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

高熵合金(HEAs)是近10年来提出的一种最具发展前景的新型结构材料。高硬度、高高温强度、高热稳定性以及良好的耐腐蚀性已被报道，然而，尽管进行了大量的实验工作，其基本设计规则以及许多重要的材料性能仍然没有被很好地理解。这特别适用于晶格和磁激发的影响，对相稳定性以及扩散和缺陷性质(如层错能)的影响，并解释了为什么目前的高能电池的设计准则主要基于经验规则，而不是基于对基本物理机制的理解。因此，高能电池是快速增长的集成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，它最初只被设计用于计算基态(T=0K)的性质。到目前为止，通过这种无偏倚、无参数的量子力学模拟，人们对HEAs知之甚少。这是因为直到最近，这些方法才发展到能够充分解决热力学性质的阶段。这个项目将东道主在描述化学有序-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，计算出精心挑选的、非常有前途的HEAs的一组明确的材料性质，包括它们的相稳定性、磁性、层错能和扩散参数。原子论的洞察力有望使根据材料性能要求选择HEA组成成为可能。

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.