RhoDyn: a $\rho$-TD-RASCI framework to study ultrafast electron dynamics in molecules

TL;DR

RhoDyn is a new computational module within OpenMolcas that enables detailed simulations of ultrafast electron dynamics in molecules, incorporating effects like spin-orbit coupling, nuclear vibrations, and ionization.

Contribution

It introduces the RhoDyn module implementing the $ ho$-TD-RASCI formalism for advanced electron dynamics simulations in molecules.

Findings

Successfully simulated L$_{2,3}$ absorption spectra of titanium complex

Modeled high harmonic generation in hydrogen molecule

Analyzed ultrafast charge migration and spin-flip dynamics

Abstract

This article presents the program module \texttt{RhoDyn} as part of the \texttt{OpenMolcas} project intended to study ultrafast electron dynamics within the density-matrix-based time-dependent restricted active space configuration interaction framework ($\rho$-TD-RASCI). The formalism allows for the treatment of spin-orbit coupling effects, accounts for nuclear vibrations in the form of a vibrational heat-bath, and naturally incorporates (auto)ionization effects. Apart from describing the theory behind and the program workflow, the paper also contains examples of its application to the simulations of the linear L$_{2,3}$ absorption spectra of titanium complex, high harmonic generation in the hydrogen molecule, ultrafast charge migration in benzene and iodoacetylene, and spin-flip dynamics in the core-excited states of iron complexes.