Semiphenomenological theory of the Tolman length

A semiphenomenological cluster theory of the curvature correction dT to the surface tension of a spherical liquid drop (known as a ``Tolman length'') is presented. By using the Fisher droplet model of condensation [M. E. Fisher, Physics 3, 255 (1967)]. we obtain an equation relating dT to the saturation vapor pressure at a given temperature T. For low temperatures an analytical solution is obtained. In a general case the equation is solved numerically for various nonpolar substances. Not too close to Tc, dT is found to be positive and of the order of 0.2s, where s is a molecular diameter, in agreement with molecular dynamics simulations. As T¿Tc- the Tolman length becomes negative and diverges, as predicted by the density functional analysis

Semiphenomenological theory of the Tolman length

A semiphenomenological cluster theory of the curvature correction dT to the surface tension of a spherical liquid drop (known as a ``Tolman length'') is presented. By using the Fisher droplet model of condensation [M. E. Fisher, Physics 3, 255 (1967)]. we obtain an equation relating dT to the saturation vapor pressure at a given temperature T. For low temperatures an analytical solution is obtained. In a general case the equation is solved numerically for various nonpolar substances. Not too close to Tc, dT is found to be positive and of the order of 0.2s, where s is a molecular diameter, in agreement with molecular dynamics simulations. As T¿Tc- the Tolman length becomes negative and diverges, as predicted by the density functional analysis

Topological instability of magnetic fluids

A finite volume of a magnetic fluid resting on a solid base in an external homogeneous magnetic field is considered. An approach to the theory of topological instability is proposed and the instability criterion is derived. The shape hysteresis (first order phase transition) for fluids with high magnetic susceptibility is predicted.On a étudié le comportement d'un volume limité de fluide magnétique reposant sur une base solide et placé dans un champ magnétique extérieur homogène. On a obtenu un critère d'instabilité topologique. L'existence de l'hystérésis des formes (transition de phase du 1 er ordre) a été prédite

Cluster Formation at Extreme Supersaturations: Nucleation versus Barrierless Transition

We stuy the process of cluster formation at extreme supersaturations an ientify the temperature-supersaturation omain where evaporation can be neglecte resulting in a barrierless process with kinetics ominate by the imer formation. The cluster size istribution obeys the coalescence equation with the pressure-temperature-epenent association rate coefficients ki, j. In view of the crucial role playe by kinetics uner these extreme conitions, the values of these coefficients calculate within the free molecular collision moel are insufficient for the preiction of the nucleation rate an cluster istribution. An alternative is the use of ki, j obtaine from the ab initio calculations. We apply these consierations to the analysis of recent water nucleation experiments in the postnozzle flow of a Laval nozzle. Theoretical preictions of nucleation rate are in an excellent agreement with experiment. At the same time, there is a iscrepancy in the ensities of small clusters. The latter can be attribute to the ifference in ki, j extracte from the experimental ata an those resulte from the ab initio calculations

Semiphenomenological theory of homogeneous vapor-liquid nucleation

A new semiphenomenological theory of homogeneous vapor–liquid nucleation is proposed. It is based on the Fisher droplet model applied at the saturation point within the framework of the kinetic approach. The microscopic surface tension of a droplet is supposed to have the Tolman form. The unknown Tolman length is naturally identified by equating a known empirical value of saturation pressure psat to the sum of the series over all droplet sizes for psat emerging from the Fisher model. The theory contains no adjustable parameters. Predictions of the new theory for various substances are compared with available experimental data and with the three other widely used theoretical models: classical nucleation theory, corrected Dillmann–Meier and Delale–Meier theory. © 1995 American Institute of Physic

Semiphenomenological effective-medium theory of multicomponent nucleation

We propose an effective-medium approach for homogeneous vapor-liquid nucleation of multicomponent mixtures in the regime of retrograde condensation. Transformation to an effective unary system is accompanied by renormalization of the surface tension. We formulate a generalized Fisher droplet model [M. E. Fisher, Physics 3, 255 (1967)] for the cluster distribution in the effective system. A closed-form expression for the nucleation rate is obtained within the framework of the kinetic approach to nucleation. The theory contains no adjustable parameters. Two- and four-component mixtures of hydrocarbons are studied and theoretical predictions are compared with available experimental data