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Homework Help: Distribution of electrons below the Fermi energy

  1. Dec 7, 2007 #1
    I feel dumb that I can't figure this out. I'm sure its something simple that I'm just not seeing, but its really frustrating.

    1. The problem statement, all variables and given/known data
    How many electrons (in percent of the total number of electrons per mole) lie KbT (ev) below the Fermi energy? Take Ef=5eV and T=300K

    2. Relevant equations
    Not quite sure, since the Fermi function did not work.


    3. The attempt at a solution
    I tried using the Fermi function and end up with values around 30%. The answer (from the back of the book) is [tex]\Delta[/tex]N/Ntot=.566%

    Any ideas ?

    Thanks!
     
  2. jcsd
  3. Dec 7, 2007 #2
    Since Ef is much larger than kT, you wouldn't expect 30% of the electrons to lie between Ef-kT and Ef, right? You'd expect a much smaller fraction, like the answer from the book.

    When you integrated the Fermi function to get [tex]\Delta[/tex]N and Ntot, what were the energy boundaries of your integrals?
     
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