CAREER: Theoretical and computational methods for spin-forbidden processes in complex systems

内华达大学里诺分校的Sergey Varganov获得了化学学部化学理论、模型和计算方法项目的奖励，为研究涉及电子自旋变化的化学反应开发了新的理论和计算方法。（电子可以被认为是微小的旋转陀螺，但实际上“电子自旋”是一种纯粹的量子力学性质，没有经典物理类比。）这种被称为“禁止自旋”的反应在化学、物理和生物学的不同领域都很重要。Varganov和他的研究小组专注于两种类型的方法：一种适用于小分子的高度精确的方法和一种专为非常大的生物分子设计的简单统计方法。他们正在使用这些方法来了解自旋禁止反应的基本特性，以及电子自旋在复杂生物分子中的作用，这些分子能够加速工业上重要的反应，如氢还原和氧化。这些研究促进了用于不同能源应用的新型先进材料的开发。Varganov教授还在开发示范和计算工具，以加强化学教学和外联活动的影响。这些工具包括代表化学反应能量格局的3d打印模型，以及适用于研究生和本科生化学课程的简化版计算化学方法。该项目旨在发展最先进的理论和计算方法，以研究复杂系统中自旋禁止过程的动力学和动力学，包括系统间交叉、自旋交叉和自旋禁止反应。重点介绍了新的非绝热统计理论和高效的多卵分子动力学方法。通过在碎片分子轨道方法中实现新的算法，使统计理论适用于具有数千个原子的系统中的自旋禁止过程。多卵分子动力学为自旋禁止动力学计算中的动力学效应提供了一种通用的方法。新方法在小分子上得到了验证，并用于研究金属酶[NiFe]-氢化酶和镍取代红霉素的催化氢氧化/还原。教育部分集中在使用简单化学反应的3d打印势能表面的分子动力学演示。

Sergey Varganov of the University of Nevada, Reno is supported by an award from the Chemical Theory, Models, and Computational Methods program in the Chemistry Division to develop new theoretical and computational methods for studying chemical reactions involving a change of electron spin. (Electrons can be thought of as tiny spinning tops, but in reality "electron spin" is a purely quantum mechanical property that has no classical physical analogue.) Such reactions, referred to as "spin-forbidden", are important in different areas of chemistry, physics and biology. Varganov and his research group focus on two types of methods: a highly accurate approach applicable to small molecules and a simple statistical approach designed for very large biological molecules. They are using these methods to understand the fundamental properties of spin-forbidden reactions and the role of electron spin in complex biological molecules capable of accelerating industrially important reactions, such as hydrogen reduction and oxidation. These studies are facilitating development of new advanced materials for different energy applications. Prof. Varganov is also developing demonstration and computational tools to enhance the teaching of chemistry and the impact of outreach activities. These tools include 3D-printed models representing energy landscapes of chemical reactions and simplified versions of computational chemistry methods suitable for use in graduate and undergraduate chemistry courses. This project is aimed at developing state of the art theoretical and computational methods to investigate the kinetics and dynamics of spin-forbidden processes, including intersystem crossings, spin crossovers and spin-forbidden reactions, in complex systems. The focus is on the novel nonadiabatic statistical theory and efficient multiple spawning molecular dynamics methods. The statistical theory is made applicable to spin-forbidden processes in systems with thousands of atoms by implementing new algorithms within the fragment molecular orbital method. The multiple spawning molecular dynamics provides a general approach to account for dynamic effects in the spin-forbidden kinetics calculations. The new methods are validated on small molecules and used to investigate catalytic hydrogen oxidation/reduction on the metalloenzymes [NiFe]-hydrogenase and Ni-substituted rubredoxin. The education component is centered on the molecular dynamics demonstrations using 3D-printed potential energy surfaces of simple chemical reactions.