Year: 2025
Type: article
Abstract: The Debye relaxation in alcohols has generally been attributed to "collective motion" driven by hydrogen bonding, but the molecular mechanism of relaxation has yet to be conclusively identified. Taking methanol as a model alcohol, we apply an oscillating electric field in molecular dynamics simulations to directly evaluate the molecular motions and identify the mechanism. Methanol forms short-lived chains of hydrogen-bonded molecules through the hydroxyl group. We find that the hydroxyl group rotates in response to the field with a frequency dependence that tracks the Debye peak, implicating these chains in the Debye relaxation. Focusing on the hydroxyl OH rotation, we consider the events (e.g., diffusion of chains, birth, growth) over the lifetime of chains that could contribute to this frequency dependence. We find that molecular participation in chains is responsible for the OH alignment relative to the field: molecules align incrementally, ″clicking in″ during chain formation and during molecular addition to existing chains.
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Awards: G304139194, G4944172283, PURPOSE: THE PURPOSE OF THIS GRANT IS TO INCREASE THE ACCURACY OF COMPUTATIONAL DIELECTRIC SPECTROSCOPY AND DEVELOP COMPUTATIONAL ACOUSTIC SPECTROSCOPY TO HELP THE CHEMICAL INDUSTRY DEVELOP IMPROVED SEPARATIONS TECHNOLOGIES THAT LEVERAGE THE ION PAIRING AND SOLVATION ON STRUCTURE OF SPECIES IN SOLUTION.ACTIVITIES TO BE PERFORMED:THE RESEARCHER WILL USE MOLECULAR DYNAMICS TO MODEL SOLVENTS, MIXTURES, AND SOLUTIONS. THE DIELECTRIC SPECTRUM WILL BE CONSTRUCTED USING THE DIRECT ELECTRIC FIELD METHOD, AND THE ACOUSTIC SPECTRUM WILL BE CONSTRUCTED USING SIMULATED PRESSURE WAVES. THE ACOUSTIC PORTION OF THE PROJECT WILL REQUIRE METHODS DEVELOPMENTS, AS THESE SIMULATIONS HAVE NOT BEEN DESCRIBED IN THE LITERATURE PRIOR TO NOW.EXPECTED OUTCOMES:THE RESEARCHER WILL PRODUCE DIELECTRIC AND ACOUSTIC SPECTRA THAT CAN BE USED TO UNDERSTAND ION PAIRING AND SOLVATION IN SOLUTION.INTENDED BENEFICIARIES:THE MODELING TOOLS CAN BE USED BY OTHER RESEARCHERS IN THIS FIELD, AND RESEARCHERS WHO FOCUS ON INDUSTRIALLY RELEVANT CHEMICAL SEPARATIONS.SUBRECIPIENT ACTIVITIES:THE RECIPIENT DOES NOT INTEND TO SUBAWARD FUNDS., National Research Service Award-Medical Scientist
OpenAlex ID: W4413533084