Relative Permittivity of Dipolar Model Fluids from Molecular Simulation and from the Co-Oriented Fluid Functional Equation for Electrostatic Interactions

Abstract

The relative permittivity of dipolar fluids is important in many industrial and scientific applications, e.g. whenever electrolytes or electromagnetic fields are present. For non-polarizable model molecules, it is directly linked to the mutual molecular orientation and thereby usually not accessible by equations of state. However, the recently developed Co-Oriented Fluid Functional Equation for Electrostatic interactions (COFFEE) allows for calculating the orientation

Relative Permittivity of Stockmayer-Type Model Fluids from MD Simulations and COFFEE

“…As in our previous work, , we study Stockmayer-type model fluids that consist of the Lennard-Jones (LJ) potential and a superimposed point dipole, resulting in the total potential energy U of a system of N particles given by Here, σ LJ and ϵ LJ are the LJ size and energy parameters, respectively, r ij is the distance between particles i and j , is the distance between the dipoles on particles i and j , ε 0 is the vacuum permittivity, μ is the magnitude of the dipole moment, and φ i ′, φ j ′, and γ ij ′ are the angles describing the mutual orientation of the dipoles. Figure shows a depiction of the angles in the dipole–dipole potentials used in the present work.…”

“…28 In a previous work, using a comparison to molecular simulation data we have shown that COFFEE is able to predict the relative permittivity of Stockmayer-type model fluids in the saturated liquid and vapor states, at least qualitatively. 29,30 In this work, we extend this study to the homogeneous liquid, vapor, and supercritical regions. We assess the predictions obtained with COFFEE 27 for the relative permittivity of Stockmayer-type model fluids by comparison with results from molecular dynamics (MD) simulations.…”

“…COFFEE. We follow the approach presented in our previous work 29 for obtaining predictive results for the relative permittivity of the model fluids with a perturbation theory: we use COFFEE, 27 which is a perturbation theory that contains information on the mutual orientation of molecular dipole moments in the form of the orientation distribution function (ODF) O(ξ i , ξ j , γ ij ), where ξ i = cos φ i ′ and ξ j = cos φ j ′ (cf. Figure 1).…”

ms2: A molecular simulation tool for thermodynamic properties, release 3.0

“…The ODF quantifies how neighboring molecules are mutually oriented. Such information on the fluid structure is useful for the parametrization of equations of state that give access to the relative permittivity [23,24].…”

“…In addition to previous validations of the ms2 implementation [24,34,35] by comparison to literature data, the dielectric constant of two water models and two methanol models at ambient conditions was computed with ms2. Again, the reaction field method with conducting boundary conditions was used to treat longrange electrostatics.…”