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AcH2 is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ac is bonded in a body-centered cubic geometry to eight equivalent H atoms. All Ac–H bond lengths are 2.56 Å. H is bonded to four equivalent Ac atoms to form a mixture of edge and corner-sharing HAc4 tetrahedra.
AcH3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ac3+ is bonded in a distorted body-centered cubic geometry to fourteen H1- atoms. There are eight shorter (2.51 Å) and six longer (2.90 Å) Ac–H bond lengths. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded to four equivalent Ac3+ atoms to form HAc4 tetrahedra that share corners with twelve equivalent HAc6 octahedra, corners with sixteen equivalent HAc4 tetrahedra, edges with six equivalent HAc4 tetrahedra, and faces with four equivalent HAc6 octahedra. The corner-sharing octahedral tilt angles are 55°. In the second H1- site, H1- is bonded to six equivalent Ac3+ atoms to form HAc6 octahedra that share corners with six equivalent HAc6 octahedra, corners with twenty-four equivalent HAc4 tetrahedra, edges with twelve equivalent HAc6 octahedra, and faces with eight equivalent HAc4 tetrahedra. The corner-sharing octahedral tilt angles are 0°.