Dependence of quasiliquid thickness on the liquid activity: A bulk thermodynamic theory of the interface

Studies of the phenomenon of quasiliquid formation span systems as diverse as noble gases, complex organic molecules, and metals, and span triple point temperatures from 25 to 933 K. We show that when viewed as a single phenomenon essentially all published measurements of the quasiliquid layer thickness on solids below the melting point can be plotted as a function of the thermodynamic activity. Two classes of behavior are then observed: one for molecular systems and one for atomic systems. We derive a dependence on activity through a grand canonical lattice gas calculation. This is the only such unifying theory of this phenomenon.