CALCULATED LATTICE-RELAXATION IN PU-GA ALLOYS

Hellman-Feynman forces on atoms in Pu-32 and Pu31Ga supercells are cal culated with the full-potential LMTO method in the local density appro ximation. These forces are minimized by adjusting atomic positions usi ng an iterative Broyden scheme. A Pu-32 supercell shows no tendency to relax from a perfect fee lattice. In Pu31Ga the nearest-neighbor shel l of plutonium atoms relaxes inward by 1.04% of the initial theoretica l bond length (2.86 Angstrom) compared with a measured (EXAFS) value o f 3.7% for an alloy with similar composition. Possible sources of the discrepancy between theory and experiment are discussed. (C) 1998 Else vier Science S.A.