Advanced Topics on Condensed Matter Physics
Department of Physics, NCU
THEORETICAL STUDIES OF THE COLLOIDAL DOMAINS OF PHASES IN COEXISTENCE
Speaker
Prof. S. K. Lai
Complex Liquids Laboratory
Department of Physics, National Central University
Date 2016/10/27 (Thur)
Time: 14.00
Place: S4-625
Experimentally, the study of the phase diagrams of a colloidal dispersion starts with a given initial concentration of colloids which is prescribed at given temperature (usually for uncharged colloids), or an electrolyte concentration (for charged colloids). This is in marked contrast to the theoretical means where one applies the thermodynamic equilibrium conditions of equal pressure and equal chemical potential to locate the boundaries of coexisting phases. Thus, theoretically, one is in fact effecting a “confirmation” of known experimental domains of phases in coexistence and the boundaries of coexisting phases are the main results of calculations. The present work puts forth the idea of free energy minimization to study phase diagrams of coexisting phases and the calculated results are in the same spirit as those done in colloidal experiments. In addition to crosshatch the domains of phase separation, the theory yields naturally the volumes occupied by the subsystems in coexistence. The branches of the coexisting phases is merely the by-products of the calculations. As concrete illustrations, we study the microgel dispersion (uncharged colloids) and the disc-colloid mixture (two-component uncharged colloids). The basic ideas and the elegance of the methodology are clearly manifested in these two systems.