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Homework Help: Lattice parameter + valence + avg time between collisions

  1. Sep 25, 2011 #1
    valence Z=1, lattice param a = 4.05 conductivity = 1.76e7 . What's the avg time between collisions of a conduction electron in this metal (bcc structure).

    really have no idea lol
    Last edited: Sep 25, 2011
  2. jcsd
  3. Sep 25, 2011 #2
    The equation I think I got to use is : [itex]\tau[/itex]=([itex]\sigma[/itex]*m)/ (n*e^2)

    n= 2.52 e28 sigma = 2.38e7 and I'm guessing e = 1.6e-19 but i got the wrong answer.
  4. Sep 25, 2011 #3
    How did you get the value for n? It seems that you have an error there.
  5. Sep 25, 2011 #4
    Since the crystal structure of Na is bcc, there are two Na atoms in each conventional unit cell of volume a^3. Denisty n= 2/a^3... so 2/(4.3e-10)^3=2.52e28
  6. Sep 26, 2011 #5
    In the original post you said that the lattice constant is 4.05A (and not 4.3).
    Which one is it?
  7. Sep 26, 2011 #6
    ah sorry. in the example problem it's 4.3 but in the homework problem it's 4.05
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