NSF/DMR-BSF: Density Functionals for Predictive Excited-State Calculations of Solids (NSF-BSF Application)

该奖项支持理论和计算研究以及教育，以推进从基本科学原理预测材料性质的计算方法。光电子应用新材料的发现和开发受到对材料如何收获光、转导能量和传输电荷的详细了解的极大限制-所有涉及电子激发态的现象，其中电子的配置导致比材料的最低或基态能量更高的能量。现有的计算方法可以预测这些过程，但它们需要大量的计算成本，而具有类似精度的替代方法将能够预测日益复杂的材料，并将这些方法用于材料的发现和设计。该研究项目为开发更有效的预测理论框架奠定了重要的基础，这些理论框架与实际材料中电子激发态的计算成本更高的现有方法相辅相成。这项工作的核心是指导所有年龄段的下一代计算材料理论家，重点是积极招募和提升女性和其他少数族裔本科生和研究生；并为湾区及其他地区的本科生、小学生、中学生以及教育工作者参观当地的研究设施。该奖项支持理论和计算研究，以及推进预测材料性能的计算方法的教育。电子能带结构是晶体物质的基本性质。它是理解块状材料电荷输运性质的基础。此外，它是理解材料的光学性质和使光谱测量结果合理化的先决条件。在材料和凝聚态物理中，长期以来选择多体微扰理论（MBPT）作为定量确定能带结构的形式。这种形式已经为许多不同类别的金属、半导体和绝缘体提供了出色的电子结构预测。然而，这些预测需要大量的计算成本，而基于从Kohn-Sham方程解中获得的单电子能量和轨道，从密度泛函理论（DFT）中提取能带结构的能力可以减轻这一成本。该项目涉及两国理论和计算合作，通过将最佳调谐范围分离杂化（OTRSH）密度泛函与多体摄动理论相结合，为准粒子带隙、带结构和复杂固态材料的光学光谱的第一级原理计算预测开发一个强大的框架，比现有方法具有更高的精度和效率。pi的工作表明，OTRSH功能导致了广泛类别的分子晶体和一组IV族和III-V族半导体和绝缘体的能带结构和光谱，具有领先的从头算GW和GW- bse方法的精度。在此，ppi在此成功的基础上，同时推进了两个重要领域。首先，pi将评估OTRSH作为固体GW和GW- bse计算的有效起点。其次，在先前工作的基础上，pi将探索在没有GW计算的情况下确定准确的DFT-OTRSH波段结构和TDDFT-OTRSH光学特性的路线。一旦验证，pi将使用OTRSH起点计算一系列复杂材料的准粒子间隙和能带结构，以及线性吸收光谱，包括卤化物钙钛矿，这些重要的光电材料，标准GW和GW- bse方法已被证明是不充分或不一致的。到目前为止，OTRSH在固体能带结构和光谱方面取得的进展令人鼓舞，因为它表明，通常有可能将一个参数固定为取向平均介电常数，然后调整单个参数-距离分离参数-以产生与GW-BSE一致的能带结构和光谱，部分或完全减少与MBPT相关的计算成本。考虑到单一参数的OTRSH波段结构的质量，OTRSH是否可以作为复杂结构和化学非均相体系的GW和GW- bse计算的最佳起点？此外，能否独立于GW-BSE的计算和实验设置这一单一参数还有待观察。对于各向同性和各向异性材料，它能否以一种计算上易于处理的方式从材料性质中预测出来？该项目的目的是解决这些问题，并最终开发有效的方法来理解现有的和预测复杂材料中的新激发态现象。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research, and education to advance computational methods for predicting the properties of materials from fundamental scientific principles. The discovery and development of new materials for optoelectronic applications is significantly limited by a detailed understanding of how materials harvest light, transduce energy, and transport charge - all phenomena involving electronic excited states where the configuration of electrons leads to a higher energy than the lowest or ground state energy of the material. Existing computational methods are predictive for such processes, but they come at significant computational cost, and alternative approaches with similar accuracy would enable predictions for increasingly complex materials and for adapting such methods for materials discovery and design. This research project lays important groundwork toward the development of more efficient predictive theoretical frameworks that are complimentary to more computationally costly existing methods for electronic excited states in real materials. Central to this effort is mentoring of next-generation computational materials theorists at all age levels, with focus on active recruitment and promotion of women and other underrepresented-minority undergraduate and graduate students; and outreach through tours of local research facilities for undergraduate, elementary, and middle-school students – as well as educators – in the Bay area and beyond.TECHNICAL SUMMARYThis award supports theoretical and computational research, and education to advance computational methods for predicting the properties of materials. The electronic band structure is a fundamental property of crystalline matter. It serves as the basis for understanding charge transport properties of bulk materials. Moreover, it is a prerequisite for understanding optical properties of materials and for rationalizing the results of spectroscopic measurements. In materials and condensed matter physics, the formalism of choice for quantitative determination of the band structure has long been many-body perturbation theory (MBPT). This formalism has yielded excellent electronic structure predictions for many different classes of metals, semiconductors, and insulators. However, these predictions come at significant computational cost, and the ability to extract band structures from density functional theory (DFT), based on the single-electron energies and orbitals obtained from the solution of the Kohn-Sham equation, could alleviate this cost. This project involves a binational theoretical and computational collaboration to develop a robust framework for the first principles computational prediction of the quasiparticle band gaps, band structures, and optical spectra of complex solid-state materials with greater accuracy and efficiency than existing methodologies, by combining optimally-tuned range separated hybrid (OTRSH) density functionals with many-body perturbation theory. The PIs’ work has shown that OTRSH functionals lead to band structures and optical spectra for a broad class of molecular crystals and a set of group IV and III–V semiconductors and insulators, with the accuracy of leading-edge ab initio GW and GW-BSE approaches. Here, the PIs build on this success by advancing two important fronts simultaneously. First, the PIs will evaluate OTRSH as an effective starting point for GW and GW-BSE calculations for solids. Second, building on prior work, the PIs will explore routes to determine accurate DFT-OTRSH band structure and TDDFT-OTRSH optical properties without GW calculations. Once validated, the PIs will use OTRSH starting points to calculate the quasiparticle gap and band structure, as well as the linear absorption spectra, of an array of complex materials, including halide perovskites, important optoelectronic materials for which standard GW and GW-BSE methods have been demonstrated to be inadequate or inconsistent.The progress made thus far with OTRSH for band structure and optical spectra of solids is encouraging, as it suggests that it is in general possible to fix one parameter to the orientationally-averaged dielectric constant and then tune a single parameter – the range-separation parameter – to yield band structures and optical spectra in agreement with GW-BSE, partially or fully mitigating computational costs associated with MBPT. Given the quality of the OTRSH band structure with a single parameter, could OTRSH be an optimal starting point for GW and GW-BSE calculations of complex structurally and chemically heterogeneous systems? Additionally, it remains to be seen whether one can set this single parameter independent of GW-BSE calculations and experiment. Can it be predicted from materials properties in a computationally tractable manner, for isotropic and anisotropic materials alike? The aim of this project is to address these questions, and ultimately develop efficient approaches for understanding existing and predicting new excited-state phenomena in complex materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.