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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 17, Number 8
BKCSDE 17(8)
August 20, 1996 

Molecular Dynamics Simulation for Monolayers of Alkyl Thiol Molecules at Air-Solid Interfaces
Song Hi Lee*, Han Soo Kim
We present the results of molecular dynamics simulations of monolayers of long-chain alkyl thiol [S(CH2)15CH3] molecules on an air-solid interface using the extended collapsed atom model for the chain-molecule and a gold surface for the solid surface. Several molecular dynamics simulations have been performed on monolayers with areas per molecule ranging from 18.30 to 32.10 Å2/molecule. It is found that there exist three possible transitions: a continuous transition characterized by a change in molecular configuration without change in lattice structure, a sudden transition characterized by the distinct lattice defects and perfect islands, and a third transition characterized by the appearance of a random, liquid-like state. The analysis of probability distributions of the segments shows that the structure of the chain-molecules at the air-solid interface is completely different from that at the air-water interface in the view of the degree of overlap of the probability distributions of the neighbor segments. The calculated diffusion coefficients of the chain-molecules on the monolayers seem to be not directly related to any one of the three transitions. However, the large diffusion of the molecules enhanced by the increment of the area per molecule may induce the second transition.
700 - 706
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