jMol series faceted spheres

Here's a small "twentysix-facet" silicon nanosphere, without surface reconstruction. You can measure its diameter by double-clicking on a pair of atoms. How many atoms does it contain?

We've started to "turn on the red gun" for atoms lying on one of the eight {111} surfaces, the blue gun for atoms lying on one of the six {100} surfaces, and the green gun for atoms lying on one of the twelve {110} surfaces. Many atoms of course lie at the intersection of such surfaces, so they have more than one gun turned on and hence "combination colors" like yellow, cyan, magenta, or white. Atoms on different surfaces have different energies, and are subject to different chemical reactions and surface reconstructions. As a result preferential facets may develop on diamond, silicon or germanium spheres, as well as on voids or "negative crystals" found within these diamond face-centered cubic (and related) solids.

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Polygon models for comparison with the experimental data below are separately available with fifty and seventyfour facets. Larger silicon-atom nanospheres with the same 26 facets mentioned above, plus two bonus facets, are also available with 730 and 3350 atoms.

Cleaved and/or polished diamond-fcc specimens grown under novel experimental conditions might therefore contain voids like those shown in the scanning electron microscope images below. Each void has eight hexagonal {111} faces, six octagonal {001} faces showing concentric straight-edged grooves and a central square pit with 110-type edges, twelve octagonal {011} facets with {023} wings and elliptical marks and/or two bright dots (mounds?) along a line running between adjacent {001} facets, and twenty-four rectangular {113}-type faces which themselves may be segmented into two. The strange patterns or "tattoos" on each type of face were quite unexpected. These, as well as the fractional area of each face, perhaps tell us something interesting about diamond-fcc crystallography under "negative crystal" growth conditions. Can the model above help explain the experimental observations below?

This next figure is a closeup of the center of the image above.

The void above has an {001} face at the bottom, while the void below has a {110} face at the bottom.

Below find an early labeled-schematic of the fifty facets identified at that time.

For the above drawing, a {001} face is at bottom, while below a {110} face is at bottom.