Materially-Predictive Theory of Magnetic Behavior and the Heavy Fermion State

磁行为和重费米子态的材料预测理论

• 批准号: 9120333
• 负责人: Bernard Cooper
• 金额: $ 23.2万
• 依托单位: West Virginia University Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-12-01 至 1995-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9120333&HistoricalAwards=false
• 关键词: Materially; Predictive; Theory; Magnetic; Behavior

This research is aimed at exploiting and extending capabilities for treating the reduced magnetic ordering and related phenomena, including magneto-optic behavior, associated with the highly correlated f-electron state on approaching or being in the heavy fermion state. Essentially, we have learned how to exhibit magnetic ordering properties in the correlated-electron state by projecting onto a site-centered basis. Our materially-predictive methodology involves two major stages: (1) the parameters in a lattice model hamiltonian containing both band-f hybridization and band-f coulomb exchange are calculated by a sequence of electronic structure calculations and, (2) a two-step sequence for finding the magnetic ordering properties (ground state and equilibrium behavior, magnetic excitations, critical behavior) first transforming the model hamiltonian into the language of resonant scattering theory to get an effective multipolar two-ion interaction and then using various methods we have developed to predict the observable properties on a wholly ab initio basis (no adjustable parameters or empirical information used). We will use this methodology to predict the approach to and nature of magnetic ordering in the heavy fermion state for seveal isostructural systems of experimental interest. Our methodology will be extended to include predicting (1) incremental specific heat associated with magnetic ordering, (2) pressure effects and elastic properties, (3) effects in high applied magnetic fields, (4) alloying including diluting the f-electron species. In addition, we will initiate studies on the role of explicit (interconfigurational) correlation effects on the magneto-optic behavior and on the conduction bands. %%% Computationally-intensive research will be undertaken to study the magnetic properties of materials in which the electrons behave as if their masses are many times their usual mass, ie, so-called heavy fermion systems. These highly correlated systems are difficult to treat using conventional techniques. The calculations proposed here are unique in coupling electronic structure calculations for these systems with many-body theory to describe these highly correlated systems from a first-principles approach.

这项研究的目的是开发和扩展处理与高关联f电子态接近或处于重费米子态时减少的磁有序和相关现象，包括磁光行为的能力。从本质上讲，我们已经学会了如何通过投射到以位置为中心的基础上来展示关联电子态的磁有序性质。我们的物质预测方法包括两个主要阶段：(1)包含带-f杂化和带-f库仑交换的晶格模型哈密顿量中的参数通过一系列电子结构计算来计算，以及(2)用于寻找磁有序性质(基态和平衡行为，磁激发，临界行为)首先将模型哈密顿量转换为共振散射理论的语言，以得到有效的多极两离子相互作用，然后使用我们开发的各种方法在完全从头计算的基础上(不使用可调参数或经验信息)来预测可观测性质。我们将使用这种方法来预测几个实验感兴趣的等结构系统在重费米子态下的磁性有序的方法和性质。我们的方法将扩展到包括预测(1)与磁有序有关的增量比热，(2)压力效应和弹性性质，(3)高外加磁场中的效应，(4)合金化，包括稀释f电子物种。此外，我们还将开始研究显性(组态间)关联效应对磁光行为和导带的作用。将进行计算密集的研究，以研究材料的磁性，在这些材料中，电子的行为就像它们的质量是其通常质量的许多倍一样，即所谓的重费米子系统。这些高度相关的系统很难使用传统技术进行治疗。在将这些体系的电子结构计算与多体理论相结合，从第一性原理方法描述这些高度关联的体系方面，这里提出的计算是独一无二的。