1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Diamond Lattice Question

  1. Jan 16, 2009 #1

    I dont get the solution to the following question so I am hoping someone can explain!

    Ok so, the question is we have Silicon, which I have read has a DIAMOND LATTICE structure.
    Which basically seems to mean two face centered cubes come together. Now I need to calculate the VOLUME DENSITY of ATOMS. I know the lattice constant ex. 5.4 x 10^-10 m

    Now From my knowledge: fcc in 3d has 1/8th of an atom on each of the 8 corners of the cube. And has also has 1/2 of a atom on each of the 6 faces. That makes a total of

    1/8*8 = 1
    1/2*6 = 3
    4 atoms in total

    Now the solution says there are somehow 8 atoms. Im assuming there are 8 because it is a diamond lattice structure and so there are 2 cubes meaning 4 x 2 = 8 atoms..first is this assumption correct?

    if that is correct then when they calculate the volume they use

    (5.4 x 10^-10)^3 = I THOUGHT THIS WAS THE VOLUME OF ONLY ONE CUBE....:O..

    answer somehow is

    atom density = 8/ (5.4 x 10^-10)^3


    why did they use 8 atoms and why did they use that volume for only one cube if the 8 atoms come from fcc cubes!!!

    please help!
  2. jcsd
  3. Jan 18, 2009 #2
    ok i figured it out after some research ..
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook