High-precision molecular dynamics simulation of UO2–PuO2: Pair potentials comparison in UO2

Our series of articles is devoted to high-precision molecular dynamics simulation of mixed actinide-oxide (MOX) fuel in the approximation of rigid ions and pair interactions (RIPI) using high-performance graphics processors (GPU). In this first article ten most recent and widely used interatomic sets of pair potentials (SPP) are assessed by reproduction of solid phase properties of uranium dioxide (UO2) – temperature dependences of the lattice constant, bulk modulus, enthalpy and heat capacity. Measurements were performed with 1 K accuracy in a wide temperature range from 300 K up to melting points. The best results are demonstrated by two recent SPPs MOX-07 and Yakub-09, which both had been fitted to the recommended thermal expansion in the range of temperatures 300–3100 K. They reproduce the experimental data better than the widely used SPPs Basak-03 and Morelon-03 at temperatures above 2500 K.

► We perform MD simulation of solid UO2 with ten sets of rigid ions pair potentials.
► In wide range of sizes (96–12000 ions) and temperatures (300–7100 K with 1 K accuracy).
► For each of ten sets λ-peak of isochoric heat capacity is unambiguously revealed.
► λ-Peaks have finite height and wide breadth unlike “delta-functions” assumed before.
► Best results are shown by two sets fitted to thermal expansion across 300–3100 K.