# Sampling molecular conformers in solution with quantum mechanical accuracy at a nearly molecular mechanics cost

## TL;DR

This paper presents a hybrid computational approach combining classical molecular dynamics, clustering, and quantum corrections to accurately evaluate conformer populations in solution at a computational cost comparable to molecular mechanics.

## Contribution

It introduces a novel method that achieves quantum mechanical accuracy in conformer population estimation with nearly molecular mechanics computational cost.

## Key findings

- Successfully applied to cyanin in water solution
- Achieves quantum accuracy with low computational expense
- Provides a quantitative accuracy assessment criterion

## Abstract

We introduce a method to evaluate the relative populations of different conformers of molecular species in solution, aiming at quantum mechanical accuracy, while keeping the computational cost at a nearly molecular-mechanics level. This goal is achieved by combining long classical molecular-dynamics simulations to sample the free-energy landscape of the system, advanced clustering techniques to identify the most relevant conformers, and thermodynamic perturbation theory to correct the resulting populations, using quantum-mechanical energies from density-functional theory. A quantitative criterion for assessing the accuracy thus achieved is proposed. The resulting methodology is demonstrated in the specific case of cyanin (cyanidin-3-glucoside) in water solution.