Nuclear Quantum Effects in Gas-Phase Ethylene Glycol

Path integral molecular simulations are used to explore the nuclear quantum effects (NQEs) on the structure, dihedral landscape and infrared spectrum of ethylene glycol. The simulations are carried out on a new reaction surface Hamiltonian-based model potential energy surface, with especial focus on the role of the OCCO and HOCC dihedrals. By contrast with classical simulations, we analyse how the intramolecular interaction between the OH groups changes due to zero-point effects as well as temperature. These are found to be weak. The NQEs on the free energy profile along the OCCO dihedral are analysed, where notable effects are seen at low temperatures and found to be correlated with the radii of gyration of the atoms. Finally, the power spectrum of the molecule from path integral simulations is compared with the experimental infrared spectrum, yielding good agreement of band positions.