8) is bonded in a 6-coordinate geometry to one La(1), one La(2), one La(3), one La(4), one As(6), and one As(7) atom.