Ab initio investigation of energetics and stability of vacancy clusters in the FCC high-entropy alloy FeCrCoNi

Abstract

The energetics and stability of divacancy, trivacancy, and tetravacancy of the face-centered cubic (FCC) high entropy alloy (HEA) FeCrCoNi in random solid solutions have been investigated by first-principles calculations and ab initio molecular dynamics simulations. Both the formation energy and the binding energy of the vacancy clusters exhibit a broad and overlapping energy distribution. Unlike pure metals, the local lattice distortion induced by the vacancy defects is irregular, displaying both local volume expansion and contraction in our calculations. According to the results of ab initio molecular dynamics (AIMD) simulations, the examined alloy has a higher probability of defect cluster dissociation compared to pure Ni. The tetravacancies decompose into two smaller vacancy defects of (divacancy+divacancy) in the HEA and (monovacancy+trivacancy) in Ni, respectively. Such characteristics for the small vacancy cluster in the HEA are anticipated to significantly influence aggregation, diffusion, and dissociation in the microstructural evolution of defects under irradiation.