Effective Hamiltonian for metallic Pu

We derive a low-energy effective Hamiltonian H ˜ Pu for metallic Pu by assuming that intra-atomic Coulomb and spin–orbit interactions are much stronger than the kinetic energy terms. An important property of H ˜ Pu is the exact cancellation of the effective f - f hopping tensor that places Pu closer to lanthanide systems such as Ce or mixed valent Sm than to the rest of the actinides. The similarity between the low-energy models of Pu and these mixed valent lanthanide systems could be the common root for explaining the large volume expansions observed in all of them.