First-Principles Study of Vacancies in Ti₃SiC₂ and Ti₃AlC₂

Hui Wang; Han Han; Gen Yin; Chang-Ying Wang; Yu-Yang Hou; Jun Tang; Jian-Xing Dai; Cui-Lan Ren; Wei Zhang; Ping Huai

doi:10.3390/ma10020103

First-Principles Study of Vacancies in Ti₃SiC₂ and Ti₃AlC₂

Materials (Basel). 2017 Jan 25;10(2):103. doi: 10.3390/ma10020103.

Authors

Hui Wang¹, Han Han², Gen Yin³, Chang-Ying Wang⁴, Yu-Yang Hou⁵, Jun Tang⁶, Jian-Xing Dai⁷, Cui-Lan Ren⁸, Wei Zhang⁹, Ping Huai¹⁰

Affiliations

¹ School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471003, China. nkxirainbow@gmail.com.
² Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. hanhanfudan@gmail.com.
³ Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA. genyin@ucla.edu.
⁴ Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. wangchangying@sinap.ac.cn.
⁵ School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471003, China. hyy9539@163.com.
⁶ School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471003, China. Tangjunguyue@126.com.
⁷ Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. daijianxing@sinap.ac.cn.
⁸ Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. rencuilan@sinap.ac.cn.
⁹ Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. zhangwei@sinap.ac.cn.
¹⁰ Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China. huaiping@sinap.ac.cn.

Abstract

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_Ti(a) > V_Ti(b) > V_C > V_A 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_Ti and V_C 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 V_A are introduced. The different effect of V_A on the lattice constants is explained by enhanced interactions of nearby Ti layers.

Keywords: MAX phases; density functional theory; diffusion barrier; vacancies.