I cannot understand how a diamond lattice can have eight atoms/unit cell.

Best site I found to describe it:
http://ece-www.colorado.edu/~bart/book/boo..._2.htm#fig2_2_5

I can see 18 atoms per lattice unit and five atoms per unit cell. I don't know how they come up with eight. Anyone?

ok, i havent take chem in forever but heres my best shot...

Look at the sinlge cube latice, there is an atom in each corner. But only 1/8 of each of those atoms are actually in the unti cell. So there is really only a total of one atom in the entire cell.

A diamond lattice has atoms at each corner as well as each face. In addition, there are four atoms fully within the unit to create the tetrahedral shape that makes the diamond lattice. Thus..

8 atoms in corner, only an 1/8 in = 1
6 atoms on faces, only a 1/2 in = 3
and four atoms fully inside = 4

Total of 8 atoms per unit cell!

This post has been edited by orvillescelica: Jan 18, 2005 - 1:33 AM