Elevation/depression mechanism of freezing points of liquid confined in slit nanopores

Abstract

The freezing-point shifts of Lennard–Jones (LJ) particles confined in a parallel slit pore whose size is less than 10 times the diameter of the LJ particle were studied. Using molecular dynamics simulation, the latent heat of freezing, specific volume, wall–liquid interfacial tension and wall–solid interfacial energy were obtained as functions of the slit width. We compare the freezing-point shifts predicted by the Gibbs–Thomson equation to those directly determined by cooling and heating simulations. Although both methods predicted the freezing points elevation in slit pores, the oscillation of the freezing-point shifts observed by molecular dynamics simulations could not be explained by the Gibbs–Thomson equation, even when the dependence of the physical properties on the pore size was considered. By assuming that the intermediate value between the freezing-point shift and the melting-point shift decreases to zero via a power function, the exponent of decay was calculated.