F-Centre Theory in Multivalley Cubic Crystals

The interaction between an electron bound to a Coulomb potential and the LO lattice vibrations in a cubic multivalley ionic crystal is considered for not too weak coupling. The vibrational degrees of freedom in the partition function of the system are eliminated by Feynman's ordered‐operator technique. The complicated operator thus obtained depends only on the electron variables and is approximated by a suitable operator containing some available parameters. The latter provides to calculate the partition function of the F‐centre by means of a variational principle at arbitrary temperatures and thus to obtain the ground state energy of the F‐centre as a function of coupling parameters and of the anisotropy of electron band masses. [Russian Text Ignored]