Exact Factorization of the Electron-nuclear Problem and Density Functional Theory Beyond Born-Oppenheimer Approximation
报告题目：Exact Factorization of the Electron-nuclear Problem and Density Functional Theory Beyond
Born-Oppenheimer Approximation
报 告 人：李晨（副教授）
报告日期：2025年8月14日 星期四
报告时间：上午10:00-11:00
报告地点：激光光谱研究所319会议室
报告简介：
In the first part of my talk, I will discuss our recent application of the exact factorization equations for electron-nuclear time-dependent problems. Starting from the exact nuclear Schrödinger equation, we derive inter-subsystem Ehrenfest identities characterizing the energy, momentum, and angular momentum transfer between electrons and nuclei. An effective electromagnetic force operator induced by the electromagnetic field corresponding to the effective scalar and vector potentials appears in all three identities. The effective magnetic field has two components that can be identified with the Berry curvature calculated with (A) different cartesian coordinates of the same nucleus and (B) arbitrary cartesian coordinates of two different nuclei. (A) has a classical interpretation as the induced magnetic field felt by the nucleus, while (B) has no classical analog. Through a case study of a two-state vibronic coupling model with a conical intersection in two dimensions, we show that one can understand the nuclear dynamics particularly for the molecular geometric phase effects in three equally valid perspectives: (i) destructive interference of the branching nuclear wave packet owing to the geometric phase; (ii) an energy-driven effect characterized by the dynamically generated spikes and barrier on the time-dependent potential energy surface; (iii) an effective force field that pushes the nuclear wave density away from the interference region. Particularly, the third perspective provides us new insight into the geometric phase effects and is potentially a new starting point for molecular dynamics simulations. In the second part of my talk, I will discuss density functional theory and approximations beyond the Born-Oppenheimer approximation. Based on the exact factorization framework, we introduce the marginal nuclear wave density and the conditional electronic density as basic variables. We show that an additional electron-nuclear coupling term arises in the Kohn-Sham equations, which couples these equations for different nuclear configurations. This leads to sizable change of electronic density in the nonadiabatic region.
报告人简介：
Chen Li is an assistant professor at the College of Chemistry and Molecular Engineering, Peking University. He received his bachelor’s degree in chemistry and math from Peking University in 2011. After that, he pursued his PhD study in density functional theory at Duke University under the supervision of Prof. Weitao Yang, and obtained his Ph. D. degree in 2016. In 2017, he joined the Max Planck Institute of Microstructure Physics in Germany as a postdoc research scientist and worked with Prof. Hardy Gross on the topic of time dependent density functional theory beyond Born-Oppenheimer approximation. In 2019, he followed Prof. Gross and moved to the Fritz Haber Center for Molecular Dynamics at Hebrew University of Jerusalem in Israel. In September 2020, He finished his postdoc and joined the chemistry department of Peking University as an assistant professor. Prof. Li is engaged in developing novel electronic structure theory methods, including density functional approximations, and wave function theory based on recently developed technique for solving Schrödinger equations. He is also interested in developing time dependent density functional theory beyond the Born-Oppenheimer approximation for capturing nonadiabatic effects.
