INAQS, a generic interface for non-adiabatic QM/MM dynamics: Design, implementation, and validation for GROMACS/Q-CHEM simulations

TL;DR

INAQS is an open-source interface that integrates GROMACS and Q-CHEM for non-adiabatic QM/MM simulations, enabling efficient modeling of complex photo-induced processes in large molecular systems.

Contribution

It introduces a flexible, easy-to-adapt software interface for non-adiabatic QM/MM simulations combining GROMACS and Q-CHEM, supporting various dynamics methods.

Findings

Successfully simulated electronic absorption spectra.

Generated free energy surfaces along reaction coordinates.

Modeled excited state dynamics of 1,3-cyclohexadiene.

Abstract

The accurate description of large molecular systems in complex environments remains an ongoing challenge for the field of computational chemistry. This problem is even more pronounced for photo-induced processes, as multiple excited electronic states and their corresponding non-adiabatic couplings must be taken into account. Multiscale approaches such as hybrid quantum mechanics/molecular mechanics (QM/MM) offer a balanced compromise between accuracy and computational burden. Here, we introduce an open-source software package (INAQS) for non-adiabatic QM/MM simulations that bridges the sampling capabilities of the GROMACS MD package and the excited-state infrastructure of the Q-CHEM electronic structure software. The interface is simple and can be adapted easily to other MD codes. The code supports a variety of different trajectory based molecular dynamics, ranging from Born-Oppenheimer to surface hopping dynamics. To illustrate the power of this combination, we simulate electronic absorption spectra, free energy surfaces along a reaction coordinate, and the excited state dynamics of 1,3-cyclohexadiene in solution.