Vant Hoff isotherm

Since the formation constants are easily accessible in chemistry, the standard vant Hoff isotherm transforms Eq. (80) into Eq. (81), whereby is often referred to as the Boltzmann factor of intermetallic interaction (Koper and Borkovec, 2001). 

Regrouping the absolute intermolecular affinities followed by application of tibe standard vant Hoff isotherm eventually leads to Eq. (99), which is known as Ercolani s model (Ercolani, 2003 Hamacek et al., 2006). 

The relationship between the change in free energy AG and the equilibrium constant K is given by the vant Hoff isotherm... 

Desorption isotherms for the hydrides of LaNi eAlo,] and LaNij sAlo.s are presented and values for the enthalpy and entropy changes of the hydriding reactions are calculated from the vant Hoff plots of log P vs, i/T. A crystallographic model of LaNij Al is shown and consideration of the nearest neighbor atom distribution leads to a rationalization of the observed linear relationship between the enthalpy change, aH, and the aluminum composition. Brief discussions of methods to predict dissociation pressures or interstitial site occupation are included. The cubic and hexagonal ABs phases are compared and, finally, the application of these alloys in chemical heat pump systems is noted. 

Co is the concentration defining the standard state by convention, Co = 1 mol. If Xd has been measured as a function of temperature, AH and A5d can be derived from its temperature dependence by applying the Vant Hoff law. In recent years, isothermal titration microcalorimetry (ITC) has also been used for that purpose. As reviewed by Fisher and Singh (1995) and Ladbury and Chowdhry (1996), microcalorimetry gives direct access to AH and, also, if the titration is performed at several temperatures, to the heat capacity change AGd at constant pressure. The first quantity is proportional to the heat evolved on mixing known amounts of the two components of a complex, and the latter is equal to... 

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