npj： 结构材料孪晶晶界的稳定性

原子缺陷对金属材料的机械性能影响至关重要。孪晶是发生在某一区域的原子规则排列的错排，在六方密堆积结构中其缺陷原子结构的形成至今难以解释，包括孪生晶界的本征结构及其稳定性，多年来一直存在争议。来自德国和捷克的研究人员运用从头算方法和大规模原子模拟，揭示了镁金属中可能出现的两种类型孪晶：滑移孪晶和反射孪晶，并发现力学不稳定性决定孪生晶界结构，使滑移孪晶很难在实验中观察到。该文近期发表于npj Computational Materials 3: 6 (2017)，其标题与摘要如下，点击阅读原文可以自由获取。

We have investigated twin boundaries in double-lattice hexagonal close-packed metallic materials, focusing on their atomic geometry. Combining accurate ab-initio methods and large-scale atomistic simulations we address the following two fundamental questions: (i) What are the possible intrinsic twin boundary structures in hcp crystals? (ii) Are these structures stable against small distortions? In order to help end a decade-long controversy over the experimental observations of the atomic structures of twin boundaries, we have determined the energetics, spectra, and transition mechanisms of the twin boundaries. Our results confirm that the mechanical stability controls structures which are observed.