Description Of Surface Tension Research Articles

Interfacial-curvature-driven coarsening in mass-conserved reaction-diffusion systems

Mass conservation in chemical species appears in a broad class of reaction-diffusion systems (RDs) and is known to bring about coarsening of the pattern in chemical concentration. Recent theoretical studies on RDs with mass conservation (MCRDs) reported that the interfacial curvature between two states contributes to the coarsening process, reminiscent of phase separation phenomena. However, since MCRDs do not presuppose a variational principle, it is largely unknown whether description of surface tension is operative or not. In this study, we numerically and theoretically explore the coarsening process of patterns in MCRDs in two and three dimensions. We identify the parameter regions where the homogeneous steady state becomes stable, unstable, and metastable. In the unstable region, pattern formation is triggered by usual Turing instability, whereas in the metastable region, nucleation-growth-type pattern formation is observed. In the later stage, spherical droplet patterns are observed in both regions, where they obey a relation similar to the Young-Laplace law and coarsen following the evaporation-condensation mechanism. These results demonstrate that in the presence of a conserved variable, a physical quantity similar to surface tension is relevant to MCRDs, which provides new insight into molecular self-assembly driven by chemical reactions.

Local description of surface tension through thermodynamic and mechanical definitions

For a half century, the calculation of local pressure components and surface tension along the normal to the surface have been carried out using mechanical definitions. This has led to three principal definitions: Irving and Kirkwood, Harasima and Kirkwood–Buff. Recently, thermodynamic definitions based on the energy calculation have been introduced to compute the local properties. We propose here to compare both definitions for Lennard–Jones particles interacting through a truncated and shifted potential. For this, two locations of the pairwise interaction involved in the calculation of the local pressure components and surface tension within the thermodynamic routes are investigated. For the first time, we show that the thermodynamic definition suffers, to one least degree with respect to the mechanical definition, from the same ambiguity. From a numerical standpoint, thermodynamic definition is more simple and less computationally expensive. Therefore, with the complicated potential, the thermodynamic approach appears to be most interesting to compute macroscopic and local pressure and surface tension.

Three typical sizes of spherical drops in vapor phase

The effects of the molecular theory of distorted vapor-liquid boundary surfaces are discussed within the framework of the lattice gas model for spherical drops that are present in the vapor phase. It is shown that three typical scales of drop size ρ can be defined, corresponding to: (1) the critical value of ρ0 at the beginning of phase formation related to the emergence of surface tension of the dense phase; (2) the value of radius ρt, above which the thermodynamic description of surface tension of a drop is reasonable and both discreteness of the compound and contributions of spontaneous fluctuations can be ignored; and (3) the value of radius ρb, above which the values of surface tension are close to the volume value, upon small surface distortions of large drops.

One-fluid theory of liquid-vapor surface tension in simple multi-component mixtures

We propose a theory of surface tension in multi-component mixtures of simple fluids far from critical conditions based on the one-fluid van der Waals approximation and statistical mechanical perturbation approach. The theory contains no adjustable parameters. By comparison with molecular dynamics simulation of binary Lennard-Jones mixtures it is shown that the theory provides a quantitative (within a tolerance of ∼15%–20%) description of surface tension.

SOME THERMODYNAMIC CONSIDERATIONS OF SURFACE REGIONS: SURFACE TENSION, ADSORPTION, AND ADSORPTION HYSTERESIS

Thermodynamic conditions for equilibrium between bodies which exert forces upon one another are discussed. The two bodies are treated as assemblies of infinitesimal volumes of pure components and the influence of the mutual potential fields examined. The results provide a thermodynamic description of surface tension and certain types of adsorption phenomena, as well as throwing considerable light on adsorption hysteresis.