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First-principles study and modeling of strain-dependent ionic migration in ZrO_2

机译：ZrO_2中依赖应变的离子迁移的第一性原理研究与建模

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Electrolytes with high ionic conductivity at lower temperatures are the prerequisite tor the success or Solid Oxide Fuel Cells (SOFC). One promising candidate is doped zirconia. In the past its ionic conductivity has mainly been increased by decreasing its thickness. However, the influence of the thickness is only linear, whereas the impact of migration barriers is exponential. Therefore understanding the oxygen transport in doped zirconia is of fundamental importance. In this work we pursue the approach of the strain dependent ionic migration in zirconia. We investigate how the migration barriers for oxygen ions respond to a change of the atomic strain. We employ the method of Density Functional Theory (DFT) calculations to relax the atomic configurations to the ground state. In connection with the Nudged Elastic Band (NEB) method we obtain the migration barrier of the oxygen ion jumps in zirconia for a given lattice constant. Similar to other publications we observe a decrease in the migration barrier for expansive strain, but in addition we also find a migration barrier decrease for high compressive strains beyond a maximal height of the migration barrier at an intermediate compressive strain. We present a simple analytic model which, by using interactions of the Lennard-Jones type, gives an explanation for this behavior.
机译：固体氧化物燃料电池（SOFC）的成功是在较低温度下具有高离子电导率的电解质。一种有希望的候选物是掺杂的氧化锆。过去，其离子电导率主要是通过减小其厚度来增加的。但是，厚度的影响只是线性的，而迁移壁垒的影响是指数的。因此，了解掺杂氧化锆中的氧传输至关重要。在这项工作中，我们追求氧化锆中应变依赖性离子迁移的方法。我们调查氧离子的迁移壁垒如何响应原子应变的变化。我们采用密度泛函理论（DFT）计算方法将原子构型放宽至基态。结合微动弹性带（NEB）方法，对于给定的晶格常数，我们获得了氧化锆中氧离子跃迁的迁移势垒。与其他出版物类似，我们观察到膨胀应变的迁移势垒降低，但除此之外，我们还发现，在中等压缩应变时，超出最大迁移势垒高度的高压缩应变，迁移势垒降低。我们提出了一个简单的分析模型，该模型通过使用Lennard-Jones类型的交互作用，对此行为进行了解释。

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