jp7b12220_si_001.pdf (4.03 MB)
Molecular Dynamics Investigation of the Influence of the Hydrogen Bond Networks in Ethanol/Water Mixtures on Dielectric Spectra
journal contribution
posted on 2018-01-04, 00:00 authored by Javier Cardona, Martin B. Sweatman, Leo LueThe
dielectric response of fluids to electromagnetic radiation
in the microwave region originates from processes occurring at the
molecular level. Understanding these processes in more detail is relevant
to many fields, such as microwave heating, fluid mixing, and separation
technologies. In this work, we use molecular dynamics (MD) simulations
to study the dielectric spectra of ethanol/water mixtures. We compare
our predictions with experimental results at different compositions.
We show how the dielectric response can be estimated to a high level
of accuracy using three dielectric relaxations: a dominant and slower
process at microwave frequencies and two faster processes. A deeper
study of the dynamics of the hydrogen bond network formed in these
systems reveals how collective processes between the individual species
are the origin of the final dielectric response. Our results agree
with the “wait-and-switch” mechanism, which describes
the dynamics of the hydrogen bond network as the combination of two
processes: the fast breakage and formation of individual hydrogen
bonds and the subsequent reorganization of the entire network once
this process becomes energetically favorable. Since the dielectric
response is related to dipole reorientations in the system, it is
directly linked to these mechanisms.