Theoretical study of the effects of intermolecular interactions in self-assembled long-chain alkanes adsorbed on graphite surface

In this paper, we studied the physisorption of long-chain alkanes CnH2n+2 ( n = 8, 16, 24, 34) on a graphite surface using molecular mechanics simulati ons. The computed results illustrated that the interactions between adsorbe d molecules and substrate are dominated by van der Waals forces whereas the electrostatic interactions are very small. It was found that the ratio of the alkane molecule-molecule interactions (two-dimensional crystallization energy) to the interactions between alkane and graphite (adsorption energy) ranges from similar to2: 5 to 3: 5. The adsorption stability and immobilit y of the alkanes increases proportionally with an increase in the chain len gth. It was concluded that the lateral interactions between adsorbed molecu les are important to the formation of ordered two-dimensional lamellae. The theoretical results support the scanning tunneling microscopy (STM) observ ation of alkylated aromatic compounds on a graphite surface. Copyright (C) 2001 John Wiley & Sons, Ltd.