  We introduce a temperature-dependent parameterization in the modified
embedded-atom method and combine it with molecular dynamics to simulate the
diverse physical properties of the \delta - and \epsilon - phases of elemental
plutonium. The aim of this temperature-dependent parameterization is to mimic
the different magnitudes of correlation strength of the Pu 5f electrons at
different temperatures. Compared to previous temperature independent
parameterization, our approach captures the negative thermal expansion and
temperature dependence of the bulk moduli in the \delta -phase. We trace this
improvement to a strong softening of phonons near the zone boundary and an
increase of the f-like partial density and anharmonic effects induced by the
temperature-dependent parameterization upon increasing temperature. Our study
suggests it is important to include temperature-dependent parameterization in
classical force field methods to simulate complex materials such as Pu.
