The structure, dynamics, and properties of materials are governed by microscopic-level interactions and processes. Basic understanding of material processes requires knowledge of the underlying energetics and the fundamental interaction, transport, growth, and transformation mechanisms on a refined level.
Research in the Center for Computational Materials Science (CCMS) focuses on the development of analytical models and novel computer-based classical and quantum molecular dynamics simulations for investigations of a wide range of condensed matter phenomena, such as the following: equilibrium structure and the dynamics of solid surfaces, equilibrium and nonequilibrium growth processes at solid-liquid interfaces and phase transformations, epitaxy and melting; heterogeneous (surface) reaction dynamics; the formation and properties of glasses; surface diffusion; atomic-scale friction and lubrication; confined complex fluids; electron localization and excitation dynamics of small clusters; and the dynamics of cluster fission.
Molecular Dynamic Simulations : A New Strategy for Reducing Friction in Mechanical Devices
Jianping Gao, researcher in CCMS, has been using the IHPCL Pentium II cluster for molecular dynamics simulations. These simulations help in the atomic-scale study of thin-film lubricants. It is hoped that this work will help improving the chemical composition of lubricants used to separate mechanical moving parts. Physics researchers at the Georgia Institute of Technology report in the June 25 Journal of Physical Chemistry (Vol. B102, pp.5033-5037 (1998)) that by rapidly oscillating the width of the lubricant-filled gap separating two sliding surfaces, they can significantly reduce friction between them. This 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 builds on earlier studies showing that thin-film lubricant molecules confined between two solid surfaces organize themselves into well-ordered layers. In a confined film of approximately 20 Angstroms, a lubricant such as hexadecane forms 4-5 layers in which the long-chain molecules all lie parallel to the sliding plane.
We have completed preliminary investigation and simulation. The graph below shows the orientation of the molecules in X and Y directions with height specifications in the Z directions. The cluster formation of molecules is helpful in determining whether a new surface of molecules will exist adding to frictions.
