First-Principles Study of Vacancies in Ti₃SiC₂ and Ti₃AlC₂

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

Publisher： MDPI

E-ISSN： 1996-1944|10|2|103-103

ISSN： 1996-1944

Source： Materials, Vol.10, Iss.2, 2017-01, pp. : 103-103

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

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.