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| Molecular Dynamics Simulation | |
Since the late 1970s, researchers in the
School of Physics
have developed and used novel theoretical and computer-based
modeling and simulation methods to investigate the microscopic
origins of complex physical and chemical materials phenomena.
These methods, known as molecular dynamics simulations, yield
insights into the microscopic nature of structure and dynamics in
various materials systems. These systems range from atomic
processes underlying friction, lubrication and wear, and the
size-dependent evolution of the properties of materials clusters,
to the formation mechanisms of nanometer-scale wires and quantum
dots, and the quantized electronic conductance in such
miniaturized structures.
In a 1990 report in Science, the researchers predicted the
formation and properties of metallic nanowires, generated through
elongation of the contact between the tip of a scanning tunneling
probe and a gold surface. This study showed that mechanical and
electrical properties of such wires vary significantly as their
width narrows to the nanoscale — less than a few atoms.
The
information is relevant to the fabrication of novel miniaturized
electronic devices, and it led to a joint study between Georgia
Tech researchers and an experimental group in Madrid. The
researchers reported in a 1995 Science article that they produced
such wires in the laboratory, and measured room-temperature,
quantized electronic transport through them. The study verified
the scientists' early theoretical predictions.
Also in 1995, the Georgia Tech researchers reported in Science
that under extreme conditions, lubricants in systems such as
computer disk drives may behave in unexpected ways that can harm
the systems they are intended to protect. Molecular dynamics
simulations predicted that ultra-thin films of organic lubricants
used in nanometer-scale devices may act more like solids than
liquids when subjected to high pressures.
In 1998, they reported in the Journal of Physical Chemistry
that rapidly oscillating the width of the lubricant-filled gap
separating two sliding surfaces can significantly reduce friction
between them. The technique keeps the lubricant in a state of
dynamic disorder, preventing the formation of molecular layering
that can increase friction. Based on molecular dynamics
simulations, the findings would be of particular interest to
designers of micro-scale machines.
The research program is headed by Dr. Uzi Landman, director of
the Center for Computational Materials Science, and a Regents'
and Callaway Chair professor of physics. His Georgia Tech
collaborators include R.N. Barnett, E.N. Bogachek, C.L.
Cleveland, J. Gao, W.D. Luedtke, A.G. Scherbakov and C.
Yannouleas.
Courtesy of Dr. Uzi Landman
This molecular dynamics simulation represents the formation
of a metallic nanowire, generated as a slightly indented nickel
tip (with atoms depicted as red
spheres), as it is pulled away from a gold surface (with the top
atomic layer of the gold substrate depicted by yellow spheres,
the second layer down by blue spheres, and so on).
For more information, contact Dr. Uzi Landman, School of Physics,
Georgia Tech, Atlanta, GA 30332-0430. (Telephone: 404-894-3368) (Email:
uzi.landman@physics.gatech.edu)
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