Song Huajing, Freixas Victor M, Fernandez-Alberti Sebastian, White Alexander J, Zhang Yu, Mukamel Shaul, Govind Niranjan, Tretiak Sergei
Physics and Chemistry of Materials, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
Departamento de Ciencia y Tecnologia, Universidad Nacional de Quilmes/CONICET, B1876BXD, Bernal, Argentina.
J Chem Theory Comput. 2021 Jun 8;17(6):3629-3643. doi: 10.1021/acs.jctc.1c00131. Epub 2021 May 20.
The recently developed ab initio multiple cloning (AIMC) approach based on the multiconfigurational Ehrenfest (MCE) method provides a powerful and accurate way of describing the excited-state dynamics of molecular systems. The AIMC method is a controlled approximation to nonadiabatic dynamics with a particular strength in the proper description of decoherence effects because of the branching of vibrational wavepackets at a level crossing. Here, we report a new implementation of the AIMC algorithm in the open source NWChem computational chemistry program. The framework combines linear-response time-dependent density functional theory with Ehrenfest mean-field theory to determine the equations of motion for classical trajectories. The multidimensional wave function is decomposed into a superposition of Gaussian coherent states guided by Ehrenfest trajectories (i.e., MCE approach), which can clone with fully quantum mechanical amplitudes and phases. By using an efficient time-derivative based nonadiabatic coupling approach within the AIMC method, all observables are calculated on-the-fly in the nonadiabatic molecular dynamics process. As a representative example, we apply our implementation to study the ultrafast photoinduced electronic and vibrational energy transfer in a pyridine molecule. The effects of the cloning procedure on electronic and vibrational coherence, relaxation and unidirectional energy transfer are discussed. This new AIMC implementation provides a high-level nonadiabatic molecular dynamics framework for simulating photoexcited dynamics in complex molecular systems and experimentally relevant ultrafast spectroscopic probes, such as nonlinear coherent optical and X-ray signals.
最近基于多组态埃伦费斯特（MCE）方法开发的从头算多克隆（AIMC）方法，为描述分子体系的激发态动力学提供了一种强大而精确的方式。AIMC方法是对非绝热动力学的一种可控近似，由于振动波包在能级交叉处的分支，它在正确描述退相干效应方面具有独特优势。在此，我们报告了AIMC算法在开源计算化学程序NWChem中的一种新实现。该框架将线性响应含时密度泛函理论与埃伦费斯特平均场理论相结合，以确定经典轨迹的运动方程。多维波函数被分解为由埃伦费斯特轨迹引导的高斯相干态的叠加（即MCE方法），其可以用完全量子力学的振幅和相位进行克隆。通过在AIMC方法中使用基于有效时间导数的非绝热耦合方法，在非绝热分子动力学过程中实时计算所有可观测量。作为一个代表性例子，我们将我们的实现应用于研究吡啶分子中的超快光致电子和振动能量转移。讨论了克隆过程对电子和振动相干性、弛豫以及单向能量转移的影响。这种新的AIMC实现为模拟复杂分子体系中的光激发动力学以及实验相关的超快光谱探针（如非线性相干光学和X射线信号）提供了一个高级非绝热分子动力学框架。
