Ba2AlH7 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to one H(3), one H(4), one H(5), one H(7), two equivalent H(1), two equivalent H(2), and three equivalent H(6) atoms. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to one H(1), one H(2), one H(4), two equivalent H(3), two equivalent H(5), and three equivalent H(7) atoms. Al(1) is bonded in an octahedral geometry to one H(1), one H(2), one H(3), one H(4), one H(5), and one H(6) atom. There are seven inequivalent H sites. In the first H site, H(3) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Al(1) atom. In the second H site, H(4) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one Al(1) atom. In the third H site, H(5) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Al(1) atom. In the fourth H site, H(6) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one Al(1) atom. In the fifth H site, H(7) is bonded to one Ba(1) and three equivalent Ba(2) atoms to form a mixture of edge and corner-sharing HBa4 tetrahedra. In the sixth H site, H(1) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one Al(1) atom. In the seventh H site, H(2) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one Al(1) atom.
Ba2AlH7 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 11-coordinate geometry to one H(3), one H(4), one H(5), one H(7), two equivalent H(1), two equivalent H(2), and three equivalent H(6) atoms. The Ba(1)-H(3) bond length is 2.72 Å. The Ba(1)-H(4) bond length is 2.80 Å. The Ba(1)-H(5) bond length is 2.65 Å. The Ba(1)-H(7) bond length is 2.68 Å. There is one shorter (2.69 Å) and one longer (2.87 Å) Ba(1)-H(1) bond length. There is one shorter (2.84 Å) and one longer (2.92 Å) Ba(1)-H(2) bond length. There are two shorter (2.77 Å) and one longer (2.83 Å) Ba(1)-H(6) bond length. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to one H(1), one H(2), one H(4), two equivalent H(3), two equivalent H(5), and three equivalent H(7) atoms. The Ba(2)-H(1) bond length is 2.67 Å. The Ba(2)-H(2) bond length is 2.82 Å. The Ba(2)-H(4) bond length is 2.86 Å. There is one shorter (2.59 Å) and one longer (2.82 Å) Ba(2)-H(3) bond length. There is one shorter (2.66 Å) and one longer (2.80 Å) Ba(2)-H(5) bond length. There are a spread of Ba(2)-H(7) bond distances ranging from 2.64-2.78 Å. Al(1) is bonded in an octahedral geometry to one H(1), one H(2), one H(3), one H(4), one H(5), and one H(6) atom. The Al(1)-H(1) bond length is 1.73 Å. The Al(1)-H(2) bond length is 1.79 Å. The Al(1)-H(3) bond length is 1.73 Å. The Al(1)-H(4) bond length is 1.75 Å. The Al(1)-H(5) bond length is 1.74 Å. The Al(1)-H(6) bond length is 1.73 Å. There are seven inequivalent H sites. In the first H site, H(3) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Al(1) atom. In the second H site, H(4) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), and one Al(1) atom. In the third H site, H(5) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Al(1) atom. In the fourth H site, H(6) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one Al(1) atom. In the fifth H site, H(7) is bonded to one Ba(1) and three equivalent Ba(2) atoms to form a mixture of edge and corner-sharing HBa4 tetrahedra. In the sixth H site, H(1) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one Al(1) atom. In the seventh H site, H(2) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one Al(1) atom.