Directed free surface energy

When an adsorbing surface is exposed to a gas or vapour adsorption will take place, being accompanied by the absorption or evolution of heat. Such thermal changes have already been noted in the extension and contraction of surface films of liquids. Although the direct determination of the surface energy of solid surfaces presents many experimental difficulties yet of its existence there is no doubt. On the adsorption of a gas or vapour a diminution in the free surface energy of the system likewise occurs. From the Gibbs-Helmholtz relationship dcr... 

One important relationship can be derived directly from Eq. (3.29). For pure liquids we choose the Gibbs dividing plane such that T = 0. Then the surface tension is equal to the free surface energy per unit area ... 

The specific free surface energy of a material is the excess energy per unit area due to the existence of the free surface it is also the thermodynamic work to be done per unit area of surface extension. In liquids the specific free surface energy is also called surface tension, since it is equivalent to a line tension acting in all directions parallel to the surface. 

The system was studied by considering a periodic structure with a finite number of 0 and Al layers (six, and between ten and fourteen, respectively) separated by a vacuum region of 10 A. In the directions parallel to the surface, a periodic structure as that of Figure 20 was used. The relative stability of the different systems was studied through Gibbs free surface energy... 

Given that quantum chemistry calculations directly provide electronic energies, which formally correspond to zero temperature and pressure, ways for connecting to finite, realistic temperature and pressure are needed. One method is first-principles thermodynamics (FPT), the basic concept of which is that the thermodynamically prevailing state of a surface is the one that minimizes the surface free energy, y, subject to external conditions such as temperature and the chemical potentials of the various components of the system ... 

The separation process shown in Fignre 2.35a consists of the formation of two new interfaces, each of nnit cross-sectional area, at a location where no interface previously existed. The free energy change associated with the separation process comes directly from the definition of surface energy [Eq. (2.61)] where two snrfaces of unit surface area are formed. With appropriate assumptions regarding constant temperature, pressure, and incompressible fluids, we can equate this free energy change with the... 

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