MBE-CASSCF Approach for the Accurate Treatment of Large Active Spaces
Abstract
We present a novel implementation of the complete active space self-consistent field (CASSCF) method that makes use of the many-body expanded full configuration interaction (MBE-FCI) method to incrementally approximate electronic structures within large active spaces. On the basis of a hybrid first-order algorithm employing both Super-CI and quasi-Newton strategies for the optimization of molecular orbitals, we demonstrate both computational efficacy and high accuracy of the resulting MBE-CASSCF method. We assess the performance of our implementation on a set of established numerical tests before applying MBE-CASSCF in the investigation of the triplet-quintet spin gap of iron(II) porphyrin with active spaces as large as 50 electrons in 50 orbitals.
Cite
@article{arxiv.2403.17836,
title = {MBE-CASSCF Approach for the Accurate Treatment of Large Active Spaces},
author = {Jonas Greiner and Ivan Gianni and Tommaso Nottoli and Filippo Lipparini and Janus J. Eriksen and Jürgen Gauss},
journal= {arXiv preprint arXiv:2403.17836},
year = {2024}
}
Comments
27+8 pages, 6 figures. SI as an ancillary file