The effect of Zr doping on the structural property and helium behavior of Ti3SiC2 by first-principles study

The effects of Zr doping on the properties of the Ti3SiC2 MAX phase and the behavior of helium are investigated by first-principles calculations. The doping of Zr at different non-equivalent Wyckoff positions, including Ti1 and Ti2, in the Ti3SiC2 is considered. The lattice parameters and the interlayer spacing of Ti3SiC2 are slightly expanded due to the substitution of Ti by Zr. Compared with Ti1 positions, the substitution of Ti-2 positions by Zr has a greater impact on the electronic properties of the Ti3SiC2 system. Meanwhile, He interstitials energetically prefer to occupy the Ti2-Si layer for both the Zr-substituted and the original Ti3SiC2 systems. And the interaction between He and its nearby atoms is weakened more dramatically with Zr doping into Ti-2, compared to Ti1. This results in the solution energy of He interstitials decreasing upon Zr substitution for Ti in Ti3SiC2, especially, the substitution of Zr for Ti2. The doped Zr may play a positive role in the resistance of Ti3SiC2 to helium damage.