npj：缺陷——基于第一性原理研究金属钛中的杂质

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钛合金由于兼具强度、密度和耐腐蚀性等特性，被广泛用于航空和生物医用行业。通过近几十来的实验研究，人们对其工艺-微结构-性能间关系有了深刻认识。点缺陷对于钛合金的力学性能影响举足轻重，然而目前对于点缺陷的认识尚处在半经验理论层面。来自美国康涅狄格大学的Sanjeev Nayak和Rainer Herbert教授等采用第一性原理计算研究了金属钛中的本征和外来点缺陷的稳定性，其中包括元素周期表中前20种化学元素，以及金属钛中通常添加的过渡金属元素。他们发现，强电负性杂质元素，如C、N、O、F、S和Cl等，不论其原子半径大小均倾向占据钛晶格的八面体间隙位。而金属杂质如钒等，则倾向占据替代位。晶格中的空位只有在远离钛间隙原子时才能稳定存在。这些研究结果将有助我们调控材料用于诸如3D打印等各种先进制造工艺。该研究近期发表于npj Computational Materials 4: 11 (2018);  doi:10.1038/s41524-018-0068-9。英文标题与摘要如下，点击阅读原文可以自由获取论文PDF。

Insight into point defects and impurities in titanium from first principles

Sanjeev K.Nayak, Cain J. Hung, Vinit Sharma, S. Pamir Alpay, Avinash M.Dongare, William J.Brindley & Rainer J.Hebert

Titanium alloys find extensive use in the aerospace and biomedical industries due to a unique combination of strength, density, and corrosion resistance. Decades of mostly experimental research has led to a large body of knowledge of the processing-microstructure-properties linkages. But much of the existing understanding of point defects that play a significant role in the mechanical properties of titanium is based on semi-empirical rules. In this work, we present the results of a detailed self-consistent first-principles study that was developed to determine formation energies of intrinsic point defects including vacancies, self-interstitials, and extrinsic point defects, such as, interstitial and substitutional impurities/dopants. We find that most elements, regardless of size, prefer substitutional positions, but highly electronegative elements, such as C, N, O, F, S, and Cl, some of which are common impurities in Ti, occupy interstitial positions.

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