Ho3Al2(Ni3H4)2 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 4-coordinate geometry to four equivalent H(1) atoms. In the second Ho site, Ho(2) is bonded in a 5-coordinate geometry to one H(4) and four equivalent H(1) atoms. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Al(1) and two equivalent H(2) atoms. In the second Ni site, Ni(2) is bonded in a 3-coordinate geometry to two equivalent Al(1), one H(2), one H(3), and one H(4) atom. Al(1) is bonded in a distorted linear geometry to two equivalent Ni(1), four equivalent Ni(2), and two equivalent H(1) atoms. There are four inequivalent H sites. In the first H site, H(1) is bonded to one Ho(1), two equivalent Ho(2), and one Al(1) atom to form HHo3Al tetrahedra that share corners with two equivalent H(4)Ho2Ni4 octahedra, corners with four equivalent H(1)Ho3Al tetrahedra, and edges with three equivalent H(1)Ho3Al tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the second H site, H(2) is bonded in a 4-coordinate geometry to two equivalent Ni(1) and two equivalent Ni(2) atoms. In the third H site, H(3) is bonded to four equivalent Ni(2) atoms to form edge-sharing HNi4 tetrahedra. In the fourth H site, H(4) is bonded to two equivalent Ho(2) and four equivalent Ni(2) atoms to form HHo2Ni4 octahedra that share corners with eight equivalent H(1)Ho3Al tetrahedra and edges with two equivalent H(3)Ni4 tetrahedra.
Ho3Al2(Ni3H4)2 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Ho sites. In the first Ho site, Ho(1) is bonded in a 4-coordinate geometry to four equivalent H(1) atoms. All Ho(1)-H(1) bond lengths are 2.11 Å. In the second Ho site, Ho(2) is bonded in a 5-coordinate geometry to one H(4) and four equivalent H(1) atoms. The Ho(2)-H(4) bond length is 2.10 Å. All Ho(2)-H(1) bond lengths are 2.11 Å. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Al(1) and two equivalent H(2) atoms. Both Ni(1)-Al(1) bond lengths are 2.44 Å. Both Ni(1)-H(2) bond lengths are 1.65 Å. In the second Ni site, Ni(2) is bonded in a 3-coordinate geometry to two equivalent Al(1), one H(2), one H(3), and one H(4) atom. Both Ni(2)-Al(1) bond lengths are 2.56 Å. The Ni(2)-H(2) bond length is 1.75 Å. The Ni(2)-H(3) bond length is 1.68 Å. The Ni(2)-H(4) bond length is 2.02 Å. Al(1) is bonded in a distorted linear geometry to two equivalent Ni(1), four equivalent Ni(2), and two equivalent H(1) atoms. Both Al(1)-H(1) bond lengths are 1.99 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded to one Ho(1), two equivalent Ho(2), and one Al(1) atom to form HHo3Al tetrahedra that share corners with two equivalent H(4)Ho2Ni4 octahedra, corners with four equivalent H(1)Ho3Al tetrahedra, and edges with three equivalent H(1)Ho3Al tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the second H site, H(2) is bonded in a 4-coordinate geometry to two equivalent Ni(1) and two equivalent Ni(2) atoms. In the third H site, H(3) is bonded to four equivalent Ni(2) atoms to form edge-sharing HNi4 tetrahedra. In the fourth H site, H(4) is bonded to two equivalent Ho(2) and four equivalent Ni(2) atoms to form HHo2Ni4 octahedra that share corners with eight equivalent H(1)Ho3Al tetrahedra and edges with two equivalent H(3)Ni4 tetrahedra.