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Finding the concentrations of vacancies and interstitials

  1. Dec 12, 2016 #1
    Consider a two-dimensional ionic crystal with a primitive hexagonal lattice. The energy needed to create a Frenkel defect pair is 10eV, and Schottky defect formation costs 8eV.
    Calculate the concentration of vacancies and interstitials in the crystal at 300 K, assuming that all defects are intrinsic.

    n/N=e-(Edef/kbT)
    Where: n = number of defects
    N = number of atoms in the crystal
    Edef = defect creation energy
    kb = Boltzman's constant
    T = temperature

    I've tried using 10eV and 8eV as the defect creation energy however this equals to an answer smaller than *10-100, unsure how to progress.

    Thanks in advance!
     
  2. jcsd
  3. Dec 14, 2016 #2

    mfb

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    2016 Award

    Staff: Mentor

    That is correct. The equilibrium concentration for those defects at room temperature is effectively zero.

    Why do we still have those defects in crystals?
     
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