Wang Hui, Han Han, Yin Gen, Wang Chang-Ying, Hou Yu-Yang, Tang Jun, Dai Jian-Xing, Ren Cui-Lan, Zhang Wei, Huai Ping
School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471003, China.
Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China.
Materials (Basel). 2017 Jan 25;10(2):103. doi: 10.3390/ma10020103.
MAX phase materials have attracted increased attention due to their unique combination of ceramic and metallic properties. In this study, the properties of vacancies in Ti₃AlC₂ and Ti₃SiC₂, which are two of the most widely studied MAX phases, were investigated using first-principles calculations. Our calculations indicate that the stabilities of vacancies in Ti₃SiC₂ and Ti₃AlC₂ differ greatly from those previously reported for Cr₂AlC. The order of the formation energies of vacancies is V > V > V > V for both Ti₃SiC₂ and Ti₃AlC₂. Although the diffusion barriers for Ti₃SiC₂ and Ti₃AlC₂ are similar (~0.95 eV), the properties of their vacancies are significantly different. Our results show that the vacancy-vacancy interaction is attractive in Ti₃AlC₂ but repulsive in Ti₃SiC₂. The introduction of V and V vacancies results in the lattice constant along the [0001] direction increasing for both Ti₃SiC₂ and Ti₃AlC₂. In contrast, the lattice constant decreases significantly when V are introduced. The different effect of V on the lattice constants is explained by enhanced interactions of nearby Ti layers.
MAX相材料因其陶瓷和金属特性的独特组合而受到越来越多的关注。在本研究中，使用第一性原理计算研究了Ti₃AlC₂和Ti₃SiC₂（两种研究最广泛的MAX相）中空位的性质。我们的计算表明，Ti₃SiC₂和Ti₃AlC₂中空位的稳定性与先前报道的Cr₂AlC有很大不同。对于Ti₃SiC₂和Ti₃AlC₂，空位形成能的顺序均为V > V > V > V。尽管Ti₃SiC₂和Ti₃AlC₂的扩散势垒相似（约0.95 eV），但其空位性质却有显著差异。我们的结果表明，空位 - 空位相互作用在Ti₃AlC₂中具有吸引力，而在Ti₃SiC₂中具有排斥力。V和V空位的引入导致Ti₃SiC₂和Ti₃AlC₂沿[0001]方向的晶格常数增加。相反，引入V时晶格常数会显著减小。V对晶格常数的不同影响是由附近Ti层相互作用增强来解释的。
