Efficient simulation of multielectron dynamics in molecules under intense laser pulses: implementation of the multiconfiguration time-dependent Hartree–Fock method based on the adaptive finite element method

Abstract

We present an implementation of the multiconfiguration time-dependent Hartree–Fock method based on the adaptive finite element method for molecules under intense laser pulses. For efficient simulations, orbital functions are propagated by a stable propagator using the short iterative Arnoldi scheme and our implementation is parallelized for distributed memory computing. This is demonstrated by simulating high-harmonic generation from a water molecule and achieves a simulation of multielectron dynamics with overwhelmingly less computational time, compared to our previous work [Sawada, R. et al. Phys. Rev. A, 2016, 93, 023434].

Use of Erfgau Potential for Simulations of Multielectron Dynamics in Intense Laser Pulses

“…The time evolution of expansion coefficients and orbitals is handled using the same method reported in ref . In this approach, the equations of motion for all orbitals and expansion coefficients are treated as a single large linear matrix equation and are evolved by using the Short Iterative Arnoldi method. , This propagator, which can stably handle time evolution including nonlinear terms, is well suited for this simulator since the FEDVR basis has not only high accuracy but also high momentum components.…”

“…Generally speaking, the MCTDHF simulations based on three-dimensional Cartesian coordinates for molecules are computationally highly expensive. In our recent publication, we achieved such simulations for water molecules by leveraging the adaptive finite element method, a stable time-evolution method, and distributed parallel computing. Our current molecular implementation assumes the use of the erfgau potential, thereby reducing the need for high spatial resolution compared to our previous work .…”

“…In our recent publication, we achieved such simulations for water molecules by leveraging the adaptive finite element method, a stable time-evolution method, and distributed parallel computing. Our current molecular implementation assumes the use of the erfgau potential, thereby reducing the need for high spatial resolution compared to our previous work . However, given the direct discretization in the three-dimensional space, it requires handling approximately 10 million degrees of freedom.…”

“…Our current molecular implementation assumes the use of the erfgau potential, thereby reducing the need for high spatial resolution compared to our previous work. 22 However, given the direct discretization in the three-dimensional space, it requires handling approximately 10 million degrees of freedom. To address this computational challenge, we employ a GPU to run this simulator, achieving rapid simulations.…”

Implementation of the Time-Dependent Complete-Active-Space Self-Consistent-Field Method for Diatomic Molecules

“…However, extending the utility of these methods to molecular systems presents formidable challenges, primarily due to the absence of straightforward and efficient methods for discretizing three-dimensional space, as is commonly done for atomic systems with a spherical symmetry. ,, Thus, the discretization of atoms using spherical coordinates becomes inapplicable without relying on specific system symmetries. To address this issue, an innovative approach employs multiresolution grids, , offering a viable means to simulate general molecular systems without incurring prohibitive computational expenses.…”