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Diffusion coefficient.

  1. Feb 29, 2008 #1
    [SOLVED] Diffusion coefficient.

    Hi everybody

    I have a Nitrogen atom sitting at the octahedral site in fcc iron. I have calculated the minimum energy path (diffusion path) when moving the Nitrogen atom to the neighboring octahedral site.

    My question is:
    How can i calculate the diffusion coefficient? (only considering the diffusion in that one direction)
  2. jcsd
  3. Feb 29, 2008 #2


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    Hi tkjacobsen, welcome to PF. The standard way is to estimate [itex]D[/itex] for interstitial diffusion is

    [tex]D=\frac{r^2 \nu}{6} \exp\left(\frac{-G_m}{kT}\right)[/tex]

    where [itex]r[/itex] is the distance between sites, [itex]\nu[/itex] is the attempt frequency (the characteristic vibration frequency in the crystal), and [itex]G_m[/itex] is the energy barrier involved in jumping from one interstitial site to another.

    Edit: Sorry, I really should have given a reference. Try Allen and Balluffi's Kinetics of Materials, Porter and Easterling's Phase Transformations in Metals and Alloys, or any good kinetics book.
    Last edited: Feb 29, 2008
  4. Feb 29, 2008 #3
    Thanks alot, this was exactly what I was looking for.

    Best Regards
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