Shadow excited state molecular dynamics with the \DeltaSCF method

TL;DR

This paper introduces a shadow excited state molecular dynamics method based on eltaSCF within the XL-BOMD framework, improving computational efficiency and stability for excited state simulations.

Contribution

It extends the XL-BOMD method to excited states using eltaSCF, offering a more efficient and stable approach for excited state molecular dynamics.

Findings

Significant reduction in computational cost compared to traditional ESMD.

Enhanced stability and robustness of the shadow ESMD method.

Implementation demonstrated with SCC-DFTB theory, generalizable to other methods.

Abstract

We present an extension of the shadow extended Lagrangian Born-Oppenheimer molecular dynamics (XL-BOMD) method to excited state molecular dynamics (ESMD) in the context of \DeltaSCF Kohn-Sham density functional theory, with demonstrations performed using self-consistent charge density functional tight binding (SCC-DFTB) theory. In this shadow ESMD approach, the approximate iterative solution to the exact potential in conventional ESMD is replaced by an exact single-step solution to an approximate shadow excited-state potential. We show that in addition to offering significant improvement in computational cost relative to direct ESMD, our shadow ESMD method provides enhanced stability and robustness relative to its 'exact' counterpart. Our implementation is carried out in the context of SCC-DFTB theory but should be broadly generalizable, both to {\textit{ab initio}} electronic structure methods and to other semi-empirical quantum chemistry approaches.