Ca2As3 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2/c space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one As(1), one As(3), one As(5), two equivalent As(6), and three equivalent As(2) atoms. In the second Ca site, Ca(2) is bonded to one As(1), one As(2), one As(3), two equivalent As(4), and three equivalent As(5) atoms to form a mixture of distorted face, corner, and edge-sharing CaAs8 hexagonal bipyramids. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one As(2), one As(3), one As(5), two equivalent As(1), two equivalent As(4), and two equivalent As(6) atoms. In the fourth Ca site, Ca(4) is bonded in a 8-coordinate geometry to two equivalent As(2), two equivalent As(4), and four equivalent As(1) atoms. In the fifth Ca site, Ca(5) is bonded in a 8-coordinate geometry to two equivalent As(4), two equivalent As(5), two equivalent As(6), and four equivalent As(3) atoms. There are six inequivalent As sites. In the first As site, As(5) is bonded in a 7-coordinate geometry to one Ca(1), one Ca(3), one Ca(5), three equivalent Ca(2), and one As(4) atom. In the second As site, As(6) is bonded in a 7-coordinate geometry to one Ca(5), two equivalent Ca(1), two equivalent Ca(3), one As(3), and one As(4) atom. In the third As site, As(1) is bonded in a 8-coordinate geometry to one Ca(1), one Ca(2), two equivalent Ca(3), two equivalent Ca(4), one As(1), and one As(2) atom. In the fourth As site, As(2) is bonded in a 7-coordinate geometry to one Ca(2), one Ca(3), one Ca(4), three equivalent Ca(1), and one As(1) atom. In the fifth As site, As(3) is bonded in a 7-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), two equivalent Ca(5), one As(3), and one As(6) atom. In the sixth As site, As(4) is bonded in a 8-coordinate geometry to one Ca(4), one Ca(5), two equivalent Ca(2), two equivalent Ca(3), one As(5), and one As(6) atom.
Ca2As3 is Magnesium tetraboride-like structured and crystallizes in the monoclinic P2/c space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to one As(1), one As(3), one As(5), two equivalent As(6), and three equivalent As(2) atoms. The Ca(1)-As(1) bond length is 3.05 Å. The Ca(1)-As(3) bond length is 3.26 Å. The Ca(1)-As(5) bond length is 3.36 Å. There is one shorter (3.07 Å) and one longer (3.11 Å) Ca(1)-As(6) bond length. There are a spread of Ca(1)-As(2) bond distances ranging from 3.04-3.35 Å. In the second Ca site, Ca(2) is bonded to one As(1), one As(2), one As(3), two equivalent As(4), and three equivalent As(5) atoms to form a mixture of distorted face, corner, and edge-sharing CaAs8 hexagonal bipyramids. The Ca(2)-As(1) bond length is 3.13 Å. The Ca(2)-As(2) bond length is 3.09 Å. The Ca(2)-As(3) bond length is 3.04 Å. There is one shorter (3.03 Å) and one longer (3.41 Å) Ca(2)-As(4) bond length. There are a spread of Ca(2)-As(5) bond distances ranging from 2.98-3.16 Å. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one As(2), one As(3), one As(5), two equivalent As(1), two equivalent As(4), and two equivalent As(6) atoms. The Ca(3)-As(2) bond length is 3.01 Å. The Ca(3)-As(3) bond length is 3.06 Å. The Ca(3)-As(5) bond length is 3.02 Å. There is one shorter (3.04 Å) and one longer (3.36 Å) Ca(3)-As(1) bond length. There is one shorter (3.09 Å) and one longer (3.11 Å) Ca(3)-As(4) bond length. There is one shorter (3.02 Å) and one longer (3.57 Å) Ca(3)-As(6) bond length. In the fourth Ca site, Ca(4) is bonded in a 8-coordinate geometry to two equivalent As(2), two equivalent As(4), and four equivalent As(1) atoms. Both Ca(4)-As(2) bond lengths are 3.06 Å. Both Ca(4)-As(4) bond lengths are 3.07 Å. There are two shorter (3.14 Å) and two longer (3.22 Å) Ca(4)-As(1) bond lengths. In the fifth Ca site, Ca(5) is bonded in a 8-coordinate geometry to two equivalent As(4), two equivalent As(5), two equivalent As(6), and four equivalent As(3) atoms. Both Ca(5)-As(4) bond lengths are 3.45 Å. Both Ca(5)-As(5) bond lengths are 3.02 Å. Both Ca(5)-As(6) bond lengths are 2.93 Å. There are two shorter (3.12 Å) and two longer (3.22 Å) Ca(5)-As(3) bond lengths. There are six inequivalent As sites. In the first As site, As(5) is bonded in a 7-coordinate geometry to one Ca(1), one Ca(3), one Ca(5), three equivalent Ca(2), and one As(4) atom. The As(5)-As(4) bond length is 2.50 Å. In the second As site, As(6) is bonded in a 7-coordinate geometry to one Ca(5), two equivalent Ca(1), two equivalent Ca(3), one As(3), and one As(4) atom. The As(6)-As(3) bond length is 2.59 Å. The As(6)-As(4) bond length is 2.51 Å. In the third As site, As(1) is bonded in a 8-coordinate geometry to one Ca(1), one Ca(2), two equivalent Ca(3), two equivalent Ca(4), one As(1), and one As(2) atom. The As(1)-As(1) bond length is 2.54 Å. The As(1)-As(2) bond length is 2.49 Å. In the fourth As site, As(2) is bonded in a 7-coordinate geometry to one Ca(2), one Ca(3), one Ca(4), three equivalent Ca(1), and one As(1) atom. In the fifth As site, As(3) is bonded in a 7-coordinate geometry to one Ca(1), one Ca(2), one Ca(3), two equivalent Ca(5), one As(3), and one As(6) atom. The As(3)-As(3) bond length is 2.47 Å. In the sixth As site, As(4) is bonded in a 8-coordinate geometry to one Ca(4), one Ca(5), two equivalent Ca(2), two equivalent Ca(3), one As(5), and one As(6) atom.