jMol series faceted spheres (large)


Here's a larger "twentyeight-facet" silicon nanosphere with 730 atoms and no surface reconstruction. You can measure its diameter by double-clicking on a pair of atoms. There are six {001} facets characterized by zig-zag dimer backbones, eight {111} facets characterized by bonds directed vertically up or down from the surface, and twelve {110} facets characterized by a truncated ridge-valley structure. Can you recognize examples of each, e.g. visible in profile view when looking down a set of {011} tunnels in the lattice? There are also two bonus facets, namely a (131) and a (320) facet. Can you find them? Hint: The green and magenta highlights might help, and the applet menu will let you turn on cartesian coordinate axes as well. What zone is perpendicular to these two facets? Do the the atom terminations at these facets provide clues to the defect structure associated with the {113} and {320} "transition facets" in the experimental images below? Would larger models of such surfaces help?

Polygonal models for comparison with the experimental data below are separately available with fifty and seventyfour facets. A 3350-atom sphere with the same facets (to allow a better look at surface atom configurations) is also available here.


Cleaved and/or polished diamond-fcc specimens grown under novel experimental conditions might therefore contain voids like those shown in the digital 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?

Below 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.