Gibbs–Duhem equation

About: Gibbs–Duhem equation is a research topic. Over the lifetime, 393 publications have been published within this topic receiving 6248 citations. The topic is also known as: Gibbs-Duhem equation.

Calculation of Entropy Production in Process Models

Abstract: A thermochemical method is presented by which multiphase processes can be simulated with concurrent calculation of the Gibbs energy of the reactive mixture during a chemical change. Algorithmic constraints are set for the overall reaction kinetics when the Lagrange method of undetermined multipliers is used to minimize the Gibbs energy of the multicomponent system. Consequently, the chemical change is calculated as a series of successive “virtual” states, which follow the extent of the overall reaction. From the Gibbs energy of these intermediate states, other thermodynamic quantities for the changing chemical system can be deduced, and the entropy production of the process can be calculated. A particular process model was developed for two isothermal aqueous systems and for a nonisothermal high-temperature process. The entropy production in the reactive systems is presented, and the validity of the simulation models is assessed in terms of their time-dependent Gibbs energy and entropy profiles.

Evaluation Model for Viscosity of Fe–Ni–Cr Alloys Using Gibbs Free Energy of Mixing and Geometric Methods

Abstract: Thermo-physical properties of these liquid metals, such as heat capacity, thermal conductivity, surface tension, density and viscosity are of particular interest because these properties play important roles in heat and mass transport processes. Knowledge of the viscosities1–7) of pure liquid metals and respective mixtures is important for practical and theoretical purposes. Furthermore, the viscosity of multicomponent8,9) liquid mixtures is an invaluable type of data for the chemical engineer in the design and optimization of industrial processes, particularly for the smelting, casting and welding processes of Fe-based alloys and stainless steels. Therefore, it is very important to obtain a precise and reliable viscosity, especially for high melting point alloys from the industrial point of view. Proposed methods for the measurement of the viscosity include: capillary, oscillating vessel, rotational bob or crucible, oscillating plate, draining vessel, levitation using the damping of surface oscillations and acoustic methods. It is well known that the measurement of the viscosity of molten metals, especially at high temperatures, is difficult because of the reactivity with the crucibles and atmosphere, and also the sensor limitation of the low viscosity. Compilations of the viscosities of pure liquid metals at different temperatures, as well as those of binary liquid mixtures through the whole composition range, Evaluation Model for Viscosity of Fe–Ni–Cr Alloys Using Gibbs Free Energy of Mixing and Geometric Methods

On the relationship between microcanonical and canonical Gibbs distributions

Abstract: It is established that the agreement between the use of microcanonical and canonical Gibbs distributions is possible only if the temperature of a closed equilibrium system and its specific energy in a thermostat are mutually inverse functions. The analysis shows that the derivation of the canonical Gibbs distribution from the microcanoncial does not agree with the physical condition for separating a macroscopic part of a closed equilibrium system.

Wagner interaction coefficients and modified margules equations

Abstract: The relationships between the Wagner interaction and Margules coefficients are derived to discuss their limitations and to clarify incorrect construction of the excess Gibbs energy from the partial excess Gibbs energies, expressed as linear functions of mole fractions. Margules-type equations with Henrian reference states are obtained, and their significance is discussed. An estimate for the Gibbs energy of melting of graphite is obtained, and the use of activity coefficients for deriving the Gibbs energy of melting of refractory elements is suggested. This research is part of the effort in materials properties at the U.S. Bureau of Mines.