Time-Domain Atomistic Theory and Simulation of Excitation Dynamics on the Nanoscale

南加州大学的Oleg V. Prezhdo获得了化学系化学理论、模型和计算方法项目的奖励，以开发研究纳米级材料的计算方法。该奖项由材料研究部凝聚态物质和材料理论项目共同资助。在纳米尺度上研究物质可以让科学家和工程师开发出更小更快的电子和电光设备。这些设备在技术上有很多好处。例如，它们可以提高太阳能电池的效率并降低成本。许多新技术，如与量子信息科学相关的技术，也来自纳米尺度的研究。纳米材料弥合了分子尺度和体尺度之间的差距，呈现出新的现象。要理解这些现象，需要原子水平的描述和精细的时间分辨率。为了获得这种详细的理解，Prezhdo教授和他的研究小组开发了新的理论方法，并使用它们来研究纳米材料的超快动力学。这项理论研究是在实验人员的密切合作下进行的。Prezhdo小组目前的重点是混合有机/无机钙钛矿，它显示出创纪录的太阳能电池效率，以及二维材料，如金属二硫族化合物和黑磷，这可以导致只有几个原子厚度的设备的发展。Prezhdo教授致力于课程开发，旨在提高学生对能源科学的参与。这些研究植根于非绝热（NA）和半经典分子动力学（MD）的最新进展，以及它们在时域密度泛函理论（TDDFT）中的实现。重点是对最近在纳米材料上进行的时间解决实验中提出的基本问题的调查。特别关注NAMD的新模拟方法和算法的开发和测试，重点是严密性，准确性，效率和对大型系统的适用性，这些系统经历了涉及激发态和超快时间尺度的实际重要非平衡过程。在TDDFT中实现和测试NAMD方法，目的是将NAMD的适用性扩展到新的问题和更大的系统，这也是本研究的目标。更大的系统的电子结构可以用从头算和紧密结合DFT来描述，包括一系列新的NAMD技术（Liouville空间NAMD）和过程类型（多粒子和自旋轨道相互作用）。最后，对二维材料和卤化物钙钛矿的激发动力学进行了研究。这些材料在光伏、光催化、电子、自旋电子、等离子体、谷电子和相关技术方面具有很大的前景，是未来能量收集和信息处理方面社会进步的基础。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。

Oleg V. Prezhdo of the University of Southern California is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop computational approaches to study nanoscale materials. The award is cofunded by the Condensed Matter and Materials Theory program in the Division of Materials Research. Studying matter at the nanoscale allows scientists and engineers to develop smaller and faster electronic and electro-optic devices. These devices have many technological benefits. For example, they can improve the efficiency and lower the cost of solar cells. Many new technologies, such as those relevant to quantum information science also emerge from nanoscale research. Bridging the gap between molecular and bulk scales, nanoscale materials exhibit novel phenomena. An atom-level description and fine time-resolution are needed to understand these phenomena. To gain this detailed understanding, Professor Prezhdo and his research group develop novel theoretical methods and use them to study ultrafast dynamics in nanomaterials. This theoretical research is performed in close collaboration with experimentalists. The current focus of the Prezhdo group is on hybrid organic/inorganic perovskites, which show record solar cell efficiencies, as well as on two-dimensional materials, such as metal dichalcogenides and black phosphorus, which can lead to the development of devices that are just a few atoms in thickness. Professor Prezhdo is engaged at curriculum development aimed at increasing student involvement in energy sciences.These studies are rooted in the recent advances in nonadiabatic (NA) and semi-classical molecular dynamics (MD), and their implementation within time-domain density functional theory (TDDFT). The focus is on the investigation of the fundamental questions posed in the recent time resolved experiments performed on nanoscale materials. Specific attention is given to the development and testing of new simulation approaches and algorithms for NAMD with focus on rigor, accuracy, efficiency and applicability to large systems, which undergo practically important non-equilibrium processes involving excited electronic states and ultrafast timescales. The implementation and testing of the NAMD approaches within TDDFT with the goal of extending the applicability of NAMD to new problems and larger systems is also a goal of this research. The larger systems have electronic structure can be described by ab initio and tight binding DFT, including a new family of NAMD techniques (Liouville space NAMD) and types of processes (many-particle and spin-orbit interactions). Finally, the study of the excitation dynamics in two-dimensional materials and halide perovskites, which are under intense experimental investigation are investigated. These materials carry great promise for photovoltaic, photocatalytic, electronic, spintronic, plasmonic, valleytronic and related technologies, underlying future societal advances in energy harvesting and information processes.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.