Thermal conductivities of americium dioxide and sesquioxide by molecular dynamics simulations

Equilibrium and non-equilibrium molecular dynamics (EMD and NEMD) simulations were performed to investigate the thermal conductivities of americium dioxide and sesquioxide up to 2000 K using the Born-Mayer-Huggins interatomic potential with the partially ionic model. The potential parameters were determined based on the literature data, i.e. thermal expansion and bulk modulus. EMD and NEMD calculations gave the almost comparable results for the thermal conductivities of americium dioxide and sesquioxide at higher temperatures. The MD thermal conductivity of americium dioxide was almost comparable with the empirical value of UO2 above ca. 700 K and decreased with an increase of temperature, which resulted from Umklapp process in the phonon conduction. For contrast, MD calculations showed that the thermal conductivity of americium sesquioxide was quite low and almost independent on temperature compared to that of its dioxide. This might be the reason that the large vacant spaces, which are like oxygen vacancies, existing in americium sesquioxide played a role of the phonon-scattering.