Lattice vibrations in δ-plutonium:: Molecular dynamics calculation -: art. no. 014129

Analysis of previous experimental neutron diffraction measurements has shown that the amplitude of lattice vibrations in delta-Pu alloys increases more rapidly than linearly with temperature. Using a recently developed Modified Embedded Atom Method (MEAM) potential for the Pu-Ga system, molecular dynamics (MD) calculations show an almost linear increase of the lattice vibrations with temperature. However, these same MD calculations show that the predicted neutron diffraction peak intensities vary with temperature in a nonlinear fashion similar to experiment. By using two MEAM models of Pu, the first including both itinerant and localized f-electron behavior and the second, identical to the first, but with the itinerant f-electron behavior suppressed, this non-Debye behavior is shown to arise directly from the Pu itinerant f-electrons in the model and the resultant metastability of delta-Pu.