Investigation Of Point Defects By First-principles Calculations In M₃AX₂ Materials

The point defect of M3AX2 phases have been calculated using first-principles calculations. The aim of the calculations is explore structural stability and irradiation resistance of M3AX2 phases materials. M3AX2 phases materials includes Ti3AlC2> Ti3SiC2、Ti3GeC2 and Ta3AlC2. The results of calculations clarify that vacancy defect is of great significance in terms of crystal structure under irradiation.Firstly, we calculated lattice parameters of Ti3AlC2 material. The result is consistent with the experimental results and ensure the accuracy of this calculation. Secondly, we calculated elastic constants and elastic modulus of M3AX2 phases materials. The results prove their stability and preliminary estimate their interaction and bonding between atoms. Based on previous conclusions, the formation and migration energies of the mono-vacancies in M3AX2. By analyzing the results, we draw an important conclusion that M atomic layer (including M1 and M2) is the lowest active. M vacancy was found to preferentially form in the M2 layer close to A layer. Density of state and electron density were calculated to verify the conclusion from interaction and bonding between atoms.The formation energy of helium interstitial atom (mono-interstitial and bi-interstitial) was calculated. Ti3SiC2 material has a better irradiation resistance because of the higher formation energy. The above results contribute to study structural stability and irradiation resistance of M3AX2 materials.