Free energy change melting

Lynden-Bell R M, van Duijneveldt J S and Frenkel D 1993 Free-energy changes on freezing and melting ductile metals Mol. Phys. 80 801-14... 

Further information on the effect of polymer structure on melting points has been obtained by considering the heats and entropies of fusion. The relationship between free energy change AF with change in heat content A// and entropy change A5 at constant temperature is given by the equation... 

Cesium, Cs, and rubidium, Rb, form ideal solutions in the liquid phase, and regular solutions in the solid phase. Their standard state Gibbs free energy changes of melting as a function of temperature, AG c. = (G°cs.l 0,5) and = (G° - G°, 5) respectively, are... 

Let us first consider the liquid-solid phase transformation. At the melting point (or more appropriately, fusion point for a solidification process), liquid and solid are in equilibrium with each other. At equilibrium, we know that the free energy change for the liquid-solid transition must be zero. We can modify Eq. (2.11) for this situation... 

Assuming random mixing in the amorphous lamellae and the melt, the non-combinatorial free energy change per mole of segments on mixing can be written... 

The quantity A/ /L does not involve the translational free energy change of a surfactant molecule since the latter was included in the mixing entropy contribution. The change from an LC crystallized solid to a disordered liquid is considered to occur in two steps the first is from the LC crystallized solid (called below LC solid) to a liquid (called LC liquid), in which the molecules become somewhat disordered but occupy the same surface area Ac and the second step is from the LC liquid to the LE liquid, in which the molecular surface area varies from Ac to Ad- The former is a kind of melting process and has a melting free energy... 

Figure 5.2.2 Plot of Gibbs free energy changes of the thermal reduction (green line) (Fe3(>4 = 3 FeO + 1/2 O2), FeO oxidation (red line) (3 FeO + CO2 = Fe3C>4 + CO), and overall reaction (blue line) (CO2 = CO + 1/2 O2) for the iron-oxide-based cycle. The vertical lines show the melting points of the indicated iron-oxide phases.

The action of a domain in a polymer melt (at constant shear stress) can be shown to be equivalent to the action of a giant crosslink in a rubber. Removing of one crosslink is accompanied by a negative free-energy change (aG2). 

At equilibrium between melt and crystallites, the chemical potential of the melt must be equal to the chemical potential of each crystallite. That is, the free energy change on melting one monomer unit should be equal to the product... 

Here APf is the free energy change on melting a sequence of monomer units from a crystallite of length and... 

Here AFu is the standard free energy change per repeat unit on melting, and ae is the surface free energy change per chain at the ends of the crystallite. It can be shown that the surface free energy associated with lateral surfaces may be ignored in the present case. 

---