Na3AlH6 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent H(1), two equivalent H(2), and two equivalent H(3) atoms to form NaH6 octahedra that share corners with six equivalent Al(1)H6 octahedra. The corner-sharing octahedral tilt angles range from 30-37°. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to two equivalent H(1), two equivalent H(3), and three equivalent H(2) atoms. Al(1) is bonded to two equivalent H(1), two equivalent H(2), and two equivalent H(3) atoms to form AlH6 octahedra that share corners with six equivalent Na(1)H6 octahedra. The corner-sharing octahedral tilt angles range from 30-37°. There are three inequivalent H sites. In the first H site, H(1) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one Al(1) atom. In the second H site, H(2) is bonded in a 3-coordinate geometry to one Na(1), three equivalent Na(2), and one Al(1) atom. In the third H site, H(3) is bonded to one Na(1), two equivalent Na(2), and one Al(1) atom to form distorted corner-sharing HNa3Al tetrahedra.
Na3AlH6 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent H(1), two equivalent H(2), and two equivalent H(3) atoms to form NaH6 octahedra that share corners with six equivalent Al(1)H6 octahedra. The corner-sharing octahedral tilt angles range from 30-37°. Both Na(1)-H(1) bond lengths are 2.25 Å. Both Na(1)-H(2) bond lengths are 2.20 Å. Both Na(1)-H(3) bond lengths are 2.24 Å. In the second Na site, Na(2) is bonded in a 7-coordinate geometry to two equivalent H(1), two equivalent H(3), and three equivalent H(2) atoms. There is one shorter (2.26 Å) and one longer (2.53 Å) Na(2)-H(1) bond length. There is one shorter (2.25 Å) and one longer (2.32 Å) Na(2)-H(3) bond length. There are a spread of Na(2)-H(2) bond distances ranging from 2.26-2.63 Å. Al(1) is bonded to two equivalent H(1), two equivalent H(2), and two equivalent H(3) atoms to form AlH6 octahedra that share corners with six equivalent Na(1)H6 octahedra. The corner-sharing octahedral tilt angles range from 30-37°. Both Al(1)-H(1) bond lengths are 1.76 Å. Both Al(1)-H(2) bond lengths are 1.75 Å. Both Al(1)-H(3) bond lengths are 1.75 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Na(2), and one Al(1) atom. In the second H site, H(2) is bonded in a 3-coordinate geometry to one Na(1), three equivalent Na(2), and one Al(1) atom. In the third H site, H(3) is bonded to one Na(1), two equivalent Na(2), and one Al(1) atom to form distorted corner-sharing HNa3Al tetrahedra.