Ab Initio Downfolding Approach to Exciton-Continuum

激子连续体从头算向下折叠方法

基本信息

批准号：
2114081
负责人：
Diana Qiu
金额：
$ 37.46万
依托单位：
Yale University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-07-01 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2114081&HistoricalAwards=false
关键词：
Ab Initio Downfolding Approach Exciton

项目摘要

NONTECHNICAL SUMMARYThis award supports research, education, and outreach activities focused on understanding excitations created by the absorption of light in materials. Understanding these excitations is of fundamental importance to a wide range of processes that rely on light absorption, including light harvesting by solar cells, photosynthesis in plants, and chemical reactions catalyzed by light. In all these processes, the absorption of light creates excitons, which are excited states composed of a negatively charged electron and a positively charged hole bound together by the Coulomb interaction. It is possible to calculate the energy levels and character of these excitons, and consequently, the energy and amount of light that can be absorbed by a material, but currently, accurate calculations of this nature are limited to systems with only tens of atoms and excitations over a small energy range due to the computational cost of the calculation. This project aims to develop, implement and apply new computational techniques that will allow for the calculation of much larger systems containing up to thousands of atoms and with energies spanning the electromagnetic spectrum from the infrared to x-ray ranges. The main idea is to divide the largescale system into smaller subsystems. As long as excitons can be well-approximated as being confined to a single subsystem, then each subsystem can be calculated separately, which dramatically reduces the computational cost. The effect of interactions between the subsystems is approximated by changing the strength of interactions inside each subsystem, which in turn reveals how scattering between subsystems can influence the exciton energies and lifetimes. This method will be applied to study x-ray absorption spectra and molecules adsorbed on the surface of bulk materials. This project will enhance understanding of excitons at higher energy and faster timescales, and pave the way for the development of improved devices for light harvesting and molecular sensing.This project supports the education of a graduate student. Additionally, this project will integrate research, education, and mentoring with a scaffolded outreach program designed to broaden the participation of groups that are historically underrepresented in science and engineering. The PI will give public lectures, develop a summer materials science workshop, and offer a yearly undergraduate summer internship for students from the New Haven public school system. The proposed outreach includes a rigorous data collection component that will allow the impact of the program to be assessed.TECHNICAL SUMMARYThis award supports research, education, and outreach activities focused on understanding exciton dynamics and scattering between subspaces in nanostructured and heterogeneous systems. Currently, ab initio calculations of excitons within many-body perturbation theory (MBPT) are limited by their considerable computational cost to static calculations on small systems with tens of atoms and energy ranges of less than 10 eV, leaving many systems of current physical interest, such as heterostructures, defects, and complex nanostructures, beyond the reach of conventional calculations. This project aims to develop, implement and apply an ab initio formalism within MBPT that describes the dynamical interactions between excitons in different physical subsystems, defined by energy scales or spatial localization. The objective is to extend the current capabilities of these computational techniques to study light-matter interactions in larger, more complex systems and over energy scales of hundreds to thousands of eV. This project concurrently develops new techniques to include dynamical and lifetime effects due to coupling between physical subsystems in calculations of exciton spectra.The proposed methods are based on an extension of the GW plus Bethe Salpeter equation (GW-BSE) formalism. Instead of truncating the Hilbert space, as is done in conventional calculations, the coupling of a physical subsystem to a larger Hilbert space will be accounted for through a matrix downfolding approach that includes the dynamics of the coupling. The developed methods will be applied to the computation of spectra and lifetimes associated with excitons in x-ray absorption spectroscopy of two-dimensional layered van der Waals materials, oxides, and amorphous systems. The developed methods will also be applied to study excitonic energy transfer across heterointerfaces between molecules and two-dimensional materials. This project supports the education of a graduate student. Additionally, this project will integrate research, education, and mentoring with a scaffolded outreach program designed to broaden the participation of groups that are historically underrepresented in science and engineering. The PI will give public lectures, develop a summer materials science workshop, and offer a yearly undergraduate summer internship for students from the New Haven public school system. The proposed outreach includes a rigorous data collection component that will allow the impact of the program to be assessed.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.

非技术摘要该奖项支持研究、教育和推广活动，重点是了解材料吸收光所产生的激发。了解这些激发对于依赖光吸收的各种过程至关重要，包括太阳能电池的光收集、植物的光合作用以及光催化的化学反应。在所有这些过程中，光的吸收会产生激子，激子是由带负电的电子和带正电的空穴通过库仑相互作用结合在一起组成的激发态。可以计算这些激子的能级和特征，从而计算材料可以吸收的光的能量和数量，但目前，这种性质的精确计算仅限于只有数十个原子和激发的系统由于计算的计算成本，在较小的能量范围内。该项目旨在开发、实施和应用新的计算技术，这些技术将允许计算包含多达数千个原子且能量跨越从红外到 X 射线范围的电磁频谱的更大系统。其主要思想是将大型系统划分为较小的子系统。只要激子可以很好地近似为限制在单个子系统中，那么每个子系统都可以单独计算，这大大降低了计算成本。通过改变每个子系统内部相互作用的强度来近似子系统之间相互作用的影响，这反过来又揭示了子系统之间的散射如何影响激子能量和寿命。该方法将应用于研究X射线吸收光谱和吸附在块体材料表面的分子。该项目将增强对更高能量和更快时间尺度的激子的理解，并为开发用于光捕获和分子传感的改进设备铺平道路。该项目支持研究生的教育。此外，该项目还将研究、教育和指导与支架式外展计划相结合，旨在扩大历史上在科学和工程领域代表性不足的群体的参与。 PI 将举办公开讲座，举办夏季材料科学研讨会，并为纽黑文公立学校系统的学生提供每年一次的本科生暑期实习机会。拟议的推广活动包括严格的数据收集部分，以便评估该计划的影响。技术摘要该奖项支持研究、教育和推广活动，重点是了解纳米结构和异质系统中的激子动力学和子空间之间的散射。目前，多体微扰理论 (MBPT) 中激子的从头计算受到其相当大的计算成本的限制，无法在具有数十个原子且能量范围小于 10 eV 的小型系统上进行静态计算，从而使许多系统成为当前物理感兴趣的系统，例如异质结构、缺陷和复杂的纳米结构，超出了传统计算的范围。该项目旨在开发、实施和应用 MBPT 中的从头开始形式主义，该形式主义描述了不同物理子系统中激子之间的动态相互作用，由能量尺度或空间定位定义。目标是扩展这些计算技术的当前能力，以研究更大、更复杂的系统以及数百至数千电子伏特能量尺度上的光与物质相互作用。该项目同时开发新技术，以包括由于激子谱计算中物理子系统之间的耦合而产生的动力学和寿命效应。所提出的方法基于 GW 加 Bethe Salpeter 方程 (GW-BSE) 形式主义的扩展。与传统计算中所做的截断希尔伯特空间不同，物理子系统与更大希尔伯特空间的耦合将通过包含耦合动力学的矩阵下折叠方法来解释。所开发的方法将应用于二维层状范德华材料、氧化物和非晶系统的X射线吸收光谱中与激子相关的光谱和寿命的计算。所开发的方法还将应用于研究分子和二维材料之间异质界面的激子能量转移。该项目支持研究生的教育。此外，该项目还将研究、教育和指导与支架式外展计划相结合，旨在扩大历史上在科学和工程领域代表性不足的群体的参与。 PI 将举办公开讲座，举办夏季材料科学研讨会，并为纽黑文公立学校系统的学生提供每年一次的本科生暑期实习机会。拟议的外展活动包括严格的数据收集部分，以便评估该计划的影响。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。