The crystal structure of 241Am has been investigated up to 18.0 GPa, using a diamond anvil high-pressure apparatus. The normal dhep form of Am, stable at 1 atm and room temperature, undergoes three-phase transformations below 18.0 GPa. The first transformation occurs at about 5.0¿1.0 GPa, the second occurs at about 10.0¿1.0 GPa, and the third occurs at about 15.0¿1.0 GPa. The structure of the Am phase at 5-GPa pressure is fcc. However, we are unable to determine the structure of the new phases at about 10.0- and 15.0-GPa pressure from our present data. The structural behavior of Am showing that Am undergoes a sequence of structural transformations somewhat similar to the lanthanide metals is discussed. |