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.
Supplementary materials
Title
Supporting Materials for: Nuclear Quantum effects in Gas-Phase 2-Fluoroethanol
Description
A set of additional tables and figures are provided. These include a comparison of relative energies of minima at various levels of theory, harmonic frequencies of various stationary points at the MP2/aug-cc-pVTZ level of theory, errors in the fitted internals, umbrella sampling parameters, PES quality with a quartic potential, trends of key internals from PIMD simulations, 2D (phi1, phi2) distributions from umbrella sampling simulations, radii of gyration of the ring polymers of all atoms as a function of phi1 at 300 K and 50 K from umbrella sampling simulations. The Fortran 90 code for the PES for 2FE is available here: https://github.com/arandharamrinal/2FE.
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Supplementary weblinks
Title
Potential Energy Surface for Gas-Phase 2-Fluoroethanol
Description
Fortran codes for the calculations of the potential and forces at an input geometry are provided. The full description of the potential model and construction are provided in the main article.
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