Local charge distortion due to Cr in Ni-based concentrated alloys

Abstract

Due to the presence of multiple elements consisting of a range of atomic radii, local lattice distortion (LLD) is commonly observed in concentrated (and high entropy) alloys. However, since these elements also have diverse electronegativities, recent works show that atoms can have a range of atomic charges. In this work, using density functional theory (DFT), we investigate electronic charge distribution in face centered cubic (FCC) Ni-based alloys and find significant charge-density distortion in HEAs. Specifically, Cr atoms have large charge density distortion that results in a wide range of bond lengths, atomic charges, and electronic density of states in Cr-containing alloys. The charge distortion impacts the stacking fault energies (SFEs) as a wide range of SFEs are observed in Cr-containing alloys (e.g., NiCr, NiFeCr and NiCoCr), which are otherwise narrow and converged in non-Cr containing alloys such as NiFe, NiCo and NiFeCo. These observations provide insights into the role of local charge distortion towards local lattice distortion in HEAs and illustrate the effect of charge distortion on the mechanical properties of the alloys.