# Molecular Dynamics of an Atomic System

SC '97, San Jose, CA

Ken Flurchick*, Mark Reed** and Theresa L. Windus*+
*Ohio Supercomputer Center |  | **North Carolina Supercomputing Center |  | +Aeronautical Systems Center
OSC |  | NCSC |  | MSRC PET
1224 Kinnear Rd. |  | 3021 Cornwallis Rd. |  | 2435 Fifth Street, Bldg. 676
Columbus, OH 43212 |  | RTP, NC 27709 |  | WPAFB, OH 45433

The IMMERSADESK© Molecular Dynamics (IMD) application code was developed as a module for the Application Visualization System (AVS) from Advanced Visual Systems, Inc. was ported to the IMMERSADESK© from Pyramid Systems, Inc. at the Aeronautical Systems Center (ASC) as part of the Ohio Supercomputer Center activities Programming Environment and Training - Computational Chemistry and Materials (CCM) support.

The IMD application displays the results from a molecular dynamics (MD) simulation. This simulation consists of spherically symmetric, electrically neutral atom system interacting via a Lennard-Jones potential. The atoms are displayed as spheres, colored by the magnitude of the velocity. (Red being the fastest and blue being the slowest).

## Figure 1 Molecular Dynamics display.

In the display, streamers are shown to give information about the path of the particles. The tails are also color coded by the magnitude of the velocity to include velocity history information. The MD simulation was part of the research done to compute the thermal transport coefficients of a moderately dense gas, in which:

- the molecular dynamics technique is used to trace the evolution of the system through phase space.
- microscopic position and velocity information is then used to construct thermodynamic properties such as the virial, and the thermal transport coefficients.
- the simulations in this work use the Lennard-Jones interaction potential.

For additional information, see
Mark S.C. Reed and K.M. Flurchick, "Hybrid Molecular Dynamics: An Approach to Low Density Simulations", Computer Physics Communications 81, 56, (1994).

The IMMERSADESK/CAVE© provides a unique way to visualize particle dynamics and behavior such as clustering as well as gather spatial relational information. For the clustering one can view:

- cluster formation
- propagation
- transport
- aggregation
- destruction

In this visualization, one can view collision dynamics plus spatial and momentum shifts by carefully watching the tails and the color changes.

## Figure 2 Molecular Dynamics display.