Melting mechanism in monolayers of flexible rod-shaped molecules

URL:http://link.aps.org/doi/10.1103/PhysRevLett.69.652 DOI:10.1103/PhysRevLett.69.652The melting of butane and hexane monolayers adsorbed on a graphite basal-plane surface has been studied by molecular-dynamics simulations and experimentally by neutron diffraction. The simulation results are qualitatively consistent with the observed diffraction patterns and suggest a general mechanism for melting in monolayers of flexible rod-shaped molecules. Melting requires the formation of vacancies in the monolayer by molecular motion perpendicular to the surface. This ''footprint reduction'' mechanism implies that strictly two-dimensional theories of melting are inapplicable to these systems.This work was supported by Danish Natural Science Research Council Grant No. M 11-7015, U.S. NSF Grants No. DMR-8704938 and No. DMR-9011069, and Pittsburgh Supercomputing Center Grant No. DMR-880008P