Polarizable Transferable Anisotropic United-Atom Force Field Based on the Mie Potential for Phase Equilibria: Ethers, n-Alkanes, and Nitrogen

Abstract

This study proposes a Polarizable Transferable Anisotropic Mie (P-TAMie) force field for ethers and mixtures of ethers with n-alkanes and nitrogen. In our approach, polarizability is accounted for using a charge-on-spring model (also referred to as the Drude model or core−shell model) placed on every united-atom site. Parameters for polarizabilities are obtained from ab initio calculations, without the need to introduce empirical scaling factors. The van der Waals parameters and static partial charges are optimized to minimize deviations to experimental vapor pressure and coexisting liquid density data. Vapor−liquid phase equilibria are calculated using Monte Carlo simulations in the grand canonical ensemble, using a MC scheme with multiparticle moves. Correlation results for pure substances and predictions of mixture behavior obtained from the proposed polarizable force field (P-TAMie) are in good agreement with experimental data. We compare the polarizable force field with an analogous nonpolarizable force field, namely, the Transferable Anisotropic Mie (TAMie) force field, where both force fields share the same intramolecular force field and were parametrized using the same objective function. The comparison should thus single out the role of polarizability in predicting phase equilibria. The comparison of P-TAMie with the nonpolarizable TAMie force field, however, shows very similar results of both models. This study does not include water and aqueous mixtures or other pronounced polar substances.

Integration of Simulated and Experimentally Determined Thermophysical Properties of Aqueous Mixtures by ThermoML

“…However, the results for polarizable force fields are still conflicting . For binary mixtures of ethers with n-alkanes or nitrogen, polarizable and nonpolarizable force fields performed similarly . A polarizable acetone model in aqueous mixtures performed better than nonpolarizable models for heat of vaporization and dielectric permittivity, but worse for diffusion .…”

“…33 For binary mixtures of ethers with n-alkanes or nitrogen, polarizable and nonpolarizable force fields performed similarly. 34 A polarizable acetone model in aqueous mixtures performed better than nonpolarizable models for heat of vaporization and dielectric permittivity, but worse for diffusion. 35 For mixtures of ionic liquids with various polar and nonpolar compounds, polarizable force fields reproduced well the experimental densities, diffusion coefficients, and viscosities.…”

Molecular Modeling of Water-in-Salt Electrolytes: A Comprehensive Analysis of Polarization Effects and Force Field Parameters in Molecular Dynamics Simulations

“…The Drude oscillator model , (also referred to as the core–shell or charge-on-spring model , ) explicitly accounts for the dynamics of the electric dipole moments on polarizable atoms. In this model, the polarizable atom consists of a pair of charged particles, i.e., a negatively charged Drude particle (DP or shell) and a positively charged Drude core (DC).…”

Construction of a Polarizable Force Field for Molecular Dynamics Simulation of a NaOTF Water-In-Salt Electrolyte

“…The Drude oscillator model 32,37 (also referred to as the core-shell model or charge-on-spring model [38][39] ) is used to explicitly account for the dynamics of the electric dipole moments on polarizable atoms. In this model, a so-called Drude particle (also called a shell 40 ) is added to each polarizable atom to form a pair of oppositely charged particles: a positively charged Drude core (DC) carrying the majority of the atomic mass and a negatively charged Drude particle (DP) modeling a fluctuating electron cloud whose center can be displaced from the atom core.…”