Wikipedia:Featured picture candidates/Close-packed spheres

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Close-packed spheres[edit]

When many of the chemical elements, such as the noble gases and platinum-group metals, freeze to a solid — the most ordered state of matter — their crystal structures have a closest-packed arrangement. This yields the greatest possible packing density and the lowest energy state.

— — Below is a candidate caption for use in Close-packing article, added 16:33, 26 February 2007 (and revised 20:15, 26 February 2007) — —

Shown above is what the science of sphere packing calls a closest-packed arrangement. Specifically, this is the cannonball arrangement or cannonball stack. Per the Kepler conjecture, no other arrangement of spheres can exceed its packing density of 74.048%. The cannonball stack shown above (which takes the form of a regular tetrahedron) has a face-centered cubic lattice. Note how the two balls facing the viewer in the second tier from the top contact the same ball in the tier below. This does not occur in hexagonal close-packing.
Reason
It’s a ray-traced CAD image that I think is attractive and informative
Articles this image appears in
Thermodynamic temperature
Close-packing (added 02:41, 1 March 2007)
Creator
Greg L
Nominator
Greg L
  • Support Throwing it out there and seeing if others like it too. Greg L / (talk) 07:07, 26 February 2007 (UTC)[reply]
  • comment it doesn't seem to illustrate thermodynamic temperature as well as other images on that page. I would like to see it as an illustration of close-packing though. Debivort 08:23, 26 February 2007 (UTC)[reply]
  • Comment. Is it really many chemical elements that form close packed structures? The reflecting balls sure are eye-candy, but I'm not entirely convinced that this is the most clear illustration. And what about the two possible stacking orders? --Dschwen 09:31, 26 February 2007 (UTC)[reply]
    • Comment (answer) Many. Roughly 43 at room temperature. More at absolute zero. There isn't any consistency among sources though. For instance Wikipedia and WebElements differ. Greg L 17:07, 26 February 2007 (UTC)[reply]
    • This would better illustrate Close-packing rather than Thermodynamic temperature, but Close-packing already has a great clean diagram. --Dschwen 09:33, 26 February 2007 (UTC)[reply]
      • Comment (response) I agree. The Close-packing article could benefit from a 3D illustration of close-packed spheres; not everyone can easily or quickly grasp the 2D illustration that's already there. But what's already there is pretty good so it will take some effort to add this without redundancy. I have a bit more studying to do on the subject before interjecting this into that article. I've got both my crystalograhy/mineral books out. One could also add it to the talk page and let someone more expert in the subject move it to the article (as I had done with this picture of the sun). The first sentence of the newly added caption wouldn’t appear in the caption in its actual placement. Greg L 17:07, 26 February 2007 (UTC)[reply]
        • the caption says fcc but the image shows hcp. --Dschwen 19:30, 26 February 2007 (UTC)[reply]
          • Three-face + base (tetrahedral) pyramidal cube packing is definetely FCC. HCP is an entirely different arrangement (starting at the third tier down). Notice how the two balls facing the viewer, in the second tier down, both touch the same ball in the third tier down. That doesn’t happen in HCP. I revised the alternative caption with this explanation. Greg L 19:40, 26 February 2007 (UTC)[reply]
            • Sorry, my bad, you are right, I had it twisted up in my mind. --Dschwen 21:54, 26 February 2007 (UTC)[reply]
              • Visualizing 3D sphere packing is tough. Exercises like Featured picture candidates seems to be a good venue for fine-tuning captions. As now revised, confusion will hopefully be infrequent. Greg L 22:13, 26 February 2007 (UTC)[reply]
  • Opppose. Very good for a helper pic in the article, but not really FP material. There's just not enough content --frothT 04:52, 27 February 2007 (UTC)[reply]
  • Comment / Update I've added the illustration to the Close-packing article. I think the illustration makes understanding 3D sphere packing much easier. Greg L 20:47, 2 March 2007 (UTC)[reply]
  • Support Tomer T 20:52, 4 March 2007 (UTC)[reply]

Not promoted MER-C 08:48, 7 March 2007 (UTC)[reply]

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