Computer simulations of strongly interacting dipolar systems: performance of a truncated Ewald sum

Abstract

Using strongly interacting, three-dimensional dipolar fluids as model systems we compare computer simulation results obtained with the full, conventional Ewald summation with results based on a truncated Ewald sum. The truncation consists of entirely neglecting the Fourier part of the full Ewald expression, which saves a large amount of the otherwise required computational time. In order to test the truncated version we consider two types of dipole-driven phase transitions: the isotropic-to-ferroelectric transition of one-component dipolar soft sphere fluids, on one hand, and the demixing transition in mixtures of dipolar and neutral soft spheres, on the other. Comparing various thermodynamic and structural data we find that the truncated Ewald sum yields surprisingly accurate results even at large dipolar coupling strength and even when subtle quantities such as the dielectric constant and the pressure tensor are considered. Our work thus suggests that the truncated version can safely be used to obtain a first estimate of the properties of interest even under strongly coupled conditions.

Keywords:

• Phase transition; Interface; Polar fluids; Ferrofluids; Demixing; Orientational order; Ewald summation

Acknowledgements

It is a pleasure to thank Professor Frank Forstmann for fruitful discussions and suggestions. E.D.H. and J.A. acknowledge CONCYT-Mexico (L0080-E9607) for financial support. S.H.L.K. acknowledges financial support from the Deutsche Forschungsgemeinschaft through the Emmy-Noether Programme and the Sonderforschungsbereich 448 ‘Mesoscopically structured composites’.