Novel potentials for modelling defect formation and oxygen vacancy migration in Gd2Ti2O7 and Gd2Zr2O7 pyrochlores
Novel potentials for modelling defect formation and oxygen vacancy migration in Gd2Ti2O7 and Gd2Zr2O7 pyrochlores
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DOI：
10.1039/c2jm15264a
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发表时间：
2012-01-01
影响因子：
--
通讯作者：
Travis, Karl P.
中科院分区：
文献类型：
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作者：
Gunn, David S. D.;Allan, Neil L.;Travis, Karl P.
陶瓷材料在核废料的安全长期固定方面发挥着关键作用，需要对辐射损伤和愈合过程有基本的了解，以便确定拟议的储存材料（如高温超导体）的适用性。在这里，新的原子间相互作用势推导出的高温超导体Gd2Ti2O7和Gd2Zr2O7。他们的准确性和鲁棒性证明，通过计算和比较值的选择点缺陷与使用其他出版的潜力的选择计算。Frenkel对缺陷的形成能量显着降低在少量的局部阳离子无序的存在下。用改进的切向轻推弹性带方法计算了Ti和Zr高温超导体中相邻O_（48）f位之间氧空位迁移的激活能。该能量对于无缺陷Ti比对于Zr烧绿石低类似于0.1eV，与测试的大多数电势一致。对于Gd2Ti2O7，局部阳离子无序对V-O 48f-> V-O 48f迁移能量的影响最小，而相比之下，对于Gd2Zr2O7，迁移能量通常降低约43%。由于这些烧绿石的愈合机制很可能依赖于氧空位的可用性，有缺陷的Zr烧绿石的愈合被预测为比等效的Ti烧绿石更快。
Ceramic materials play a critical role in the safe long-term immobilisation of nuclear waste and fundamental understanding of both radiation damage and healing processes are required in order to determine the suitability of proposed storage materials, such as pyrochlores. Here, new interatomic potentials are derived for the pyrochlores Gd2Ti2O7 and Gd2Zr2O7. Their accuracy and robustness is demonstrated by calculating and comparing values for a selection of point defects with those calculated using a selection of other published potentials. Frenkel pair defect formation energies are substantially lowered in the presence of a small amount of local cation disorder. The activation energy for oxygen vacancy migration between adjacent O48f sites is calculated for Ti and Zr pyrochlores using an improved tangent nudged elastic band method. This energy is lower for the non-defective Ti than for the Zr pyrochlore by similar to 0.1 eV, consistent with the majority of the potentials tested. The effect of local cation disorder on the V-O48f -> V-O48f migration energy is minimal for Gd2Ti2O7, while in contrast the migration energy is lowered typically by similar to 43% for Gd2Zr2O7. Since the healing mechanisms of these pyrochlores are likely to rely upon the availability of oxygen vacancies, the healing of a defective Zr pyrochlore is predicted to be faster than for the equivalent Ti pyrochlore.