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

高熵合金是近10年来出现的新型结构材料之一。尽管有大量的实验研究，但人们对高硬度、高强度、热稳定性和耐腐蚀性等材料的基本设计规则以及许多重要的材料性能仍不甚了解。这特别适用于晶格和磁激发的影响，相稳定性以及扩散和缺陷性质（如堆垛层错能），并解释了为什么HEAs的当前设计标准主要是基于经验规则，而不是基于对底层物理机制的理解。因此，HEAs是快速增长的集成计算材料工程领域的理想候选人。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，它最初被设计为仅计算基态（T=0 K）性质。到目前为止，很少有人知道HEAs从这种无偏的，无参数的量子力学模拟。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。该项目将主机在描述化学有序-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起来，计算精心挑选的高度有前途的HEAs的一组定义良好的材料性质，包括它们的相稳定性，磁性，堆垛层错能和扩散参数。原子论的见解，预计可以选择HEA组合物的材料性能要求的指导。

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.