Atomic scale simulations provide insights on swelling induced by irradiations

Abstract

International audienceRationale of the responses of materials to irradiation is commonly based on separate post-mortem analysis of experiments and primary damage states obtained by atomistic simulations of displacement cascades.We developed in recent years an atomic scale methodology that gives access to irradiation doses for materials in which displacements cascades boil down to point defects only. Irradiation dose is obtained by accumulation of these point defects mimicking time-consuming cascades overlap. Such methodology proved to be very efficient in providing atomic scale explanations of irradiation effects in term of swelling for different materials such as graphite or urania.We show for example in irradiated graphite [1] that the well-known anisotropic volume change characterized by a shrinking in basal plane and a swelling in the c-axis is not related only to the widening of graphene interlayer caused by interstitials. It relies also to wrinkling of graphene layers with same physical laws as for rippling of carpets or curtains. In irradiated urania [2], we also bring an atomic scale explanation to the well-known dilatation-contraction peak observed in the early stage of irradiations. It is related to the transformation of Frank loops which significantly contribute to the swelling into perfect dislocations which release strain