Molecular Dynamics study of tetracosane monolayers adsorbed on graphite

We present the results of Molecular Dynamics (MD) simulations of tetracosane (C$_{24}$H$_{50})$ monolayers physisorbed on graphite. C$_{24}$H$_{50}$ molecules have explicit hydrogens and the graphite is represented by six graphene layers. We focus our analysis on the microscopic mechanism of melting, experimentally observed at $T$ = 340 K. We are looking for the pre-melting transformations with emphasis on the correlation between translational disordering of molecules and their internal degrees of freedom. We analyze several order parameters and their fluctuations along the MD trajectories. We show that the all atom representation of C$_{24}$H$_{50}$ is much more sensitive to the model of intramolecular interactions than united atom model. Footprint reduction during melting involves a simultaneous loss of intramolecular and translational order.