The electronic state of O^2- in MgO studied by the Compton profile method

The electronic state of the O^2- ion in MgO is studied in detail by measuring the isotropic Compton profile and profiles in crystal directions [100], [110], and [111]. The theoretical profiles are calculated using linear combinations of local orbitals orthogonalized to each other symmetrically. The orthogonalization is performed with the 'exact' cluster method. Nine different local wave functions of the O^2- ion have been used as the basis of the calculations. The experimental and theoretical profiles as well as their Fourier transforms are compared with each other. The orthogonalized Watson +1 potential-well wave function and the orthogonalized LCAO band function of Pantelides, Mickish & Kunz [Phys. Rev. B. (1974), 10, 5203- 5212] were found to describe best the ionic state of O^2- even though neither of the functions gives complete agreement with the experiment.