npj: 氧化钛电子化合物材料—预测的电子新位置

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电子化合物材料是一种以电子作为阴离子的特殊离子晶体材料，与传统金属材料不同，其内部电子并不随机自由分布，其分布具有一定的区域性。新型无机电子化合物材料因在透明导体、电池电极、电子发射器以及化学合成催化中的重要潜在应用，其相关研究引起了科学工作者的广泛关注。然而先前制备的有机电子化合物材料热稳定性较差，严重制约电子化合物材料的发展。到目前为止仅成功合成了少量无机电子化合物材料，用作电子化合物材料的实例更是极为有限。

针对以上问题，来自中国吉林大学马琰铭教授课题组利用自主研发的CALYPSO方法与软件，研究提出了通常用作涂料和防晒剂的二氧化钛（TiO₂）转而用作电子材料的可能性，探索了Ti-O体系在高压下不同化学计量配比的晶体结构。研究结果指出除已知的TiO₂外，在富Ti区，Ti_xO（x=2-6）都能形成稳定的电子材料，揭示了当金属Ti的含量超过O的两倍以上，价电子转移到晶格间隙，形成了新型电子化合物材料。本工作不仅提供了压力诱导形成反常规计量化学配比电子材料的典型范例，还表明了CALYPSO方法和软件在新型功能材料设计领域发挥着越来越重要的作用。

该文近期发表于npj Computational Materials 4: 70 (2018)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Predicting the structure and stability of titanium oxide electrides 

Xin Zhong, Meiling Xu, Lili Yang, Xin Qu, Lihua Yang, Miao Zhang, Hanyu Liu & Yanming Ma 

The search for new inorganic electrides has attractedsignificant attention due to their potential applications in transparentconductors, battery electrodes, electron emitters, as well as catalysts forchemical synthesis. However, only a few inorganic electrides have beensuccessfully synthesized thus far, limiting the variety of electride examples. Here,we show the stabilization of inorganic electrides in the Ti-rich Ti–O systemthrough first-principles calculations in conjunction withswarm-intelligence-based CALYPSO method for structure prediction. Besides theknown Ti-rich stoichiometries of Ti₂O, Ti₃O, and Ti₆O,two hitherto unknown Ti₄O and Ti₅O stoichiometries arepredicted to be thermodynamically stable at certain pressure conditions. Wefound that these Ti-rich Ti–O compounds are primarily zero-dimensionalelectrides with excess electrons confined in the atom-sized lattice voids orbetween the cationic layers playing the role as anions. The underlyingmechanism behind the stabilization of electrides has been rationalized in termsof the excess electrons provided by Ti atoms and their accommodation of excesselectrons by multiple cavities and layered atomic packings. The present results provide a viable direction for searching for practicalelectrides in the technically important Ti–O system.

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