Excited state geometry optimization with the density matrix renormalization group as applied to polyenes

TL;DR

This paper advances the methodology for optimizing excited state geometries using the density matrix renormalization group (DMRG), applying it to polyenes to analyze their electronic excited states and identify key features like conical intersections.

Contribution

It introduces a wavefunction maximum overlap technique for state-specific DMRG excited state optimization and applies it to large polyenes, providing detailed insights into their excited state properties.

Findings

Optimized geometries of polyenes up to C20H22.

Identified exciton, soliton, and bimagnon character in excited states.

Evidence for a planar conical intersection.

Abstract

We describe and extend the formalism of state-specific analytic density matrix renormalization group (DMRG) energy gradients, first used by Liu et al (J. Chem. Theor.Comput. 9, 4462 (2013)). We introduce a DMRG wavefunction maximum overlap following technique to facilitate state-specific DMRG excited state optimization. Using DMRG configuration interaction (DMRG-CI) gradients we relax the low-lying singlet states of a series of trans-polyenes up to C20H22. Using the relaxed excited state geometries as well as correlation functions, we elucidate the exciton, soliton, and bimagnon ("single-fission") character of the excited states, and find evidence for a planar conical intersection.