Time-dependent restricted-active-space self-consistent field theory for laser-driven many-electron dynamics

TL;DR

The paper introduces the TD-RASSCF method, a new computational approach for simulating many-electron dynamics under strong laser fields, offering improved efficiency over existing methods.

Contribution

It generalizes the MCTDHF theory by integrating the restricted-active-space scheme, enabling accurate wave function construction with fewer configurations.

Findings

Accurately reproduces high-order harmonic generation spectra

Reduces computational complexity compared to MCTDHF

Potential to simulate larger atoms and molecules

Abstract

We present the time-dependent restricted-active-space self-consistent field (TD-RASSCF) theory as a new framework for the time-dependent many-electron problem. The theory generalizes the multiconfigurational time-dependent Hartree-Fock (MCTDHF) theory by incorporating the restricted-active-space scheme well known in time-independent quantum chemistry. Optimization of the orbitals as well as the expansion coefficients at each time step makes it possible to construct the wave function accurately while using only a relatively small number of electronic configurations. In numerical calculations of high-order harmonic generation spectra of a one-dimensional model of atomic beryllium interacting with a strong laser pulse, the TD-RASSCF method is reasonably accurate while largely reducing the computational complexity. The TD-RASSCF method has the potential to treat large atoms and molecules beyond the capability of the MCTDHF method.