The influence of vacancy defects on elastic and electronic properties of TaSi (5/3) desilicides from a first-principles calculations

As so far, the investigation and application of transition metal silicon-based materials have attracted wide attention. Tantalum-based silicides are one of the most important silicon-based high-temperature materials. But the brittle behavior hinders their wide applications. Here, the influence of vacancies on mechanical properties, brittle/ductile behavior and electronic properties of Ta5Si3 desilicides has been investigated using the firstprinciples calculations. The vacancy formation energy, elastic constants, elastic moduli, brittle/ductile behavior and electronic behavior of the perfect Ta5Si3 and Ta5Si3 with vacancies were comparatively calculated and discussed, respectively. The thermodynamic data and phonon dispersions demonstrate that the available Ta vacancies in Ta5Si3 can exhibit the better stability than Si atomic vacancies in Ta5Si3 desilicides. In addition, although the vacancies weaken the hardness of the parent Ta5Si3, the vacancies improve the brittle behavior of the parent Ta5Si3. Especially, the Ta-va1 vacancy in Ta5Si3 induced brittle-to-ductile transition for parent Ta5Si3 desilicides. The electronic structures explain the mechanism of the different vacancies effect on mechanical properties.