Ab initio Approaches to High Entropy Alloys - A comparison of CPA, SQS, and Supercell methods*

High entropy alloys (HEA) are a great approach to multicomponent alloy design with disorder being stabilized by the high configurational entropy.  The most common for these alloys are simple structures (e.g. body-centered cubic) with extremely high chemical disorder. Typically, HEA are composed of four or more principal components to achieve high entropy of mixing, which results in alloys with highly tunable properties.

 

Here, we present a comparison of the three ab-initio approaches to the HfNbTaTiZr and NbZr high entropy alloys: a Coherent Potential Approximation (CPA) method, Supercell method and the Special Quasi-random Structure (SQS). All three approaches are great for describing compositional disorder with their own advantages and disadvantages. CPA is less computationally expensive, when comparing to the SQS and the Supercell methods, since only a small unit cell is required to represent any arbitrary composition of HEA. However, due to the larger simulation cell, SQS and Supercell methods are better for capturing characteristics like extended magnetic and electronic orderings, etc. We will present a comparison of different characteristics along with the comparison of the computational cost for all three methods for HfNbTaTiZr and NbZr high entropy alloy calculations.