Nuclear Quantum Effects in Gas-Phase 2-Fluoroethanol

Abstract

Torsional motions along the FCCO and HOCC dihedrals lead to the five unique conformations of 2-fluoroethanol. In this work, we explore how nuclear quantum effects (NQEs) are manifest in the intramolecular landscape along these two dihedrals, through the use of path integral simulations. We have first developed a full dimensional potential energy surface using the reaction surface Hamiltonian framework. On this potential, we have carried out path integral molecular dynamics at several temperatures starting from the minimum energy well to explore structural influences of NQEs. With umbrella sampling and metadynamics simulations at 300 K and 50 K, we have explored whether NQEs have effects on the free energy landscape. Significant influences are found near the cis region of the dihedrals, which can be understood through the trends in the radii of gyration of the atomic ring polymers. We have also computed the infrared spectra at 300 K and 50 K with thermostatted ring polymer molecular dynamics simulations, which agrees well with experimental band positions.