title: Statistical Nature of Atomic Disorder in Irradiated Crystals.
abstract: Atomic disorder in irradiated materials is investigated by means of x-ray diffraction, using cubic SiC single crystals as a model material. It is shown that, besides the determination of depth-resolved strain and damage profiles, x-ray diffraction can be efficiently used to determine the probability density function (PDF) of the atomic displacements within the crystal. This task is achieved by analyzing the diffraction-order dependence of the damage profiles. We thereby demonstrate that atomic displacements undergo Lévy flights, with a displacement PDF exhibiting heavy tails [with a tail index in the γ=0.73-0.37 range, i.e., far from the commonly assumed Gaussian case (γ=2)]. It is further demonstrated that these heavy tails are crucial to account for the amorphization kinetics in SiC. From the retrieved displacement PDFs we introduce a dimensionless parameter f_{D}^{XRD} to quantify the disordering. f_{D}^{XRD} is found to be consistent with both independent measurements using ion channeling and with molecular dynamics calculations.
authors.affiliation: Science des Procédés Céramiques et Traitements de Surface, CNRS UMR 7315, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges, France.
authors.forename: A
authors.initials: A
authors.lastname: Boulle
authors.affiliation: Centre de Sciences Nucléaires et de Sciences de la Matière, Université Paris-Sud, CNRS/IN2P3, Université Paris Saclay 91405 Orsay, France.
authors.forename: A
authors.initials: A
authors.lastname: Debelle