Centre for Computational Molecular Science, Australian Institute for Bioengineering and Nanotechnology, University of Queensland, Brisbane QLD 4072, Australia.
Phys Chem Chem Phys. 2013 Oct 28;15(40):17553-9. doi: 10.1039/c3cp52245h.
A theoretical model is proposed to determine the effects of Si substitution with Al on the oxygen diffusion in apatite-type lanthanum silicates based on density-functional theory (DFT) calculations for La10(SiO4)4(AlO4)2O2. Substitution changes the stable configuration for excess oxygen from the split interstitial to a new cluster form with the original cluster. Al doping completely changes the migration mechanism from the interstitialcy one, which was proposed for the La9.33(SiO4)6O2 starting material, to a mechanism which contains an interstitial process. Nevertheless, the migration barrier is calculated to be 0.81 eV, which indicates small changes in oxygen conduction and is consistent with the observations. The present study indicates that the cation substitution on silicon site alone does not promise the improvement of the oxide ion conduction in the lanthanum silicate.
提出了一个理论模型，以基于密度泛函理论（DFT）计算来确定 Si 取代 Al 对磷灰石型镧硅酸盐中氧扩散的影响。取代作用将过剩氧的稳定构型从分裂的间隙位置改变为具有原始簇的新簇形式。Al 掺杂完全改变了迁移机制，对于 La9.33（SiO4）6O2 起始材料，该机制提出了一种间隙机制，而现在的机制包含了一个间隙过程。然而，迁移势垒被计算为 0.81 eV，这表明氧传导的变化很小，与观察结果一致。本研究表明，仅在硅位上的阳离子取代并不能提高镧硅酸盐中的氧离子传导。
