An open‐source framework for analyzing N‐electron dynamics. I. Multideterminantal wave functions

Abstract

The aim of the present contribution is to provide a framework for analyzing and visualizing the correlated many-electron dynamics of molecular systems, where an explicitly time-dependent electronic wave packet is represented as a linear combination of N -electron wave functions. The central quantity of interest is the electronic flux density, which contains all information about the transient electronic density, the associated phase, and their temporal evolution. It is computed from the associated one-electron operator by reducing the multi-determinantal, many-electron wave packet using the Slater-Condon rules. Here, we introduce a general tool for post-processing multi-determinant configuration-interaction wave functions obtained at various levels of theory. It is tailored to extract directly the data from the output of standard quantum chemistry packages using atom-centered Gaussian-type basis functions. The procedure is implemented in the open-source Python program detCI@ORBKIT, which shares and builds upon the modular design of our recently published post-processing toolbox [J. Comput. Chem. 37 (2016) 1511]. The new procedure is applied to ultrafast charge migration processes in different molecular systems, demonstrating its broad applicability.Convergence of the N -electron dynamics with respect to the electronic structure theory level and basis set size is investigated. This provides an assessment of the robustness of qualitative and quantitative statements that can be made concerning dynamical features observed in charge migration simulations.

Electronic and nuclear flux analysis on nonadiabatic electron transfer reaction: A view from single‐configuration adiabatic born–huang representation

“…. The present dominance of the energy gap | V 1 − V 2 | over the nonadiabatic coupling | u | 2 in determining Ω( t ) seems to be partly in harmony with the recent observation by Pohl et al that the frequency of the charge migration in LiH in their calculations was found to be determined by the energy gap between the adiabatic potentials . However, the multiple configuration in the Born–Huang expansion of the total wavefunction in the present study of LiF has been brought about only by the nonadiabatic coupling itself, since otherwise keeps to be throughout.…”

“…Flux analyses have also been studied for nonadiabatic processes and charge migration dynamics in systems such as HCCl, benzene and LiH . We here present a flux analysis of full quantum mechanical dynamics of a nonadiabatic electron‐transfer process in the system of LiF ↔ Li + F ‐ to attain deeper insights about the break‐down of the Born–Oppenheimer approximation.…”

“…[43] Flux analyses have also been studied for nonadiabatic processes [44] and charge migration dynamics in systems such as HCCl, [45] benzene [46] and LiH. [47] We here present a flux analysis of full quantum mechanical dynamics of a nonadiabatic electron-transfer process in the system of LiF $ Li + Fto attain deeper insights about the break-down of the Born-Oppenheimer approximation. Yonehara and Takatsuka are among the first who performed flux analysis over nonadiabatic electron transfer in NaCl $ Na + Clin terms of nonadiabatic electron wavepacket theory based on mixed quantum (electron) and classical (nuclear) representation.…”

An open‐source framework for analyzing N‐electron dynamics. II. Hybrid density functional theory/configuration interaction methodology

“…The framework det CI@ORBKIT is written in Python, simplifying its portability on different platforms and offering efficient standard libraries for visualization purposes. Implementation details are given elsewhere . The dynamics program is not part of the standard implementation and can be performed using either a user‐written code or, for example, the Matlab WAVEPACKET package .…”

“…Implementation details are given elsewhere. [20] The dynamics program is not part of the standard implementation and can be performed using either a userwritten code or, for example, the Matlab WAVEPACKET package. [30] In the present work, all dynamical simulations were performed using GLOCT, an in-house implementation of a propagator for the reduced-density matrix and related quantities.…”