Polycrystalline uranium dioxide is currently the most widely used nuclear fuel worldwide. As a consequence, the knowledge of its thermodynamic and mechanical properties is of major interest as it has a direct impact on the safety and the efficiency of the reactor. Of course, extensive experimental results, theoretical modelling, and simulations at the atomic scale on UO2 are available in the literature. Nevertheless, experiments are usually performed on polycrystalline UO2 samples, whereas atomistic simulations often consider single-crystal systems, making comparisons difficult, especially at the scale of the grain boundary (GB).
To overcome this problem, in the present ongoing work we propose to study UO2 bicrystals by coupling experimental and atomic simulations. On the one hand, we fabricate bicrystals by the diffusion bonding method starting from two single-crystals. Resulting GBs are characterized using various methods and their energies determined by measuring the dihedral angles of the groove after thermal etching [1]. On the other hand, we build atomic configurations of the same GBs using GBStudio [2], and perform molecular dynamic (MD) simulations with LAMMPS [3]. We are thus able to determine GBs energies and atomic structures as well as to calculate some mechanical properties such as fracture strength under shear or elongation constraints. Eventually, experiments on bicrystals will allow strengthening the reliability of atomic simulations results.
In this presentation, we will show MD results on GBs energies and local structures obtained with several empirical potentials, and some preliminary simulations results of GBs under mechanical solicitations. Preliminary experimental results on the elaboration and characterization of bicrystals will also be presented.
[1] N. Shibata, F. Oba, T. Yamamoto, and Y. Ikuhara, Philos. Mag. 84, 2381 (2004).
[2] H. Ogawa, Mater. Trans. 47, 2706 (2006).
[3] S. Plimpton, J. Comput. Phys. 117, 1 (1995).
Advances in molecular simulation , Interfacial and confined phenomena
