  This work reports an investigation into the solid phase behavior and melting
behavior of tetracosane (C24H50) monolayers and bilayers physisorbed onto the
graphite basal plane using molecular dynamics simulations performed in the
constant (N,V,T) ensemble. This study is conducted in order to perform an
in-depth analysis of the melting process in the quasi-2D monolayer, and compare
the molecular behavior in the monolayer and the bilayer at temperatures near
and at the melting transition. The bilayer is studied by looking at quantities
for the bottom and top layer separately in order to break apart the evolution
of differing structural and molecular properties that are normally associated
with melting in the monolayer. Simulations suggest that the melting temperature
in the bilayer is increased significantly from that of the monolayer- which
already occurs at temperatures higher than the bulk tetracosane melting
temperature. In addition, a layer-by-layer melting effect is observed where
significant factors associated with the melting transition- the formation of
molecular gauche defects and the perpendicular rolling of the molecule chains-
occur in the top layer of the bilayer at significantly lower temperatures than
they occur in the bottom layer. Variations are conducted to better understand
the role of different interactions in melting of the crystalline monolayer, and
the results of simulations are discussed in comparison to recent STM and
diffraction experiment and found to be in good agreement.
