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To: chemistry@www.ccl.net
From: underhil@me2.rmc.ca (Ross Underhill)
Subject: Simulating the effect of liquids and gases on films


I'm interested in examining the structure and self-assembly of multilayer
films using molecular mechanics.  Unfortunately, the structure of these
films - often their existance - depends on the presence of a liquid or gas
medium which helps to hold the film onto the substrate even if it is not
incorporated into the film.  A trivial example would be Langmuir-Blodget
films of stearic acid on aluminum.  In air a multilayer film is stable for
months.  When the sample is introduced to vacuum, all but the layer directly
attached to the aluminum rapidly sublimate from the surface.  

To study the self assembly of a monolayer film at the solid-liquid interface
one properly needs to incorporate the liquid itself.  However, the inclusion
of the liquid molecules rapidly drives the computational effort through the
roof.  It seems to me that it ought to be possible to simulate the effect of
the liquid by a viscous damping term, possibly only applied to atoms on the
solvent accessible surface of a molecule.  Has anyone looked at handling
this problem in this kind of way or have any comments to make on whether
they think this kind of approach would be feasible?

Dr. Ross Underhill
Royal Military College of Canada
Kingston, Ontario
K7K 5L0
(613) 541-6000 X6175