Variation of peak F-band absorption energy and lattice distortion with pressure has been calculated for lithium halides employing extended ion model and using values of local compressibility in the neighbourhood of the F-centres which include the effect of vacancy and pressure. The calculated results are in very good agreement with experimental results.

Pressure variation of maximumF-band absorption energies in the halides of lithium, sodium and potassium has been investigated employing the extended-ion approximation for the calculation of theF-electron energy eigenvalues and using values of local compressibility in the neighbourhood of theF-centres which include the effect of vacancy and pressure. The results obtained agree with the experimental results.