F‐Centre in KCl with the Extended Polarizable Ion Lattice Model

The F‐centre in KCl has been calculated within the same approximations as those used in calculations of the bottom of the conduction band in KCl. It is found that if the electronic polarization of the crystal is neglected, the calculated values of the optical excitation and optical ionization energies are 1.5 and 2.5 times the corresponding experimental values. The difference between the calculated and the experimental values is reduced considerably when the polarization potential is incorporated to account for the electronic polarization.