Ab initio study of high entropy alloys: Ground state properties and beyond

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High entropy alloys (HEAs), which were introduced about 10 years ago, represent one of the most promising novel classes of structural materials. Many highly desirable properties have been reported such as high hardness, high-temperature strength and thermal stability as well as good corrosion resistance.However, despite huge experimental efforts, their fundamental design rules as well as many important materials properties are still not well understood. This particularly applies to the impact of lattice and magnetic excitations, to phase stabilities as well as to diffusion and defect properties (such as stacking fault energies) and explains why the current design criteria of HEAs are mainly based on empirical rules rather than on an understanding of the underlying physical mechanisms.The HEAs are therefore ideal candidates for the rapidly growing field of integrated computational materials engineering. Within this approach the most widely applied method on the electronic structure level is the density-functional theory, which originally has been designed to compute ground state (T=0 K) properties only. So far very little is known about the HEAs from such unbiased, parameter-free quantum mechanical simulations. This is because only very recently the methods have evolved to a stage allowing to adequately address thermodynamic properties.This project brings the unique expertise of the host in describing chemical order-disorder phenomena and of the applicant in finite-temperature magnetism together to compute a well-defined set of materials properties of carefully selected, highly promising HEAs including their phase stabilities, magnetic properties, stacking fault energies and diffusion parameters. The atomistic insights are expected to make it possible to select HEA composition guided by materials property requirements.