La4H9 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a distorted body-centered cubic geometry to one H(2) and eight equivalent H(1) atoms. In the second La site, La(2) is bonded in a distorted body-centered cubic geometry to two equivalent H(2) and eight equivalent H(1) atoms. There are two inequivalent H sites. In the first H site, H(1) is bonded to two equivalent La(1) and two equivalent La(2) atoms to form HLa4 tetrahedra that share corners with three equivalent H(2)La6 octahedra, corners with sixteen equivalent H(1)La4 tetrahedra, edges with six equivalent H(1)La4 tetrahedra, and  a faceface with one H(2)La6 octahedra. The corner-sharing octahedral tilt angles range from 53-56°. In the second H site, H(2) is bonded to two equivalent La(1) and four equivalent La(2) atoms to form HLa6 octahedra that share corners with four equivalent H(2)La6 octahedra, corners with twenty-four equivalent H(1)La4 tetrahedra, and faces with eight equivalent H(1)La4 tetrahedra. The corner-sharing octahedra are not tilted.
La4H9 crystallizes in the tetragonal I4/mmm space group. There are two inequivalent La sites. In the first La site, La(1) is bonded in a distorted body-centered cubic geometry to one H(2) and eight equivalent H(1) atoms. The La(1)-H(2) bond length is 2.79 Å. There are four shorter (2.40 Å) and four longer (2.46 Å) La(1)-H(1) bond lengths. In the second La site, La(2) is bonded in a distorted body-centered cubic geometry to two equivalent H(2) and eight equivalent H(1) atoms. Both La(2)-H(2) bond lengths are 2.81 Å. All La(2)-H(1) bond lengths are 2.45 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded to two equivalent La(1) and two equivalent La(2) atoms to form HLa4 tetrahedra that share corners with three equivalent H(2)La6 octahedra, corners with sixteen equivalent H(1)La4 tetrahedra, edges with six equivalent H(1)La4 tetrahedra, and  a faceface with one H(2)La6 octahedra. The corner-sharing octahedral tilt angles range from 53-56°. In the second H site, H(2) is bonded to two equivalent La(1) and four equivalent La(2) atoms to form HLa6 octahedra that share corners with four equivalent H(2)La6 octahedra, corners with twenty-four equivalent H(1)La4 tetrahedra, and faces with eight equivalent H(1)La4 tetrahedra. The corner-sharing octahedra are not tilted.