Molecular dynamics simulations for the prediction of the dielectric spectra of alcohols, glycols and monoethanolamine

Abstract

This version is available at https://strathprints.strath.ac.uk/54062/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the The response of molecular systems to electromagnetic radiation in the microwave region (0.3-300 GHz) has been principally studied experimentally, using broadband dielectric spectroscopy. However, relaxation times corresponding to reorganisation of molecular dipoles due to their interaction with electromagnetic radiation at microwave frequencies are within the scope of modern molecular simulations. In this work, fluctuations of the total dipole moment of a molecular system, obtained through molecular dynamics simulations, are used to determine the dielectric spectra of water, a series of alcohols and glycols, and monoethanolamine. Although the force fields employed in this study have principally been developed to describe thermodynamic properties, most them give fairly good predictions of this dynamical property for these systems. However, the inaccuracy of some models and the long simulation times required for the accurate estimation of the static dielectric constant can sometimes be problematic. We show that the use of the experimental value for the static dielectric constant in the calculations, instead of the one predicted by the different models, yields satisfactory results for the dielectric spectra, and hence the heat absorbed from microwaves, avoiding the need for extraordinarily long simulations or re-calibration of molecular models.

The dielectric constant: Reconciling simulation and experiment

“…Another issue that warrants further exploration is the effect of scaling on the dynamic dielectric response of fluids 15,48 . Indeed, it has been recently shown that, at least for some fluids, classical non-polarizable models are able to describe the dynamic response over a wide range of frequencies, provided the simulation results are scaled to match the corresponding experimental static dielectric constant 48 . Application of our scaling approach to those systems would make for interesting future research.…”

Classical molecular dynamics simulation of microwave heating of liquids: The case of water

“…Due to the inability of most available empirical force fields to accurately predict the dielectric response of liquids, Cardona et al 2 suggested using the experimental values of static dielectric constants when computing the frequency-dependent dielectric spectra of these liquids using the Debye relaxation model 20 . Following this suggestion we used the experimental static dielectric constant of water to compute the dielectric spectra of water.…”

Hydrogen bond lifetimes and statistics of aqueous mono‐, di‐ and tri‐ethylene glycol

“…Our MD simulations of 50% mole‐fraction of MEG in water yielded a maximum H‐bond decay time of 60 ps (see τ R of Table ), which is in the same order as the reported dielectric relaxation time, but is not expected to be identical, since the relaxation time primarily is related to the dipole reorientation time. Using a different MD based method, the dielectric relaxation time for pure MEG at 298 K has been reported to be 87 ps when a Debye model was utilized and 71 ps when a Cole‐Davidson model was applied (where MEG was modeled using the OPLS force‐field) …”