Electronic Structure Calculations of Materials by Auxiliary-Field Quantum Monte Carlo

PI和合作者开发了一种量子场量子蒙特卡罗（QMC）方法，该方法具有提高材料电子结构计算能力的前景。PI建议将新方法应用于材料特定的问题，并继续其发展。该项目旨在：（i）固体基态的精确计算，（ii）分子和固体中几何和结构优化的广义力的计算，（iii）激发态性质的计算及其在原型半导体中的应用，以及（iv）强相关材料的从头算和模型计算。理解和预测材料特性需要在最基本的层面上进行稳健可靠的计算。通常，所需的效应源于电子相关性，处理过程中的微小误差可能导致性质的关键和定性差异。尽管他们取得了巨大的成功，基于密度泛函理论的标准计算电子结构方法并不总是足够的。特别是在强相关材料中，这是特别重要的理论和技术，他们有时会导致定性不正确的结果。 QMC方法允许通过随机采样进行多体计算，是处理相关材料的一种有前途的选择。然而，它们的能力的限制，迄今为止，阻止了更广泛的应用QMC的许多问题，精确计算的电子相关性是迫切需要的。通过利用新的领域框架所带来的机会，PI将解决其中的一些限制。PI过去的经验和正在进行的研究使他能够有效地实施拟议的项目。该研究的成功完成将增强凝聚态第一性原理计算的能力，推动相关材料的研究。此外，所开发的理论框架和技术也将与核物理学、高能物理学和量子化学相关，其中类似的方法用于多体系统中的非微扰计算。在过去的经验和成功的基础上，PI将继续将研究与教育和推广活动相结合，通过指导本科生和研究生的研究，将该项目的材料纳入新课程，接触汉普顿大学（HBCU）的少数民族学生，并促进计算科学教育和校园研究的跨学科合作。在更大的科学界，PI将继续发挥积极作用，通过学校和讲习班培训学生，博士后和高级研究人员，开发软件和教程，用于动手学习新的理论和计算方法。此外，该项目还将通过推进QMC方法以促进其广泛使用，并通过直接代码贡献，为材料建模和模拟的计算机代码的建立做出贡献。

The PI and collaborators have developed an auxiliary-field quantum Monte Carlo (QMC) method that exhibits promising characteristics for improving the capabilities for electronic structure calculations of materials. The PI proposes to apply the new method to materials- specific problems, and continue its development. The project aims for: (i) accurate calculations of the ground state of solids, (ii) computation of generalized forces for geometry and structural optimizations in molecules and solids, (iii) calculations of excited-state properties with applications to prototypical semiconductors, and (iv) both ab initio and modelcalculations of strongly correlated materials.Intellectual merit. Understanding and predicting materials properties requires robust and reliable calculations at the most fundamental level. Often the desired effects originate from electron correlations, and small errors in their treatment can result in crucial and qualitative differences in the properties. Despite their tremendous success, standard computational electronic structure methods based on density functional theory are not always sufficient. Especially in strongly correlated materials, which are of particular theoretical and technological importance, they can sometimes lead to qualitatively incorrect results. QMC methods, which allow many-body calculations by stochastic sampling, are a promising alternative for treating correlated materials. Limitations in their capability, however, have thus far prevented wider applications of QMC to the many problems where accurate computations of electron correlations are critically needed. By exploiting opportunities that the new auxiliary-field framework presents, the PI will address some of these limitations.The PI's past experience and on-going research have ideally positioned him to effectively pursue the proposed project. Successful completion of this research will enhance the capabilities of first-principles computation in condensed matter, and advance the study of correlated materials. Further, the theoretical framework and technologies that are developed will also be relevant to nuclear physics, high-energy physics, and quantum chemistry, where similar approaches are used for non-perturbative calculations in many-body systems.Broader impacts. Building on past experience and success, 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 a new course, reaching out to minority students at Hampton University (HBCU), and fostering interdisciplinary collaboration in computational science education and research on campus. 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, developing software andtutorials for hands-on learning of new theoretical and computational approaches. In addition, the project will contribute to the build-up of computer codes for modeling and simulation of materials, by advancing QMC methodology to enable and facilitate its wide use, and by direct code contribution.***