Abstract

Vacancy formation in High Entropy Alloys (HEA) is an important aspect of their thermodynamic and kinetic theoretical description. Recent studies have shown that this topic can be approached from the side of density functional theory investigations for some concentrated alloys. However, DFT modeling of vacancy formation in HEA remains a challenging and often too complex task due to large sets of atomic configurations near a point defect that need to be accounted for in the calculations. Another challenge is related to an additional degree of complexity related to the paramagnetic state of some HEA such as the classical equimolar fcc CoCrFeMnNi. In this study, we demonstrate a way to reduce the computational complexity of point defect calculations in HEA and investigate the formation of thermal vacancies in the paramagnetic fcc CoCrFeMnNi alloy using DFT-based models and experimental X- ray diffraction analysis of the alloy crystal structure. We evaluate the effect of the paramagnetic state with respect to standard non-magnetic calculations. The calculated results predict a sizable contribution from the magnetic state with yet minor variations of the effective vacancy formation energy in the range from 1.66 at the room temperature up to 1.76eV at 1373K.

Keywords: High entropy alloys; Point defects; Density functional theory; Paramagnetism; Disordered alloys