NITROGEN ON GRAPHITE
 
Researchers at Southampton University are studying the adsorption
of small molecules on a graphite surface by computer simulation.
The current project concerns nitrogen molecules which adsorb onto
graphite to form a variety of phases, depending upon temperature
and the number of molecules present.
The Chemistry Dept at the University has developed a complex set
of programs which solve Newton's Laws for the molecular interactions
involved. A raw data tape containing the coordinates and the
directions of motion for each nitrogen was given to the UKSC with
the aim of producing a graphical representation of the data.
 
We have 1000 frames of simulation data for each of two temperatures.
The movie being shown contains 300 frames (determined by the size of
the memory in our 5085). There are 98 nitrogens, each represented
by a single coloured vector. They are bounded by a cyan box.
The regular hexagonal arrangement of magenta dots represents the
carbon atoms in the graphite surface. The initial view looks down
on the graphite surface and shows the fairly random motion of the
nitrogens. This movie simulates the motion at 40K. 50 frames of
movie data correspond to 1 pico-second of real action.
If the dials are used to transform the movie about the x-axis
the random motion of the molecules out of the plane of the surface
can be observed. If the movie is viewed at right-angles to the
surface the coincident cyan lines represent the plane which passes
through the centres of the carbon atoms in the surface.
The general motion of the nitrogens is very complicated and analysis
is best done by identifying some specific examples of interesting
motion and examining these in more detail.