Showing papers on "Gibbs–Helmholtz equation published in 1992"

Assessment of the mg-bi system

Abstract: The thermodynamic data for the Mg-Bi system have been optimized from measured thermodynamic data. A two-sublattice model for ionic melt was used to express the Gibbs free energy of the liquid phase. The high and low temperature non-stoichiometric Mg3Bi2 compounds were described by a two-sublattice model, Mg3(Va, Bi)2. The experimental thermodynamic and phase diagram data were well reproduced by the optimized thermodynamic data. Parameters describing the Gibbs free energies of the all phases and the calculated phase diagram and thermodynamic functions are presented.

Non-dispersive interactions at liquid/liquid and liquid/solid interfaces

Abstract: Non-dispersive interactions developed at liquid/liquid and liquid/solid interfaces are studied by determining directly (liquid/liquid interface) or indirectly, by contact angle measurements (liquid/solid interface), the variation of the interfacial free energy, γij, according to the Gibbs equation. For the liquid/liquid model, the interface between octane containing small quantities of long-chain aliphatic acids or amines and water is considered. The liquid/solid interfaces are constituted of the same organic solutions in contact with fused silica or with calcite, solids having respectively acid and basic properties. From the Dupre and Gibbs equations, the non-dispersive interaction energies between the acidic or basic organic molecules and water, silica, or calcite have been obtained. If the non-dispersive interaction energy is particularly important for the acid/base couples, it is far from being negligible for the acid/acid or base/base couples. This result can be explained by the existence of polar interactions, by the presence of adsorbed water on the solids, or by an amphoteric behavior of the acidic and basic organic molecules.

Gibbs Ensemble Calculations with an Equation of State: An Application to Vapor-Liquid Equilibria

Abstract: A new modification of the Gibbs ensemble Monte Carlo computer simulation method for fluid phase equilibria is described. The modification is based on a thermodynamic model for the vapor phase, and uses an equation of state to account for the weak interactions between the vapor phase molecules. Reductions in the computational time by 30–40% as compared to the original Gibbs ensemble method are obtained. The algorithm is applied to Lennard-Jones - (12,6) fluids and their mixtures and the results are in good agreement with results obtained from simulations using the full Gibbs ensemble method.

Corrigendum to 'Pore shape evolution by solution transfer: thermodynamics and mechanics'* by T. Reuschl6, L. Trotignon and

Abstract: The chemical potential of a component of the solid in solution is given by the equilibrium condition between the stressed solid and its solution. This condition was first established by Gibbs (1877) for a plane interface and then generalized to any curved interface. It was rederived later by Lehner & Bataille (1985) and Mullins & Sekerka (1985). Gibbs (1877) chose to have the solid and the fluid phases enclosed within rigid walls, thus preventing any exchange of mechanical work between the system (solid + fluid) and the environment. However, in the experience described in our reference paper, samples are subjected to constant stress conditions, which induce a deformation of the samples and thus an exchange of work with the environment. One may wonder if Gibbs’ classical equation is still valid under these conditions which are the usual conditions for creep of rocks by pressure solution. We tried to give an answer to this question by using an approach similar to the Griffith’s crack approach. Our derivation led us to the conclusion that Gibbs’ equation had to be modified to take into account the deformability of the solid. We thus proposed to add an elastic energy term to the classical Gibbs’ equation. The question arose as to whether or not Gibbs’ and Griffith’s approaches are compatible. In this corrigendum we want to correct our previous derivation by showing that it contained some omissions leading to an incorrect conclusion. In the reference paper, we proposed to write the variation AU of the internal energy of the system (solid+fluid) as follows (equation 9 of the reference paper): AU = AQ + AW = AU, + AU, + (uf - us) 6n (9)

Thermodynamics of Adsorption

Abstract: The use of thermodynamics in obtaining information about interfaces is outlined for both fluid/fluid and solid/fluid interfaces. Some of the special problems which arise with interphases containing charged species are indicated. In particular the problem of the location of the charge is discussed. The use of adsorption isotherms is considered.