Zhu Mingke, Wu Ping, Li Qiulin, Xu Ben
School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, P. R. China.
Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, P. R. China.
Sci Rep. 2017 Oct 25;7(1):13964. doi: 10.1038/s41598-017-14398-6.
We investigated the effect of vacancy formation on brittle (D0) to ductile (L1-like) transition in AlTi using DFT calculations. The well-known pseudogap on the density of states of AlTi migrates towards its Fermi level from far above, via a W - M co-doping strategy, where M is Si, Ge, Sn or Pb respectively. In particular, by a W - M co-doping the underline electronic structure of the pseudogap approaches an octahedral (L1: t, e) from the tetragonal (D0: e, b, a, b) crystal field. Our calculations demonstrated that (1) a W-doping is responsible for the close up of the energy gap between a and b so that they tend to merge into an e symmetry, and (2) all M-doping lead to a narrower gap between e and b (moving towards a t symmetry). Thus, a brittle to ductile transition in AlTi is possible by adopting this W - M co-doping strategy. We further recommend the use of W-Pb co-doped AlTi to replace the less anodic Al electrode in Al-battery, due to its improved ductility and high Al diffusivity. Finally this study opens a new field in physics to tailor mechanical properties by manipulating electron energy level(s) towards higher symmetry via vacancy optimization.
我们使用密度泛函理论（DFT）计算研究了空位形成对AlTi中脆性（D0）到韧性（类L1）转变的影响。通过W - M共掺杂策略（其中M分别为Si、Ge、Sn或Pb），AlTi态密度中著名的赝能隙从远高于费米能级的位置向费米能级移动。特别是，通过W - M共掺杂，赝能隙的基础电子结构从四方（D0：e，b，a，b）晶体场接近八面体（L1：t，e）。我们的计算表明：（1）W掺杂导致a和b之间的能隙缩小，使其倾向于合并为e对称性；（2）所有M掺杂导致e和b之间的能隙变窄（向t对称性移动）。因此，采用这种W - M共掺杂策略，AlTi中有可能实现从脆性到韧性的转变。由于其改善的延展性和高Al扩散率，我们进一步建议使用W - Pb共掺杂的AlTi来替代Al电池中阳极活性较低的Al电极。最后，本研究开辟了一个新的物理领域，即通过空位优化将电子能级向更高对称性调控来定制机械性能。
