Dynamics of the critical liquid-vapor interface close to a solid wall

We discuss the dynamics of an interface separating two phases of a fluid close to its critical point and in the presence of a third, inert phase regarded as a solid wall. The dispersion relation for the interface undulations is derived and compared with the predictions of the theories of capillary waves and interfacial motion for a conserved order parameter.     

Using the similarity hypothesis in nonisotropic systems close to the liquid-vapor critical point

On the basis of experimental data on the gravitational effect and the molecular scattering of light, the limits of applicability of the similarity hypothesis are investigated in systems subject to the action of a gravitational field close to the liquid-vapor critical point.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 97–100, February, 1979.     

Predicting the liquid-vapor critical point from the crystal anharmonicity

A "universal" dependence is predicted of the reduced critical parameters, k(B)T(c) / E0(gamma), V(c) / V0(gamma), and P(c)V(c)/k(B)T(c) = Z(c)(gamma), on the crystal anharmonicity gamma (closely related to the Gruneisen parameter gamma(G)). It is based on a simplified embedded-atom type approach which enables one to utilize the universal zero-temperature equation of state in a version of fluid perturbation theory. This model's critical temperature and density agree with the experimental results for both the heavy rare gases ( gamma approximately 2.85) and heavy alkali metals ( gamma approximately 1.35). Predicted critical parameters for many other liquid metals are consistent with previous estimates, but the model is not applicable when directional bonding is important.     

Thermodynamic properties of multicomponent mixtures near the liquid-vapor critical point

A new method has been proposed to describe the physical properties of multicomponent mixtures near their critical points. The method is based on the transition from the experimental thermodynamic variables to scaling fields, is applicable to a mixture with any number of the components, and is, thus, universal. For the previously studied methane-propane-pentane mixture, it has been shown that the anomalies of the specific heat at a constant volume and derivative (?P/?T)_ρ,x can be quantitatively described in this approach in a wide vicinity of a critical point, including noncritical isochores.     

Structure of a liquid-vapor interface

The structure of the interface of an argonlike fluid in equilibrium with its own vapor at low temperature is studied using molecular dynamics. The longitudinal pair correlations in the interface are found to be consistent with a simply defined ensemble of local thermodynamic states. However, the transverse correlations exhibit very long-range behavior not predicted by straightforward local thermodynamics. These results strongly suggest that the interface is made up of an ensemble of configurations in each of which the transition from liquid to vapor is locally sharp, but that the transition surface fluctuates strongly in space and time.Supported in part by ERDA, Contract No. EY-76-C-02-3077, and by NSF, Grant DMR-72-03029, through Materials Science Center, Cornell University.The classical theoretical density profile dates back to van der Waals. (1)     

Anomalies in the thermodynamic properties of mixtures near the liquid-vapor critical point

The behavior of the specific heat at constant volume and the derivative (?P/?T)_{ρ, x} has been studied experimentally near the liquid-vapor critical point of the methane-propane-pentane mixture. It has been shown that the derivative ?P/?T)_{ρ, x} for mixtures, in contrast to one-component systems, has a characteristic anomaly directly associated with an anomaly in the specific heat at constant volume. It is impossible to distinguish between the infinite increase in the specific heat or finite peak when processing of the experimental data only for the heat capacity. However, according to the joint analysis of the experimental data for both indicated quantities, both the specific heat of the mixture and the derivative ?P/?T)_{ρ, x} are singular finite quantities.     

Scattering of sound by sound in the vicinity of the liquid-vapor critical point

We report an experimental study of the scattering of sound by sound in the vicinity of the liquid-vapor critical point of carbon dioxide. We measure the amplitude of the scattered difference frequency wave generated by acoustic bulk nonlinearities. We observe that it is strongly increased in the vicinity of the critical point.     

