Molecular dynamics simulation of microwave heating of liquid monoethanolamine (MEA): An evaluation of existing force fields.

Abstract

We present a complete classical molecular dynamics (MD) study of the dielectric heating of liquid monoethanolamine (MEA) at microwave (MW) frequencies ranging from 1.0 to 10.0 GHz. The detailed dielectric properties predicted by a series of existing empirical force fields of MEA were carefully compared to experimental results. We find that all the evaluated force fields were unable to accurately predict experimental static dielectric constant, frequency-dependent dielectric spectra, and MW heating profiles of liquid MEA, although GROMOS-aa (all-atom GROningen molecular simulation) is the most accurate of those tested. With an isotropic scaling of partial atomic charges, the modified GROMOS-aa and OPLS-aa (all-atom optimized potentials for liquid simulations) force fields could accurately reproduce the experimental static dielectric constant and frequency-dependent dielectric spectra, but they failed to predict MW heating rates directly from MD heating simulations. Thus, the recently presented approach [F. J. Salas et al., J. Chem. Theory Comput. 11, 683 (2015); A. P. de la Luz et al., ibid. 11, 2792 (2015)] to tune existing force fields is not an ideal approach to produce force fields suitable for accurate dielectric heating studies.