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

高熵合金（High entropy alloys, HEAs）是十多年前问世的一种新型结构材料。许多非常理想的性能已被报道，如高硬度，高温强度和热稳定性以及良好的耐腐蚀性。然而，尽管进行了大量的实验工作，但它们的基本设计规则以及许多重要的材料特性仍然没有得到很好的理解。这尤其适用于晶格和磁激励、相稳定性以及扩散和缺陷特性（如层错能）的影响，并解释了为什么目前HEAs的设计标准主要基于经验规则，而不是基于对潜在物理机制的理解。因此，HEAs是快速发展的综合计算材料工程领域的理想候选者。在这种方法中，在电子结构水平上应用最广泛的方法是密度泛函理论，该理论最初被设计用于计算基态（T=0 K）性质。到目前为止，从这种无偏、无参数的量子力学模拟中，人们对高能粒子知之甚少。这是因为直到最近，这些方法才发展到允许充分解决热力学性质的阶段。该项目将宿主在描述化学有序-无序现象方面的独特专业知识和申请人在有限温度磁性方面的独特专业知识结合在一起，以计算精心挑选的、极有前途的HEAs的一组定义良好的材料特性，包括它们的相稳定性、磁性能、层错能和扩散参数。原子论的见解有望使根据材料性能要求选择HEA成分成为可能。

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.