Ab Initio Calculations in Correlated Electron Models and Materials

该奖项支持计算和理论研究以及教育活动，以提高我们对计算材料特性的理解和能力。在由许多粒子组成的量子系统中，精确和预测的计算是科学上的一个巨大挑战。在这些系统中，竞争趋势的微妙平衡创造了物质新阶段和集体现象的丰富可能性，这为具有重大技术重要性的非凡材料特性提供了潜力。然而，这种丰富性和复杂性也意味着通常的定量计算工具将趋于崩溃。方法学的发展和高性能计算的出现相结合，现在为在这个问题上取得根本进展提供了前所未有的机会。这项研究将建立在量子多粒子模拟方法的最新进展上，为催化这一进展贡献一个独特的组成部分。本研究旨在推进具有强电子-电子相互作用的材料的研究，建立准确的基准计算，增强凝聚态体系中直接、多粒子无参数计算的能力。所开发的理论框架和技术也可以在核物理、超冷原子物理和量子化学中产生交叉影响。PI将继续将研究与教育和推广活动结合起来，指导本科生和研究生进行研究，将本项目的材料纳入课程，接触少数民族学生，并促进计算科学教育和研究中的跨学科合作。在更大的科学界，PI将继续在通过学校和研讨会培训学生、博士后和高级研究人员方面发挥积极作用，并开发软件包和教程，用于实践学习新的理论和计算方法以及强相互作用电子系统的性质。技术概述：该奖项支持辅助场量子蒙特卡罗和相关电子系统计算方法的应用和进一步发展的研究和教育活动。这项研究计划的长期目标是能够以更准确和可预测的方式进行多体模拟，以解决结构相变、磁顺序和超导性等问题。在实际材料上进行特定材料的计算和简化模型的研究。将开发新的能力来扩展可处理的系统尺寸，进一步提高精度，计算激发态和响应特性，并处理自旋轨道耦合。计算机模拟相互作用的多费米子系统的主要困难是符号或相位问题。约束路径或无相位辅助场量子蒙特卡罗方法为从头计算材料模拟（作为超越标准密度泛函计算的方法）和强相关系统的晶格模型计算提供了一般框架。可以预期，开发成功的影响将超出所研究的具体系统。PI将继续将研究与教育和推广活动结合起来，指导本科生和研究生进行研究，将本项目的材料纳入课程，接触少数民族学生，并促进计算科学教育和研究中的跨学科合作。在更大的科学界，PI将继续在通过学校和研讨会培训学生、博士后和高级研究人员方面发挥积极作用，并开发软件包和教程，用于实践学习新的理论和计算方法以及强相互作用电子系统的性质。

NON-TECHNICAL SUMMARYThis award supports computational and theoretical research and education activities to advance our understanding of and capabilities to compute materials properties. Accurate and predictive calculations in quantum systems composed of many particles are a grand challenge in science. In these systems the delicate balance of competing tendencies creates rich possibilities of new phases of matter and collective phenomena, which offer the potential for remarkable material properties of great technological importance. This very richness and complexity, however, also means that the usual tools for quantitative calculations will tend to break down. The combination of methodological developments and the advent of high performance computing present an unprecedented opportunity to make fundamental progress in this problem now. The research will build on recent advances in a quantum many-particle simulation approach to contribute a unique component for catalyzing this progress.This research aims to advance the study of materials with strong electron-electron interactions, establish accurate benchmark calculations, and enhance the capabilities of direct, many-particle parameter-free computations in condensed matter systems. The theoretical framework and techniques developed can also have cross-cutting impact in nuclear physics, ultracold atom physics, and quantum chemistry.The PI will continue to integrate research with education and outreach activities, by mentoring both undergraduate and graduate students in research, incorporating materials from this project into courses, reaching out to minority students, and fostering interdisciplinary collaboration in computational science education and research. In the larger scientific community, the PI will continue to play an active role in training students, post-docs, and senior researchers through schools and workshops, and develop software packages and tutorials for hands-on learning of new theoretical and computational approaches and the properties of strongly interacting electron systems.TECHNICAL SUMMARYThis award supports research and educational activities on the application and further development of the auxiliary-field quantum Monte Carlo and related methods for calculations in correlated electron systems. The long-term goal of this research program is the ability to perform many-body simulations to address questions on structural phase transitions, magnetic order, and superconductivity in a more accurate and predictive manner. Both materials-specific calculations on real materials and the study of simplified models will be conducted. New capabilities will be developed to extend the system sizes that can be treated, further improve accuracy, compute excited state and response properties, and treat spin-orbit coupling.The leading difficulty in computer simulations of interacting many-fermion systems is the sign or phase problem. The constrained path or phase-free auxiliary-field quantum Monte Carlo approach provides a general framework for both ab initio materials simulations (as an approach to go beyond standard density-functional calculations) and for calculations in lattice models of strongly correlated systems. Success in the development can be expected to impact beyond the specific systems being studied. The PI will continue to integrate research with education and outreach activities, by mentoring both undergraduate and graduate students in research, incorporating materials from this project into courses, reaching out to minority students, and fostering interdisciplinary collaboration in computational science education and research. In the larger scientific community, the PI will continue to play an active role in training students, post-docs, and senior researchers through schools and workshops, and develop software packages and tutorials for hands-on learning of new theoretical and computational approaches and the properties of strongly interacting electron systems.