# Quantum-Electrodynamical Time-Dependent Density Functional Theory Description of Molecules in Optical Cavities

## TL;DR

This paper introduces a new computational method to study molecules in optical cavities, showing how cavity effects can change molecular binding and structure.

## Contribution

A new quantum-electrodynamical time-dependent DFT method (QED-TDDFT-TP) is introduced for modeling molecules in optical cavities.

## Key findings

- QED-TDDFT-TP achieves good agreement with high-level methods for ground-state energies and polaritonic spectra.
- Cavity confinement significantly alters binding energies and geometries of weakly bound dimers.
- The method offers a computationally efficient and accurate tool for studying cavity-modified molecular interactions.

## Abstract

We introduce a quantum-electrodynamical
time-dependent
density
functional theory with a tensor-product representation (QED-TDDFT-TP)
to model molecules strongly coupled to quantized cavity fields. By
combining real-space electronic wave functions with truncated Fock-space
photon states, the method captures light–matter correlations
at a computational cost close to standard DFT. Benchmark calculations
show good agreement with QED-FCI and QED-CASCI for ground-state energies
and polaritonic spectra. Applications to weakly bound dimersincluding
(H2)2, Ar2, (H2O)2, and HFdemonstrate that cavity confinement can significantly
alter binding energies and geometries in a polarization-dependent
manner. The framework provides an accurate and scalable tool for studying
cavity-modified molecular structure and interactions.