Theoretical Atomic Volumes of fcc Thorium and Plutonium

The zero-presssure zero-temperature equilibrium volume and bulk modulus are calculated for fcc Th and Pu by two independent all-electron, full-potential, electronic-structure methods: the full-potential linear augmented-plane-wave (FLAPW) method and the linear combinations of Gaussian type orbitals-fitting function (LCGTO-FF) method. The results produced by these two distinctly different electronic-structure techniques are in excellent agreement with each other, but differ significantly from a previous calculation using the full-potential linear muffin-tin-orbital (FP-LMTO) method. The theoretically calculated equilibrium volumes are nearly 10% larger than the previous FP-LMTO calculations. While the new theoretical volume for Th is in good agreement with experiment when the generalized gradient approximation is used, the calculated equilibrium volume for fcc Pu remains substantially smaller than experiment in qualitative agreement with previous calculations.