The Study of Nickel Impurity Segregation on LSNT Perovskite Open Surfaces by Ab Initio Molecular Dynamics

In this paper, the segregation of an Ni impurity on open surfaces of doped strontium titanate perovskite is investigated by the ab initio molecular dynamics method based on the density functional theory and applied to a model periodic cell with stoichiometry $${\text{L}}{{{\text{a}}}_{{{\text{0}}{\text{.5}}}}}{\text{S}}{{{\text{r}}}_{{{\text{0}}{\text{.5}}}}}{\text{Ti}}{{{\text{O}}}_{{\text{3}}}}$$ (LST). The studies are based on recent experimental observations on the segregation of Ni impurity atoms and their tendency to form clusters at the boundaries of $${\text{L}}{{{\text{a}}}_{{{\text{0}}{\text{.2}}}}}{\text{S}}{{{\text{r}}}_{{{\text{0}}{\text{.7}}}}}{\text{N}}{{{\text{i}}}_{{{\text{0}}{\text{.1}}}}}{\text{T}}{{{\text{i}}}_{{{\text{0}}{\text{.9}}}}}{{{\text{O}}}_{{3 - \delta }}}$$ (LSNT) perovskite structure defects. The results of the first-principles calculations of segregation energy showed that Ni actively segregates toward the open surfaces. It is found that during segregation, nickel atoms leave the crystal volume toward the perovskite surface and rise above its upper layer. Thus, the obtained results confirm the experimental data on the segregation and formation of nickel clusters on open LSNT surfaces.

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