Potassium chloride (KCl) has a Schottky pair formation energy

PHYSICS · Subjective · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Crystal structure, bonding and diffraction · Crystal structure, bonding and diffraction

Solid State Physics, Ch Point defects, dislocations and alloys

Problem

Potassium chloride (KCl) has a Schottky pair formation energy ES=2.6 eVE_S = 2.6\,\mathrm{eV}. With charge neutrality imposed before the free energy is minimised, the equilibrium fraction of sites carrying a vacancy is n/N=e−ES/2kBTn/N = e^{-E_S/2k_BT} (the bare Boltzmann factor, ignoring any formation entropy prefactor). Calculate n/Nn/N at T=900 KT = 900\,\mathrm{K}.

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