Glass Transition, Crystallization, Melting, and Decomposition of Nanoconfined Propane Films at Cryogenic Temperatures

Abstract

This study investigated translational diffusion of propane in thin films at cryogenic temperatures to elucidate crystallization and premelting of nanoconfined systems. The propane crystallizes on a Ni(111) substrate at around 48 K, but mobile molecules evolve on the surface immediately after crystallization, as revealed from their permeation through pores and gradual change in film morphology up to 80 K. The liquidlike behavior is attributable to surface premelting of crystallites. The crystallites become larger via surface diffusion, but the premelting layer thickness does not change over a wide temperature range. The crystal cores start to melt at 5 K below the bulk melting point, at which temperature the melting layer thickness increases dramatically. This behavior is consistent with the surface melting of macroscopic systems. Liquidlike propane molecules decompose at the interface of a deoxygenated V substrate during crystallization and premelting, as revealed from methane desorption via C–C bond trun...