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首页> 外文期刊>Journal of Materials Chemistry, A. Materials for energy and sustainability >Growth of nano-domains in Gd-CeO2 mixtures: hybrid Monte Carlo simulations
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Growth of nano-domains in Gd-CeO2 mixtures: hybrid Monte Carlo simulations

机译：Gd-CeO2混合物中纳米域的生长：混合蒙特卡洛模拟

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Hybrid Monte Carlo (HMC) simulations are used to study the growth of Gd-rich domains in Gd doped CeO2, and we probe the conductivity of the resulting and other configurations by molecular dynamics. Previous work has been restricted to the dilute defect limit, assumptions of particular cluster formation, and neglect of all temperature effects. Our methods suffer none of these restrictions. Even at low concentrations Gd3+ segregates into domains. We have examined the local environment of the Gd3+ ions using radial distribution functions and Steinhardt order parameters. The observed structure is consistent with the formation of cubic C-type (Gd2O3) domains, rather than the monoclinic B-type or pyrochlore clusters which have been suggested previously. In addition, previous detailed pair distribution function analysis of the solid solution has indicated different local cation environments from those from a Rietveld analysis - overall our results support the former analysis rather than the latter. At the elevated temperatures (1000 K) of the simulations there is no particular preference for vacancy and dopant cations to be located at second neighbour sites, an issue long discussed for this and similar systems. Both calculated and experimental conductivities show a similar variation with composition, passing through a maximum with increasing Gd concentration. The conductivities of the configurations generated in the hybrid Monte Carlo simulations are lower than those of configurations generated independently in which the Gd ions are distributed at random. The HMC thermally generated Gd nano-domains capture oxygen vacancies, reduce oxygen vacancy mobility and block diffusion paths.
机译：混合蒙特卡罗（HMC）模拟用于研究掺Gd的CeO2中富Gd域的生长，并且我们通过分子动力学来研究所得构型和其他构型的电导率。以前的工作仅限于稀释缺陷极限，特定团簇形成的假设以及对所有温度影响的忽略。我们的方法不受这些限制。即使在低浓度下，Gd3 +也会分离成域。我们已经使用径向分布函数和Steinhardt有序参数检查了Gd3 +离子的局部环境。观察到的结构与立方C型（Gd2O3）域的形成是一致的，而不是先前提出的单斜B型或烧绿石簇。此外，先前对固溶体进行的详细的偶对分布函数分析表明，其局部阳离子环境与Rietveld分析的局部阳离子环境不同-总体而言，我们的结果支持前一种分析，而不是后者。在模拟的高温（1000 K）下，对于位于第二相邻位置的空位和掺杂阳离子没有特别的偏好，这个问题和类似系统早已讨论过。计算出的电导率和实验电导率均显示出相似的组成变化，随着Gd浓度的增加而达到最大值。混合蒙特卡罗模拟中生成的构型的电导率低于Gd离子随机分布的独立生成的构型的电导率。 HMC热生成的Gd纳米域捕获氧空位，降低氧空位迁移率并阻止扩散路径。

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