CAREER: Enabling the Accurate Simulation of Multi-Dimensional Core-Level Spectroscopies in Molecular Complexes using Time-Dependent Density Functional Theory

在化学系化学理论、模型和计算方法(CTMC)计划的支持下，孟菲斯大学的Daniel Nascimento博士正在开发模拟分子与X射线相互作用的计算方法。这些模拟提供了关于分子行为的有价值的信息，进而提供了在与医学、材料科学、工程和环境化学相关的技术应用中如何使用和操纵分子的宝贵信息。纳西门托博士和他的研究小组将开发具有成本效益的算法来模拟多维X射线光谱分析，这将使人们更好地了解与新材料和技术开发相关的分子系统。这些算法将作为PSI4电子结构软件包的一部分实施，PSI4电子结构软件包是一个开源的、最先进的量子化学软件包，可免费向化学界提供。作为推广和教育工作的一部分，纳西门托博士将启动一个面向中南部地区本科生的计算化学暑期项目。这些努力旨在影响未来理论和计算化学人员的招聘和发展，并被视为努力为该领域建立多样化、有才华的未来劳动力的工具。X射线自由电子激光(XFEL)技术的最新进展为在高能下进行多维核心能级光谱实验开辟了新的途径。然而，为了有效地解释和理解这些设施产生的海量数据，必须有准确的理论模型，能够忠实地复制潜在的过程。目前用于解释实验X射线数据的模型要么过于简化，无法预测，要么需要大量的计算，而这些计算只适用于相对较小的分子。纳西门托博士和他的研究小组正在采取一种新的方法，利用响应理论的原理来开发、实施和应用具有成本效益的算法，以模拟真实世界系统中的多维核心能级光谱，这些系统具有大约100到150个原子。这些算法将被集成到PSI4电子结构包中。通过这项研究，纳西门托博士旨在加深我们对几个关键方面的理解，包括二阶松弛效应在计算分子络合物中激发态跃迁矩中的重要性，利用准简并微扰理论在这些跃迁矩中引入自旋-轨道耦合效应，以及发展一种特定于状态的策略，以最小的参数处理耗散通道。由该项目产生的算法和计算机程序有望增强多维X射线光谱模拟的执行方式，并在XFEL驱动的科学的新时代增加计算化学的覆盖范围和预测能力。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Theory, Models and Computational Methods (CTMC) program in the Division of Chemistry, Dr. Daniel Nascimento of the University of Memphis is developing computational approaches to simulate how molecules interact with X-rays. These simulations provide valuable information on how molecules behave, and by extension, how they can be used and manipulated in technological applications relevant to medicine, materials science, engineering, and environmental chemistry. Dr. Nascimento and his research group will develop cost-effective algorithms to simulate multi-dimensional X-ray spectroscopies that will enable a better understanding of molecular systems relevant for the development of novel materials and technologies. These algorithms will be implemented as part of the Psi4 electronic structure package, an open-source, state-of-the-art quantum chemistry software package freely available to the chemistry community. As part of outreach and educational efforts, Dr. Nascimento will launch a summer program in computational chemistry targeting undergraduate students from across the Mid-South region. These efforts are designed to impact the recruitment and development of future theoretical and computational chemists and are seen as a vehicle to work toward building a diverse, talented future workforce for the field.Recent advancements in X-ray free-electron laser (XFEL) technologies have opened up new avenues for conducting multi-dimensional core-level spectroscopy experiments at high energies. However, to effectively interpret and make sense of the vast amount of data generated by these facilities, it is imperative to have precise theoretical models that can faithfully replicate the underlying processes. Current models employed in the interpretation of experimental X-ray data are either too simplified to be predictive or entail extensive computations that are practical only for relatively small molecules. Dr. Nascimento and his research group are taking a novel approach by harnessing the principles of response theory to develop, implement, and apply cost-effective algorithms for simulating multi-dimensional core-level spectroscopies in real-world systems, featuring around 100 to 150 atoms. These algorithms will be integrated into the Psi4 electronic structure package. Through this research effort, Dr. Nascimento aims to deepen our understanding of several critical aspects, including the significance of second-order relaxation effects in calculating excited-state transition moments in molecular complexes, the utilization of quasi-degenerate perturbation theory to introduce spin-orbit coupling effects into these transition moments, and the development of a state-specific strategy for addressing dissipation channels with minimal parameterization. The algorithms and computer programs resulting from this project are expected to enhance the ways in which multi-dimensional X-ray spectroscopy simulations are performed and to increase the reach and predictive ability of computational chemistry in the new era of XFEL-driven science.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.