ErH3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. Er(1) is bonded in a distorted body-centered cubic geometry to six 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 four equivalent Er(1) atoms to form HEr4 tetrahedra that share corners with twelve equivalent H(2)Er6 octahedra, corners with sixteen equivalent H(1)Er4 tetrahedra, edges with six equivalent H(1)Er4 tetrahedra, and faces with four equivalent H(2)Er6 octahedra. The corner-sharing octahedral tilt angles are 55°. In the second H site, H(2) is bonded to six equivalent Er(1) atoms to form HEr6 octahedra that share corners with six equivalent H(2)Er6 octahedra, corners with twenty-four equivalent H(1)Er4 tetrahedra, edges with twelve equivalent H(2)Er6 octahedra, and faces with eight equivalent H(1)Er4 tetrahedra. The corner-sharing octahedra are not tilted.
ErH3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. Er(1) is bonded in a distorted body-centered cubic geometry to six equivalent H(2) and eight equivalent H(1) atoms. All Er(1)-H(2) bond lengths are 2.55 Å. All Er(1)-H(1) bond lengths are 2.21 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded to four equivalent Er(1) atoms to form HEr4 tetrahedra that share corners with twelve equivalent H(2)Er6 octahedra, corners with sixteen equivalent H(1)Er4 tetrahedra, edges with six equivalent H(1)Er4 tetrahedra, and faces with four equivalent H(2)Er6 octahedra. The corner-sharing octahedral tilt angles are 55°. In the second H site, H(2) is bonded to six equivalent Er(1) atoms to form HEr6 octahedra that share corners with six equivalent H(2)Er6 octahedra, corners with twenty-four equivalent H(1)Er4 tetrahedra, edges with twelve equivalent H(2)Er6 octahedra, and faces with eight equivalent H(1)Er4 tetrahedra. The corner-sharing octahedra are not tilted.