Full dimensional potential energy surfaces (PESs) based on machine learning (ML) techniques provide means for accurate and efficient molecular simulations in the gas- and condensed-phase for various experimental observables ranging from spectroscopy to reaction dynamics. Here, the MLpot extension with PhysNet as the ML-based model for a PES is introduced into the newly developed pyCHARMM API. To illustrate conceiving, validating, refining and using a typical workflow, para-chloro-phenol is considered as an example. The main focus is on how to approach a concrete problem from a practical perspective and applications to spectroscopic observables and the free energy for the -OH torsion in solution are discussed in detail. For the computed IR spectra in the fingerprint region the computations for para-chloro-phenol in water are in good qualitative agreement with experiment carried out in CCl4. Also, relative intensities are largely consistent with experimental findings. The barrier for rotation of the -OH group increases from ∼3.5 kcal/mol in the gas phase to ∼4.1 kcal/mol from simulations in water due to favourable H-bonding interactions of the -OH group with surrounding water molecules.
@article{arxiv.2304.12973,
title = {PhysNet Meets CHARMM: A Framework for Routine Machine Learning / Molecular Mechanics Simulations},
author = {Kaisheng Song and Silvan Käser and Kai Töpfer and Luis Itza Vazquez-Salazar and Markus Meuwly},
journal= {arXiv preprint arXiv:2304.12973},
year = {2023}
}