# DMRG/FQ: A Polarizable Embedding Approach Combining Density Matrix Renormalization Group and Fluctuating Charges

## TL;DR

This paper introduces a new method combining DMRG and fluctuating charges to accurately simulate electronic excited states in solvated systems.

## Contribution

The novel DMRG/FQ approach enables accurate modeling of solvent polarization in electronic excited states.

## Key findings

- The method yields reliable excitation energies and solvatochromic shifts.
- It shows close agreement with experimental data for solvated systems.
- Mutual polarization is critical for solute–solvent interactions in hydrogen-bonded systems.

## Abstract

We present an integrated multiscale framework that combines
the
Density Matrix Renormalization Group (DMRG) with a polarizable fluctuating-charge
(FQ) force field for the simulation of electronic excited states in
solution. The method exploits the capabilities of DMRG to accurately
describe systems with strong static correlation, while the FQ model
provides a self-consistent and physically grounded representation
of solvent polarization within a QM/MM embedding. The DMRG/FQ approach
is applied to representative solvated systems, using extensive molecular
dynamics sampling. The method yields reliable excitation energies,
solvatochromic shifts, and a close agreement with available experimental
data. The results highlight the importance of mutual polarization
for capturing specific solute–solvent interactions, particularly
in systems where hydrogen bonding or directional interactions play
a dominant role.