When compressed at room temperature to 5 GPa, α-Am transforms to the β modification, which has a face-centered cubic (fcc) symmetry, space group Fmm and lattice constant a = 489 pm. This fcc structure is equivalent to the closest packing with the sequence ABC. Upon further compression to 23 GPa, americium transforms to an orthorhombic γ-Am structure similar to that of α-uranium.
At room temperature and under pressure of 5 GPa, α-Am undergoes a transformation into the β modification with face-centered cubic (fcc) symmetry, space group Fmm, and a lattice constant of 489 pm. This fcc structure is equivalent to the most efficient packing arrangement with the sequence ABC. Further compression to 23 GPa leads to the formation of an orthorhombic γ-Am structure similar to α-uranium.