Molecular simulation of melting in tetracosane (C24H50) monolayers and bilayers on graphite

Cary Pint

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arXiv · cond-mat/0602478

Molecular simulation of melting in tetracosane (C24H50) monolayers and bilayers on graphite

Cary Pint

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Abstract

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.

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Cary Pint. 2006-02-21. Molecular simulation of melting in tetracosane (C24H50) monolayers and bilayers on graphite. https://arxiv.org/abs/cond-mat/0602478

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