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

Abstract

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.

Keywords::

• dielectric spectra
• microwaves
• molecular dynamics
• alcohols
• monoethanolamine

Acknowledgements

The authors gratefully acknowledge the support of the Department of Chemical and Process Engineering at the University of Strathclyde and the School of Engineering at the University of Edinburgh, as well as the Engineering and Physical Sciences Research Council (EPSRC).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Results were obtained using the EPSRC funded ARCHIE-WeSt High Performance Computer (www.archie-west.ac.uk) [grant number EP/K000586/1].