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

内华达大学雷诺分校的谢尔盖·瓦尔加诺夫得到了化学部化学理论、模型和计算方法计划的支持，以开发新的理论和计算方法来研究涉及电子自旋变化的化学反应。(电子可以被认为是微小的旋转顶端，但实际上，“电子自旋”是一种纯粹的量子力学性质，没有经典的物理类比。)这种被称为“自旋禁忌”的反应在化学、物理和生物学的不同领域都很重要。瓦尔加诺夫和他的研究小组专注于两种方法：一种适用于小分子的高精度方法，另一种是针对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性质，以及电子自旋在能够加速重要工业反应的复杂生物分子中的作用，如氢还原和氧化。这些研究正在促进用于不同能源应用的新型先进材料的开发。瓦尔加诺夫教授还在开发演示和计算工具，以加强化学教学和推广活动的影响。这些工具包括代表化学反应能量景观的3D打印模型，以及适合在研究生和本科生化学课程中使用的计算化学方法的简化版本。这个项目的目的是发展最先进的理论和计算方法来研究复杂系统中自旋禁忌过程的动力学和动力学，包括系间交叉、自旋交叉和自旋禁忌反应。重点介绍了新的非绝热统计理论和高效的多重产卵分子动力学方法。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的自旋禁忌过程。多重产卵分子动力学提供了一种在自旋禁忌动力学计算中解释动力学效应的一般方法。新方法在小分子上得到验证，并用于金属酶[NiFe]-氢酶和镍取代的Rubredox的催化氢氧化/还原反应。教学部分以分子动力学演示为中心，使用3D打印的简单化学反应的势能面。

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.