Insight into the vacancy effects on mechanical and electronic properties of VSi silicides from first-principles calculations.

As so far, the development and application prospects of transition metal silicon-based materials have received the considerable attention. V-Si silicides are one of the most important silicon-based high-temperature materials. Brittle behavior hinders their wide application. In present work, the influence of vackancies on mechanical properties, brittle/ductile behavior and electronic properties of VSi silicides is studied using the first-principles calculations. The vacancy formation energy, elastic constants, elastic modulus, brittle/ductile behavior and electronic behavior of the perfect VSi and VSi with vacancies were comparatively calculated and discussed, respectively. The thermodynamic data and phonon frequencies demonstrate that the VSi with different vacancies can exhibit the structural stability. Although the vacancies weaken the hardness of VSi, the vacancies improve the brittle behavior of the parent VSi. Especially, the Si and Si vacancies in VSi induced brittle-to-ductile transition for VSi desilicides. The electronic structures explain the mechanism of the difference of mechanical properties for different vacancies.