MD-MEAM investigation into surface vs bulk structure when cooling the model fcc 5f-metal

摘要

It was shown in that a δ-like reconstruction forms on α-Pu surface at ambient temperature and above. Hence, the question arises: Whether the reconstruction is proper to Pu itself or it is caused by impurities somehow accumulated at the surface of the monoclinic phase? In the paper we presented classical molecular dynamics (MD) with Modified Embedded Atom Model (MEAM) simulations to investigate the role of primary radiation defects and radiogenic helium as factors affecting the phase stability of a model fcc 5f-alloys in cooling-heating cycles at ambient pressure. The model fcc 5f-alloys equilibrated at ambient conditions were subjected to cooling-heating cycles in which they were initially cooled down to 100K and then heated up to 500K at ambient pressure. The simulations showed that the initial fcc phase undergoes polymorphous transition at cooling to a lower symmetry rhombohedral phase which is in some sense similar to alpha' phase registered in experiments. Upon heating the reconstruction of the fcc structure takes place. Thus, it was shown that the MD-MEAM technique can be applied to the investigations into peculiarities of fcc alloy phase stability.