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RESEARCH PRODUCT

Semi-empirical supercell calculations for free- and bound-hole polarons in crystal

subject

description

Two different parametrizations of the semi-empirical method of the intermediate neglect of the differential overlap (INDO) are applied to the calculations of the small-radius hole polarons in the corundum crystal. The 80-atom supercell has been used for the study of the atomic and electronic structure of a free small-radius hole polaron (the self-trapped hole, STH) and a hole polaron bound by a Mg impurity (the so-called centre), respectively. Both parametrizations indicate that the two-site (quasi-molecular) configurations of both kinds of polaron have the lowest energy (which does not exclude the existence of one-site polarons also characterized by considerable relaxation energies). For centres the lower energy is calculated for the defect configuration where the Mg-ion substitution is nearest to the hole polaron. Experimental ENDOR data on defects are discussed in the light of the calculations.