Atomic-scale modeling of 12〈110〉{001} edge dislocations in UO2: Core properties and mobility

The dislocation properties of UO2, the main nuclear fuel material, are important ingredients to model the mechanical properties and predict nominal and accidental operations of nuclear plant reactors. However, the plastic behaviour of UO2 is complex with little known about dislocations and other extended defects. In this study, we use a combination of interatomic potential-based atomistic simulations and ab initio calculations to investigate the core structure and mobility of the 12〈110〉{001} edge dislocation, which controls the plasticity of UO2 single crystals. Various dislocation cores are obtained and compared, including the classical asymmetric Ashbee core and a so-far unreported core made of an alternation of both variants of the Ashbee core along the dislocation line. This new core, called here zigzag, is ubiquitous in molecular dynamics simulations at high temperature in the nominal-to-accidental transient regime (1600 to 2200 K). Molecular dynamics is also used to determine the velocity of the edge dislocation as a function of temperature and stress. A dislocation mobility law is adjusted from the simulations and provides an up-scaling ingredient central to the multi-scale modeling of UO2 nuclear fuel mechanical properties.