Evolution criterion in nonequilibrium and a variational principle for equilibrium states of free-standing liquid crystalline films

摘要

Starting out with the thermodynamic balance equations of liquid crystalline films and the second law of thermodynamics, an analog to the global surface free energy is derived whose time derivative is negative definite out of equilibrium and zero in equilibrium. This evolution criterion allows one to formulate a variational principle for the equilibrium states by minimizing the modified global surface free energy derived above. Thus the quantity which is extremal in equilibrium in the case of free-standing crystalline films is not presupposed ad hoc, but derived from an evolution criterion based on the second law.