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A modification of the Wolf method [ Wolf et al. J. Chem. Phys. 1999 , 110 , 8254 - 8282 ], a spherically truncated pairwise summation to evaluate electrostatic interactions efficiently, is proposed. This method achieves better results for the energy, and the approach is used for determining phase equilibria in the grand canonical ensemble. To assess optimal parameters for the Wolf summation we propose a simple iterative approach using the Ewald summation as a reference. We show that phase equilibrium properties for pure components as well as mixtures can be calculated accurately using the Wolf summation. Our study considers molecular fluids with partial charges but without net charge.

We present an approach to calculate interfacial resistivities against mass and heat transfer at a vapor–liquid interface. Classical density functional theory is combined with the perturbed chain statistical associating fluid theory (PC-SAFT) equation of state to calculate continuous density profiles and (partial molar) enthalpy profiles across the interface. We follow the approach of Glavatskiy and Bedeaux [Glavatskiy, K.; Bedeaux, D. J. Chem. Phys. 2010, 133, 144709] where the resistivity for heat and mass transport and the coupled resistivities of an interface are obtained by integrating over local resistivities across an interface. This formalism is applied to pure component systems and to binary mixtures. We compare our results to previously published results from nonequilibrium molecular dynamic (NEMD) simulations for argon and n-octane. Two constant parameters have to be adjusted to NEMD simulations for each local resistivity profile. Very good agreement was found for both pure component systems. The results for binary mixtures are in very satisfying agreement to results from NEMD simulations. This study is the first to combine a physically based approach with integral relations not only for model fluids but also for real components and binary mixtures.

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The Wolf method for calculation of electrostatic interactions in molecular simulations is known to describe the energy well, whereas the forces have discontinuities. For a more reliable description of the forces this method can be extended with a shifted force approach. This leads to a good description of the forces and precise molecular dynamics simulation, but the description of the energy becomes poorer. In this study we propose a modification of a shifted force extension to describe the energy as well as the forces in better agreement to reference data as determined from the Ewald summation. We show that vapor−liquid phase equilibria (VLE) calculated with Monte Carlo simulations in the grand canonical ensemble and dynamic properties calculated with molecular dynamics simulations can be calculated reliably using this modification to describe the electrostatic interactions.