306-312<span style="font-size:14.0pt;line-height:
115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">The Schottky defect formation process in MgO, CaO, SrO, and BaO is investigated using our
recently introduced EPPI model3. We find that inclusion of
quadrupolar interactions makes a substantial contribution to the formation
energy by values ranging from 1.2 eV to 2.9 eV. The EPPI values of the
enthalpies (hfs) are 5.9, 5.8, 4.7 and 1.4
eV respectively for MgO, CaO, SrO, and BaO. The results of cation self
diffusion experiments in MgO are reanalyzed to include the effects of
impurity-vacancy association reaction. The analysis suggests the previous
interpretation of the experimental data to be an oversimplification. Since the
binding energy of an impurity - defect complex in MgO could be quite large, the
effects of the association reaction on the defect densities are appreciable. On
the basis of near complete association of the dominant tetravalent cation impurity,
hfs in MgO is found to be 5.8 eV which is in good
agreement with the theoretical value of the present work.</span