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Why is diamond structure not bravais lattice? Is it because of interpretation of two f.c.c. structures?

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Diamond structure is a FCC bravais lattice with two carbon atoms per site. As the OP says, it is like two FCC lattices with the second lattice shifted by (1/4, 1/4, 1/4) in reduced coordinates from the first one.

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  • $\begingroup$ Diamond structure is bravais lattice? $\endgroup$ – Ka Sikh May 15 '17 at 6:39
  • $\begingroup$ No, it is a combination of a FCC bravais lattice and a two carbon atom basis. This means that at each point of the bravais lattice, there is two carbon atoms placed exactly the same at each point. Those two atoms are shifted as I said in the answer. $\endgroup$ – fgoudra May 15 '17 at 14:37
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Is it because of interpretation of two f.c.c. structures ?

Yes, and consequently the atoms don't all have an identical environment.

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  • $\begingroup$ Why is NaCl a bravais lattice? $\endgroup$ – Ka Sikh May 14 '17 at 16:04
  • $\begingroup$ I think the origin lattice point of two FCC lattice makes the difference. In NaCl , If Na is located at (0,0,0) then Cl is located at (1/2,1/2,1/2). While in diamond structure, two origins are (0,0,0) and (1/4,1/4,1/4). $\endgroup$ – Ka Sikh May 14 '17 at 16:12
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    $\begingroup$ @KaSikh - why do you think NaCl is a bravais lattice? $\endgroup$ – Jon Custer May 14 '17 at 17:31
  • $\begingroup$ @jon custer-Is it not? I think I misunderstood what's written in my book. $\endgroup$ – Ka Sikh May 14 '17 at 17:39
  • $\begingroup$ @KaSikh - no, it is an fcc lattice with a two atom basi. $\endgroup$ – Jon Custer May 14 '17 at 18:12

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