resumo
In this work, the entropy based scaling laws of Rosenfeld, Dzugutov and Bretonnet, which connect reduced self-diffusion coefficients (D*) with residual entropy (named excess entropy in this field), were analysed in order to test their attributed universal character. With this purpose, an extensive database with 1727 molecular dynamic and experimental values was compiled for hard-sphere (HS), Lennard-Jones (LJ), hard-sphere chain (HSC), and real (polar, nonpolar, symmetrical and asymmetrical) fluids. It was shown that these equations fail when tested over the entire range of density and temperature (through residual entropy), even for atomic and simple fluids (e.g., HS and LJ) for which they have been originally proposed. Furthermore, the dependence of the self-diffusivities upon both residual entropy and a molecular chain length parameter (r) was clearly found on the basis of HSC and real data. Accordingly, a new universal correlation for the estimation of D* as function of residual entropy and r was obtained, giving rise to an average absolute relative deviation of 9.13% for all database. It was also devised a very simple and accurate entropy based equation for spherical systems (HS and LJ) which provides only 4.61% of error. The original Rosenfeld, Dzugutov and Bretonnet's expressions attain deviations that are several orders of magnitude higher than our values. (C) 2012 Elsevier Ltd. All rights reserved.
palavras-chave
EQUATION-OF-STATE; LENNARD-JONES FLUID; SIMPLE DENSE FLUIDS; HARD-SPHERE FLUID; TRANSPORT-COEFFICIENTS; MOLECULAR-DYNAMICS; CARBON-DIOXIDE; HIGH-PRESSURE; ATTRACTIVE FORCES; LIQUID
categoria
Engineering
autores
Vaz, RV; Magalhaes, AL; Fernandes, DLA; Silva, CM
nossos autores
Ana Luísa Carvalho Magalhães
Bolseiro de pós-Doutoramento
Carlos Manuel Silva
Professor associado
Graça Raquel Veiga Vaz
Estudante de doutoramentoagradecimentos
R. V. Vaz., A. L. Magalhaes and D. L. A. Fernandes thank financial support provided by Fundacao para a Ciencia e a Tecnologia (PhD grants SFRH/BD/69257/2010 and SFRH/BD/46776/2008, and post doc grant SFRH/BPD/65482/2009, respectively).