Phase separation
Entry by Emily Redston, AP 225, Fall 2011
We typically talk about phase separation in terms of the regular solution model of liquids. The free energy of mixing can be written as,
<math>\frac{G_{mix}}{kT}=Nnv _{A}\ln v _{A}+x _{B}\ln v _{B}+\epsilon v _{A} v _{B}</math>
where <math>\epsilon = zN[V_{AB} - {1 \over 2}(V_{BB}+V_{BB})]</math>
<math>V</math> represents bond energies, <math>z</math> is the number of neighbors, <math>N</math> is the total number of atoms, and <math>x</math> is the mole fraction. The sign of <math>/epsilon</math> is essential in determining the solution's behavior as a function of temperature. If <math>/epsilon</math> then the change in free energy upon mixing is always negative, so the atoms will always want to be fully mixed. If <math>/epsilon</math>, then mixing or phase separation can occur depending on the temperature.
See also:
Phase separation in Phases and Phase Diagrams from Lectures for AP225.
References
The Role of Polymer Polydispersity in Phase Separation and Gelation in Colloid−Polymer Mixtures