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We have investigated the formation energies and electronic structure of native defects in ZnO by a first-principles plane-wave pseudopotential method. When p-type conditions are assumed, the formation energies of donor-type defects can be quite low. The effect of self-compensation by the donor-type defects should be significant in p-type doping. Under n-type conditions, the oxygen vacancy exhibits the lowest formation energy among the donor-type defects. The electronic structure, however, implies that only the zinc interstitial or the zinc antisite can explain the n-type conductivity of undoped ZnO.

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Migration energies of Li ion in Li 3 N, Li 2 X (X=O, S, Se, and Te) and LiX (X=F, Cl, Br, I) via vacancy mechanism have been calculated by first principles pseudopotential method using plane-wave basis. The energy was obtained as the difference in total energies of supercells by two separate calculations; one with a Li + ion at the normal point and the other with a Li + ion at the saddle point. Positions of atoms within the second nearest neighbor of the jumping ion were fully relaxed. Two kinds of diffusion paths, i.e., direct and indirect jumps, were considered. Results show rough agreement with available experimental data. The migration energies for the indirect jump in both halides and chalcogenides show a tendency to decrease with the increase in the periodic number in the Periodic table. This is consistent with the widely accepted view. However, the migration energies for the direct jump of chalcogenides do not obey the rule. Comparison of two polymorphs of LiF implies that not only the anionic species but also the crystal structure plays an important role in determining migration energy.