A molecular dynamics study of the local structure evolution with temperature in Gd-doped CeO2: Focus on the bond length

Since the long-range structure of the Gd-doped system (Ce1−xGdxO2−x/2) remains in the fluorite structure in the x-range [0–0.3], it is of interest to study this system in the local range. Molecular dynamics simulations seem to be particularly suitable for this purpose. Among all the possible parameters used to describe the local order/disorder, we focus on the behavior of the bond lengths. Doping cations and oxygen vacancies are introduced inside the fluorite structure following two arrangements, the random (R) and the neighbor (N). We investigate the evolution of the bond lengths with the temperature and doping level and identify different trends depending on the bond type (cation–anion, cation–cation). The bond length thermal expansion can be drastically different from the long-range thermal expansion mainly for the bonds implying Gd3+ cation. The presence of C-type Gd2O3 clusters is discussed through the study of the double component of the Gd–Gd Radial Distribution Function. Comments are provided for evolution of distances beyond the first and second shells of the cations’ environment. This study also demonstrates the impact of point defect distribution (R or N) on the evolution of the local structure, while maintaining the long-range fluorite structure.