2 research outputs found
Interfacial Tensions near Critical Endpoints: Experimental Checks of EdGF Theory
Predictions of the extended de Gennes-Fisher local-functional theory for the
universal scaling functions of interfacial tensions near critical endpoints are
compared with experimental data. Various observations of the binary mixture
isobutyric acid water are correlated to facilitate an analysis of the
experiments of Nagarajan, Webb and Widom who observed the vapor-liquid
interfacial tension as a function of {\it both} temperature and density.
Antonow's rule is confirmed and, with the aid of previously studied {\it
universal amplitude ratios}, the crucial analytic ``background'' contribution
to the surface tension near the endpoint is estimated. The residual singular
behavior thus uncovered is consistent with the theoretical scaling predictions
and confirms the expected lack of symmetry in . A searching test of
theory, however, demands more precise and extensive experiments; furthermore,
the analysis highlights, a previously noted but surprising, three-fold
discrepancy in the magnitude of the surface tension of isobutyric acid
water relative to other systems.Comment: 6 figure
Scaling for Interfacial Tensions near Critical Endpoints
Parametric scaling representations are obtained and studied for the
asymptotic behavior of interfacial tensions in the \textit{full} neighborhood
of a fluid (or Ising-type) critical endpoint, i.e., as a function \textit{both}
of temperature \textit{and} of density/order parameter \textit{or} chemical
potential/ordering field. Accurate \textit{nonclassical critical exponents} and
reliable estimates for the \textit{universal amplitude ratios} are included
naturally on the basis of the ``extended de Gennes-Fisher'' local-functional
theory. Serious defects in previous scaling treatments are rectified and
complete wetting behavior is represented; however, quantitatively small, but
unphysical residual nonanalyticities on the wetting side of the critical
isotherm are smoothed out ``manually.'' Comparisons with the limited available
observations are presented elsewhere but the theory invites new, searching
experiments and simulations, e.g., for the vapor-liquid interfacial tension on
the two sides of the critical endpoint isotherm for which an amplitude ratio
is predicted.Comment: 42 pages, 6 figures, to appear in Physical Review