(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I'm trying to figure out the lattice parameter, c, of the HCP crystal structure.

Here are a couple links showing the structure: http://images.google.com/imgres?img...agonal+close+packed&hl=en&safe=off&sa=N&um=1"

2. Relevant equations

I know that a=2r, where r is the atomic radius of whatever atoms make up the structure. I'm not really sure what else is relevant, it seems to be a problem of geometry and I'm having trouble working it out.

3. The attempt at a solution

I can't really type out my math that I've attempted to do since I am having trouble conceptually. I think that the way to go about doing it is with a triangular pyramid, since with the way that the atoms sit on top of each other you will get an equilateral triangle as your base (sides=a) and then the height is c/2. However I can't seem to get this to work out mathematically. I got c to be 2*sqrt(3)*r, which is incorrect.

Thanks for the help.

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Lattice Parameter c of HCP

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