INTERMEDIATE-COUPLING POLARON IN A TERNARY MIXED-CRYSTAL

The intermediate-coupling polaron in a ternary mixed crystal AxB1-xC is studied within the framework of the random-element-isodisplacement (REI) model. The self-trapping energy and effective mass of the polaron are analytically derived in the mono-phonon approximation. The numerical results of the electron-LO phonon coupling constants, self-trapping energies and effective masses of the polarons for several mixed crystal materials are obtained as functions of the composition x. It is found that there is a minimum of the polaron effects at a intermediatary value of the compositions for either the one-mode or two-mode behaviour mixed crystals. The reduction of electron-LO-phonon interaction observed recently in the AgClxBr1-x (0 less-than-or-equal-to x less-than-or-equal-to 0.21) mixed crystals can be qualitatively explained by our theoretical results.