China
Africa
Explore chapters and articles related to this topic
The Liquid-Vapor Interfacial Region: A Nanoscale Perspective
Published in Van P. Carey, Liquid-Vapor Phase-Change Phenomena, 2020
The characteristics of the interfacial region can be explored in a more quantitative way by extending classical thermodynamic analysis to the interfacial region with the idealization that properties vary continuously across the region and that local thermodynamic equilibrium applies in a time averaged sense within small control volumes within the interfacial region. This approach was pioneered by van der Waals [1.6] and is usually referred to as the van der Waals theory of capillarity or the molecular theory of capillarity. It is also sometimes referred to as a mean field theory because it is based on the idealization that the behavior of each molecule in a localized region is dictated by the mean field associated with the surrounding molecules.
The Liquid-Vapor Interfacial Region – A Nanoscale Perspective
Published in Van P. Carey, Liquid-Vapor Phase-Change Phenomena, 2018
The characteristics of the interfacial region can be explored in a more quantitative way by extending classical thermodynamic analysis to the interfacial region with the idealization that properties vary continuously across the region and that local thermodynamic equilibrium applies in a time averaged sense within small control volumes within the interfacial region. This approach was pioneered by van der Waals [1.6] and is usually referred to as the van der Waals theory of capillarity or the molecular theory of capillarity. It is also sometimes referred to as a mean field theory because it is based on the idealization that the behavior of each molecule in a localized region is dictated by the mean field associated with the surrounding molecules.
Ion Size Correlations in Electric Double Layers
Published in Victor M. Starov, Nanoscience, 2010
M. Quesada-Pérez, A. Martín-Molina, J. G. Ibarra-Armenta, R. Hidalgo-Álvarez
The Gouy–Chapman (GC) model, the cornerstone of which is the Poisson–Boltzmann (PB) equation, has been the traditional approach for describing the electric double layer (EDL) of colloids for many years. However, this mean-field theory ignores certain correlations (e.g., those due to finite ion size) that might produce wrong results in some cases. For instance, since the early 1980s itis well known that the PB equation would fail to study EDLs with multivalent counterions. Some fascinating phenomena (such as overcharging and the existence of attractive forces between equally charged particles) take place in the presence of these kinds of ions and they cannot be justified easily from the classical approach [1–5].
Generalization of the Maier-Saupe theory to the ferroelectric nematic phase
Published in Liquid Crystals, 2022
J. Etxebarria, C. L. Folcia, J. Ortega
The Maier-Saupe (MS) theory is one of the most successful theories in the physics of nematic liquid crystals [1–3]. This theory gives a basic explanation for the existence of the nematic order and correctly describes the order of magnitude of the degree of that order. Despite its simplicity, the theory is amazingly successful in describing the nematic-isotropic (N-I) phase transition and the temperature dependence of optical anisotropy and dielectric and magnetic susceptibilities in the N phase. Obviously the theory has its own limitations. Being a mean field theory, it does not take into account the correlations in the orientations and positions between neighbouring molecules, and this is reflected in deviations of some of the theoretical predictions compared to the experimental behaviour. Furthermore, the mean field potential is described by a particularly simple model based only on a single parameter, which gives rise to further limitations for the theory. Thus, the theory predicts a universal dependence of the order parameter on the reduced temperature, which is not entirely in accordance with the observations. Anyway, the theory is a very valuable first approximation for describing many of the properties of ordinary nematics.