Melting and freezing of Ar in nanopores

The melting and freezing of Ar condensed into a porous silica matrix (Vycor glass) has been investigated by heat capacity and vapor pressure measurements for various filling fractions and sample histories. A model is proposed which; explains the reduction of the melting temperature, the thermal hysteresis between melting and freezing, and the shape and size of the melting and freezing anomaly in terms of interface melting in a cylindrical geometry. For incomplete fillings, freezing involves delayering transitions in particular of the third monolayer. The first and second monolayer on the pore walls do not participate in freezing and melting.