Field and pressure response of Yb compounds close to a quantum critical point

YbCu_5−x Al _x provides the possibility to tune ground state properties by a change of the valence due to the Cu/Al substitution, by pressure as well as by the application of a magnetic field. Near to the critical concentration x _cr≈1.5 non-Fermi-liquid properties (NFL) are obvious, obeying hyperscaling. If magnetic order sets in for x>1.5, the application of moderate magnetic fields quenches order and again NFL features become evident. Hyperscaling in this case indicates strongly interacting spin fluctuations.     

Quantum correction to conductivity close to a ferromagnetic quantum critical point in two dimensions

We study the temperature dependence of the conductivity due to quantum interference processes for a two-dimensional disordered itinerant electron system close to a ferromagnetic quantum critical point. Near the quantum critical point, the crossover between diffusive and ballistic regimes of quantum interference effects occurs at a temperature T*=1/taugamma(E(F)tau)2, where gamma is the parameter associated with the Landau damping of the spin fluctuations, tau is the impurity scattering time, and E(F) is the Fermi energy. For a generic choice of parameters, T* is smaller than the nominal crossover scale 1/tau. In the ballistic quantum critical regime, the conductivity behaves as T1/3.     

How thick is a liquid-vapor interface?

The structure of the interface of an argonlike fluid in equilibrium with its vapor near the triple point is studied using Monte Carlo simulation. By referring particle coordinates to the capillary waves and calculating the transverse structure factor in that reference frame, one can determine the penetration depth of the capillary waves into the bulk as a function of the wave vector. The penetration depth of the lowest capillary mode is consistent with the interfacial thickness as determined from the intrinsic density profile, and the data for the higher modes suggest that the penetration depth might be independent ofk.     

Nonlinear corrections to critical conditions for instability of liquid-liquid charged interface

It is shown that nonlinear corrections to the frequencies of waves arising on a charged interface appear in calculation of the third order of smallness. Because of them, the Tonks-Frenkel critical parameter and wavenumber of the most unstable mode vary in proportion to a small parameter squared. When going through resonance positions, the amplitude coefficients of the corrections change sign. Depending on the wavelength, nonlinear interaction between waves may decrease or increase the critical values of the parameters governing the stability of waves at the interface.     

Simulation of a liquid-vapor interface in an external field

The influence of gravity on the suppression of the capillary fluctuations of a liquid-vapour interface is studied by simulating a Lennard-Jones system in two dimensions in a gravity like field. The results are compared to the capillary wave theory. A lower length cut-off is found for the capillary wavelengths which is an order of magnitude larger than the estimated width of the intrinsic interface.     

Virial theorem for localized states of a quantum particle in classical fluids close to the critical point

Localized states of a light quantum particle, thermalized in a dense classical fluid close to the critical point, obey a simple virial identity as a result of the scaling properties of the host medium. This identity may serve as a self-consistency check for coarse-grained theories of localization.     

Dynamics at the liquid-vapor interface of a supercooled organic glass former

We investigated the dynamics near the liquid-vapor interface of the supercooled model organic glass former dibutyl phthalate by using surface-sensitive x-ray scattering techniques. Our results reveal significant enhancement of the relaxation rate over a wide length-scales range. The analysis of the dispersion relation of long-wavelength surface fluctuations yields a nonzero value of the share modulus near the free surface. At the molecular level, the dynamics in the near surface region (10-15 nm) is inhomogeneous. The mobility is decreasing with increasing distance from the free surface. Below the bulk glass transition, two distinct relaxation times were observed differing by 1 order of magnitude. The observed fast relaxation proves the existence of a high mobility liquidlike surface layer of 10 nm thickness on top of a frozen in bulk system.     

Electric permittivity anomaly close to the critical mixing point: An improved method of estimation of the exponent describing a weak critical anomaly

A critical anomaly of electric permittivity in the vicinity of the consolute critical point of an ethanol and dodecane mixture has been measured and analyzed. A method of analysing the permittivity anomaly, which enhances the credibility of the fitting, has been proposed. We have found out that the exponent predicted in theoretical expectations, 1-α = 0.89, describes the anomaly correctly. However, in spite of the application of the improved method, it is not possible to obtain the value of the fitted critical exponent with satisfying precision.