Melting and superionic transition of Gd-doped ceria nanocrystals: Molecular dynamics study

Abstract

Molecular dynamics program for simulation of nanocrystals in vacuum, with ionic model approximation, was developed. The use of graphics processor allows us to speed up calculation by two orders of magnitude in comparison with CPU realization. For Ce1−XGdXO2−X/2 system by fitting to experimental data pair interaction potentials were obtained, comparison with existing potential set was carried out. Melting temperature of CeO2 nanocrystal depends on its octahedron diagonal size as Тm(L,nm)=Тm(∞)−(5534±153)⋅L−2.Structural disorder of Ce1−XGdXO2−X/2 nanocrystals (X=0–0.3) in superionic transition and melting regimes was investigated. Dependences of melting temperature and specific volume change at melting from gadolinium dopant quantity have downward trend. It is shown, that oxygen sublattice disorder (“melting”) in crystallites takes place at about 0.7Tm. The contribution of intrinsic disorder to anion diffusion coefficient in systems with gadolinium dopant was extracted and the presence of superionic transition is shown. Comparison with high-temperature ionic conductivity data was carried out.