Phenomena In Liquid Mixtures Research Articles

Liquid Hopfield model: Retrieval and localization in multicomponent liquid mixtures

Biological mixtures, such as the cellular cytoplasm, are composed of a large number of different components. From this heterogeneity, ordered mesoscopic structures emerge, such as liquid phases with controlled composition. The competition of these structures for the same components raises several questions: what types of interactions allow the retrieval of multiple ordered mesoscopic structures, and what are the physical limitations for the retrieval of said structures. In this work, we develop an analytically tractable model for multicomponent liquids capable of retrieving states with target compositions. We name this model the liquid Hopfield model in reference to corresponding work in the theory of associative neural networks. In this model, we show that nonlinear repulsive interactions are a general requirement for retrieval of target structures. We demonstrate that this is because liquid mixtures at low temperatures tend to transition to phases with few components, a phenomenon that we term localization. Taken together, our results reveal a trade-off between retrieval and localization phenomena in liquid mixtures, and pave the way for other connections between the phenomenologies of neural computation and liquid mixtures.

Wetting phenomena and the decay of correlations at fluid interfaces

The physics of wetting in three dimensional systems with planar symmetry is revisited in order to explore the extreme sensitivity to microscopic interactions that underlies even thick film adsorption phenomena in d=3. Beginning with short-ranged models of wetting by liquid at a wall-vapor interface, weighted density functional theory is used to obtain an accurate description of the mean-field interface potential along the entire saturated liquid branch. Well away from the bulk critical point, the long-range decay of this class of interface potentials is damped oscillatory rather than the generally assumed monotonic form. This result is best understood in the context of a recently published general theory of the asymptotic structure of liquids and their mixtures. The inescapable conclusion from mean-field theory is that over much of the saturated liquid curve, complete wetting is replaced by thick film pseudowetting associated with layering phenomena. However, oscillatory structure at microscopic wavelengths is strongly renormalized by the inclusion of capillary-wave fluctuations. To assess this aspect, the paper reviews the explicit linear renormalization group calculation of Chernov and Mikheev [Phys. Rev. Lett. 60, 2488 (1988)]. One must distinguish between two cases: (i) pure wetting, where capillary-wave fluctuations renormalize the decay length of the damped oscillatory structure, and (ii) wetting in the presence of external capillary-wave damping (such as Earth's gravity), where the renormalization can dramatically reduce an oscillatory amplitude but cannot formally prevent the suppression of complete wetting.The second main aim of the paper is an attempt at a general survey of the plethora of length scales potentially relevant to thick film wetting phenomena in d=3. A full description of short-ranged models of simple fluids is presented in terms of the behavior of monotonic and oscillatory decay lengths along the saturated liquid branch. Additional length scales of the same class arise from competition with exponentially decaying wall fields. Power-law interactions (dispersion forces) lead to a qualitatively different asymptotic regime. Notwithstanding the ultimate dominance of power-law structure at the longest range, moderately thick film wetting should still be influenced by short-ranged intermolecular forces, particularly in mean field. Finally, the equally crucial significance of asymptotic structure to wetting phenomena in liquid mixtures and in charged fluid systems is highlighted and attention drawn to recently published theories of the required asymptotic forms. In summary, the physics of wetting phenomena in three-dimensional systems is probably close to being fully understood, but the resulting picture for typical experimental systems is amazingly complex.

Influence of a third component on (liquid + liquid) phase equilibria in (butan-2-ol + water) and in (butan-1-ol + water) at pressures up to 160 MPa

(Liquid + liquid) phase equilibria of (butan-2-ol + water) and (butan-1-ol + water) have been investigated in the temperature range from 255 K to 400 K and at pressures up to 160 MPa in an optical high-pressure cell according to the synthetic method. The mutual miscibilities have either been influenced by substituting fractions of the alkanol by another isomeric butanol or by adding salts to the binary mixtures. For (butan-1-ol + water) a homogeneous region at temperatures below 268 K was found. The p( T) isopleths obtained are presented and discussed; they demonstrate continuous transitions between several different types of immiscibility phenomena in liquid mixtures under high pressures.

Dynamical Lightscattering of Pretransitional Phenomena in Liquid Mixtures

AbstractWe report measurements of the scattering intensity and of the autocorrelation function of the pseudo binary mixture guaiacol/glycerol‐water as a function of temperature and water content. The guaiacol glycerol ratio was kept constant 1:1, while the mass ratio of water/glycerol varied between 0.4% < x < 1.4%. The system shows a closed solubility loop if x > 1.17%. A phenomenological model for the temperature dependence of the interaction parameter is used in order to describe the scattering intensity and the diffusion coefficient as function of temperature.

Positron annihilation in the vicinity of the critical solution point of methanol-cyclohexane mixtures

The positron annihilation method was used to investigate critical phenomena in liquid mixtures of methanol and cyclohexane. Anomalies in the annihilation parameters near the critical solution temperature were found.