The molecular dynamics simulations of the melting of a hexane bilayer

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Abstract

Molecular dynamics simulations of a hexane bilayer on the basal-plane surface of graphite have been performed for a number of temperatures, ranging from the solid to the fluid state of the layers, to study the melting behaviour. The molecules are described by a skeletal model, where the interaction sites are represented by an ''anisotropic united atom'' model. At low temperature, the layers form perfectly ordered herringbone structures, which on heating undergo an orientational phase transition to a rectangular-centred structure which is in coexistence with isotropic fluid. The first and second layers subsequently melt at approximately 170 and 190 K, respectively. The features of the transitions are markedly less pronounced for the second layer reflecting the diminishing influence of the surface potential and hence, the higher mobility of the molecules, The melting of the second layer is induced by tilting of the molecules out of the plane and by creating gauche defects. Molecules in the first layer exhibit a smaller tilt and a lower percentage of gauche defects. Compared to a monolayer of full coverage, the presence of the second layer shifts the transition temperatures by similar to 20 K.
Original languageEnglish
JournalSurface Science
Volume347
Issue number1-2
Pages (from-to)169-181
Number of pages13
ISSN0039-6028
DOIs
Publication statusPublished - 1996
Externally publishedYes

Keywords

  • Adsorption kinetics
  • Alkanes
  • Computer simulations
  • Equilibrium thermodynamics and statistical mechanics
  • Graphite
  • Molecular dynamics
  • Surface melting
  • Surface thermodynamics

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