Molecular dynamics simulation of surface ordering in liquid n-alkanes

Anomalous structures were recently found at the liquid-vapor interfaces in n-alkanes, n-alcohols, etc. In this paper, detailed surface structure of the liquid n-alkane is investigated by molecular dynamics simulation. The computation is considerably accelerated by use of a simplified molecular model, in which detailed molecular structures of hydrocarbons are neglected; the systematic investigation of the melting and freezing of relatively large system is thereby enabled. Around the bulk melting point, an appreciable ordered monolayer is observed at the liquid-vapor interface. The momolayer is characterized by the preferred bond orientation perpendicular to the surface normal and the accumulation of the chain ends at the surface.