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potfit

Examples (old)

The Hopping Ball

hopping ball

A tiny sphere bumps into a thin plate of only two atomic layers. Sphere and plate are modeled as fcc solids with atoms of different types. Atoms of the same type interact via attractive LJ potentials, whereas atoms of different type repel each other (see figure). Moreover the plate's atoms have a ten times larger mass than those of the sphere. Periodic boundary conditions are employed.

potential function

The ball bounces off the upper side of the plate, leaves the box through the top and re-enters from below via the PBC. It then bounces off lower side of the plate, and the process is started over again.

This (and larger versions of this simulation) are mainly done to see if the code works correctly on parallel machines. One can check if the particles are handed over correctly from CPU to CPU. It's also great fun to watch the resulting movies.

Cracks Propagating in a 2d Quasicrystal

crack in a quasicrystal

The picture above shows a crack moving through a twodimensional quasicrystal. The whole sample consists of roughly 120000 atoms, only a part of which are shown. A dislocation has travelled from the crack tip down to the lower right. This generated a stacking fault (phason wall), which is clearly visible in the image. The simulation was run on 32 nodes of an Intel Paragon.

another crack in a quasicrystal

The image above shows another crack in a 2d quasicrystal. The colors represent kinetic energy. This simulation was run on 64 nodes of an Cray T3E and took only about 30 minutes.