Physics – Condensed Matter – Soft Condensed Matter
Scientific paper
2005-05-26
Phys. Rev. B 73, 085422 (2006)
Physics
Condensed Matter
Soft Condensed Matter
Scientific paper
We present the results of molecular dynamics (MD) studies of hexane physisorbed onto graphite for eight coverages in the range $0.875 \le \rho \le 1.05$ (in units of monolayers). At low temperatures the adsorbate molecules form a uniaxially incommensurate herringbone (UI-HB) solid. At high coverages the solid consists of adsorbate molecules that are primarily rolled on their side perpen-dicular to the surface of the substrate. As the coverage is decreased, the amount of molecular rolling diminishes until $\rho$ = 0.933 where it disappears (molecules become primarily parallel to the surface). If the density is decreased enough, vacancies appear. As the temperature is increased we observe a three-phase regime for $\rho > 0.933$ (with an orientationally ordered nematic mesophase), for lower coverages the system melts directly to the disordered (and isotropic) liquid phase. The solid-nematic transition temperature is very sensitive to coverage whereas the melting temperature is quite insensitive to it, except for at low coverages where increased in-plane space and ultimately vacancies soften the solid phase and lower the melting temperature. Our results signal the importance of molecular rolling and tilting (which result from an the competition between molecule-molecule and molecule-substrate interactions) for the formation of the intermediate phase, while the insensitivity of the system's melting temperature to changing density is understood in terms of in-plane space occupation through rolling. Comparisons and contrasts with experimental results are discussed.
Pint Cary L.
Roth Michael W.
Wexler Carlos
No associations
LandOfFree
On the Behavior of Hexane on Graphite at Near-Monolayer Densities does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with On the Behavior of Hexane on Graphite at Near-Monolayer Densities, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the Behavior of Hexane on Graphite at Near-Monolayer Densities will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-522516