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Open AccessArticle

First-Principles Study of Vacancies in Ti3SiC2 and Ti3AlC2

1
School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471003, China
2
Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
3
Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA
*
Authors to whom correspondence should be addressed.
Academic Editor: Duncan H. Gregory
Materials 2017, 10(2), 103; https://doi.org/10.3390/ma10020103
Received: 23 December 2016 / Revised: 18 January 2017 / Accepted: 23 January 2017 / Published: 25 January 2017
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 VTi(a) > VTi(b) > VC > VA 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 VTi and VC vacancies results in the lattice constant c along the [0001] direction increasing for both Ti3SiC2 and Ti3AlC2. In contrast, the lattice constant c decreases significantly when VA are introduced. The different effect of VA on the lattice constants is explained by enhanced interactions of nearby Ti layers. View Full-Text
Keywords: MAX phases; vacancies; diffusion barrier; density functional theory MAX phases; vacancies; diffusion barrier; density functional theory
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MDPI and ACS Style

Wang, H.; Han, H.; Yin, G.; Wang, C.-Y.; Hou, Y.-Y.; Tang, J.; Dai, J.-X.; Ren, C.-L.; Zhang, W.; Huai, P. First-Principles Study of Vacancies in Ti3SiC2 and Ti3AlC2. Materials 2017, 10, 103.

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