An optimised molecular model for ammonia |
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Authors: | Sabine H. L. Klapp Jörg R. Silbermann Martin Schoen |
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Affiliation: | 1. Stranski-Laboratorium für Physikalische und Theoretische Chemie, Sekretariat C7 , Technische Universit?t Berlin , Stra?e des 17, Juni 115, D-10623 Berlin, Germany;2. Fakult?t für Mathematik und Naturwissenschaften , Institut für Theoretische Physik, Sekretariat PN 7-1 , Technische Universit?t Berlin , Hardenbergstra?e 36, D-10623 Berlin, Germany sabine.klapp@fluids.tu-ber;4. Stranski-Laboratorium für Physikalische und Theoretische Chemie, Sekretariat C7 , Technische Universit?t Berlin , Stra?e des 17, Juni 115, D-10623 Berlin, Germany |
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Abstract: | Based on molecular dynamics (MD) computer simulations we investigate the dynamic behaviour of a model complex fluid suspension consisting of large (A) particles (the ‘solute’) immersed in a bath of smaller ‘solvent’ (B) particles. The goal is to identify the effect of systematic simplifications (coarse-graining) of the solvent on typical microscopic time correlation functions characterizing the single-particle and collective dynamics of the solute. As a reference system we employ a binary Lennard–Jones mixture of spherical particles with significant differences in particle sizes (σA>σB) and masses (m A>m B). We then replace the original B particles step by step by a reduced number of larger and heavier particles such that the mass and volume fraction of B particles is kept constant. At each step of coarse-graining, the intermolecular interactions between A particles are chosen such that the static A–A structure of the reference system is preserved. Our MD results indicate that coarse-graining has a profound influence on both the single-particle dynamics as reflected by the self-diffusion constant and the collective dynamics represented by the distinct part of the van Hove time correlation function. The latter holds only at intermediate packing fractions, whereas the collective dynamics turns out to be essentially insensitive to coarse-graining at high packing fractions. |
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Keywords: | Course-graining Dynamics Complex fluids Colloidal systems Molecular dynamics |
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