The formation volume of Frenkel defect in silver halides

The formation volume ν_f of a (cation) Frenkel Defect is calculated in AgCl and AgBr. The proposed formula for ν_f has no adjustable parameters and contains the formation enthalpy (of a Frenkel defect), the compressibility of the solid at absolute zero and the pressure derivative of the compressibility. The calculated values are in good agreement with the experimental results.