On the Calculation of the Dielectric Permittivity and Relaxation of Molecular Models in the Liquid Phase.

Methodology to compute the relative static dielectric permittivity and dielectric relaxation time of molecular liquids is reviewed and explicit formulas are given for the external field method in the case of simulations using a spherical cutoff, in which the background dielectric permittivity (εcs) can be larger than one, in combination with a Poisson-Boltzmann reaction-field approximation for long-range electrostatic interactions. The external field method is simple to implement and computationally efficient. It is particularly suitable for polarizable molecular models with zero permanent dipole moment and for coarse-grained molecular models with εcs > 1. The dielectric permittivities and relaxation times of water (H2O), dimethylsulfoxide (DMSO), methanol (MeOH), and chloroform (CHCl3), which range from 2 to 80 and from 5 ps to 50 ps, respectively, were calculated as an illustration.