Summary

An animation of HCP lattice building. The black circles are the first "plane" of spheres. The blue line represents ${\displaystyle 2r}$. The red triangle is an equilateral triangle with sides of ${\displaystyle 2r}$. The next red shape is a regular tetrahedron with sides of ${\displaystyle 2r}$.

Licensing

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Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

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	Attribution: I, Jonathunder
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Attribution: I, Jonathunder

You are free:

• to share – to copy, distribute and transmit the work
• to remix – to adapt the work

Under the following conditions:

• attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
• share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.

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upload from http://en.wikipedia.org/wiki/Image:Animated-HCP-Lattice.gif