Ab initio description of optical nonlinearities induced by impulsive broadband radiation (INPULS)

分子中光限幅(OL)的理论描述仍处于起步阶段，尽管第一性原理方法在表征这些体系的光谱性质方面获得了广泛的应用。已建立的基于模型哈密顿的方法已被证明是非常有效地再现实验趋势。然而，它们对经验参数的依赖极大地限制了它们对未知化合物的适用性。申请人和她的同事于2014年首次提出了基于实时依赖于时间的密度泛函理论(RT-TDDFT)的OL从头算方案，为以负担得起的计算成本对这一现象进行非微扰、无参数描述铺平了道路。然而，促成OL的机制的多样性和复杂性要求进行专门的分析和进一步的发展，这是本项目的核心。在这里，我们的目标是开发一种基于RT-TDDFT的高效和准确的第一性原理方案来预测、描述和解释有机分子中的OL和相关的光学非线性。我们计划扩展我们的SEED方法，以(I)确定OL的驱动机制；(Ii)考虑电子-振动相互作用的影响；(Iii)在方法中包括与环境的静电耦合。与外部项目合作伙伴进行的实验的直接比较被视为我们结果的定量参考点。将开发的方法纳入自动化工作流程将使其传播也超越理论界。

The theoretical description of optical limiting (OL) in molecules is still in its infancy, despite the popularity gained by first-principles methods in the characterization of spectroscopic properties in these systems. Established methods based on model Hamiltonians have proven to be very effective to reproduce experimental trends. However, their dependence on empirical parameters limits dramatically their applicability to unknown compounds. The first development of an ab initio scheme for OL based on real-time time-dependent density-functional theory (RT-TDDFT), proposed by the applicant and her coworkers in 2014, has paved the way to a non-perturbative, parameter-free description of this phenomenon at affordable computational costs. However, the variety and complexity of the mechanisms contributing to OL call for dedicated analysis and further developments which are at the core of this project. Herein, we aim to develop an efficient and accurate first-principles scheme based on RT-TDDFT to predict, describe, and interpret OL and related optical nonlinearities in organic molecules. We plan to extend our seed approach to (i) identify the driving mechanisms of OL; (ii) account for the effects of electron-vibrational interactions; (iii) include in the method electrostatic coupling with the environment. Direct comparison with experiments performed by an external project partner is envisioned as a quantitative point of reference for our results. The inclusion of the developed method into an automated workflow will enable its dissemination also beyond the theorists’ community.