resumo
The behavior of the dielectric constant epsilon of pure fluids and binary mixtures near liquid-gas and liquid-liquid critical points is studied within the concept of complete scaling of asymmetric fluid-fluid criticality. While mixing of the electric field into the scaling fields plays a role, pressure mixing is crucial as the asymptotic behavior of the coexistence-curve diameter in the epsilon-T plane is concerned. Specifically, it is found that the diameters, characterized by a vertical bar T-T-c vertical bar(1-alpha) singularity in the previous scaling formulation [J.V. Sengers, D. Bedeaux, P. Mazur, and S. C. Greer, Physica A 104, 573 (1980)], gain a more dominant vertical bar T-T-c vertical bar(2 beta) term, whose existence is shown to be supported by literature experimental data. The widely known vertical bar T-T-c vertical bar(1-alpha) singularity of epsilon along the critical isopleth in the one-phase region is found to provide information on the effect of electric fields on the liquid-liquid critical temperature: from experimental data it is inferred that T-c usually decreases as the magnitude of the electric field is enhanced. Furthermore, the behavior of mixtures along an isothermal path of approach to criticality is also analyzed: theory explains why the observed anomalies are remarkably higher than those associated to the usual isobaric path.
palavras-chave
CRITICAL SOLUTION POINT; COEXISTENCE-CURVE DIAMETERS; CRITICAL CONSOLUTE POINT; BINARY-LIQUID MIXTURES; VAPOR CRITICAL-POINT; CRITICAL END-POINTS; HEAT-CAPACITY; ELECTRIC-FIELD; CRITICAL-BEHAVIOR; NITROETHANE-CYCLOHEXANE
categoria
Physics
autores
Losada-Perez, P; Perez-Sanchez, G; Cerdeirina, CA; Thoen, J
nossos autores
Germán Pérez-Sánchez
Investigador Júnioragradecimentos
We have benefited from many stimulating discussions with J. V. Sengers and M. A. Anisimov. M. H. W. Chan and S. J. Rzoska kindly provided us with their raw data for reanalysis. Financial support from Xunta de Galicia under Grant No. PGIDIT-06PXIB3832828PR is greatly appreciated. Research of P. L.-P. and G. P.-S. is supported by the Ministerio de Educacion y Ciencia under the "Programa Nacional de Formacion del Profesorado Universitario" (Grants No. AP-2004-2947 and No. AP-2005-1959, respectively).