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Statistical mechanics average energy

  1. Mar 20, 2008 #1
    1. The problem statement, all variables and given/known data

    average energy per particle u = (Eo + E1 e^(-B deltaE)) / (1 + e^(-B deltaE))
    B = 1/T

    2. Relevant equations

    Possibly relevant: e^x = 1 + x^2 / 2! + x^3 / 3! ......

    3. The attempt at a solution

    It tells me the average energy is about u = Eo + (deltaE)e^(-B delatE) as t approaches 0, and u = (1/2)(Eo + E1) - (1/4)B(delataE)^2 as T approaches infinity.

    I can easily derive the first term in both of these equations, but the second is giving me some trouble. I tried to Taylor expand the exponential, but everything seems to cancel out and appear as before.
  2. jcsd
  3. Mar 20, 2008 #2


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    What is the question???
  4. Mar 20, 2008 #3
    Sorry, I am attempting to derive the solution that was given to me, the energy as T approaches 0 and infinity from the average energy per particle
  5. Mar 20, 2008 #4


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    You might want to try the T-> infinity first. I got their answer. Just Taylor expand. And you will also need to use that

    [tex]\frac{1}{1+x} \approx 1-x [/tex]

    If you don't get it, post your steps
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