Using a hybrid Hartree–Fock
(HF)-DFT method combined with
LCAO basis set and periodic supercell approach, the atomic, electronic
structure and phonon properties of oxygen vacancies in ZnO and SrTiO3 were calculated and compared. The important role of a ghost
basis function centered at the vacant site and defect spin state for
SrTiO3 is discussed. It is shown that the use of hybrid
functionals is vital for correct reproduction of defects basic properties.
The Gibbs free energy of formation of oxygen vacancies and their considerable
temperature dependence has been compared for the two oxides. These
calculations were based on the polarizability model for the soft mode
temperature behavior in SrTiO3. The supercell size effects
in the Gibbs free energy of formation of oxygen vacancies in the two
oxides are discussed. The major factors for the quite different behavior
of the two oxides and the degree of electron delocalization nearby
the oxygen vacancy have been identified.
We present a comprehensive first-principles study of the electronic charge redistribution in atomically sharp LaAlO3/SrTiO3(001) heterointerfaces of both n-and p-types allowing for nonstoichiometric composition. Using two different computational methods within the framework of the density functional theory (linear combination of atomic orbitals and plane waves) we demonstrate that conducting properties of LaAlO3/SrTiO3(001) heterointerfaces strongly depend on termination of LaAlO3(001) surface. We argue that both the "polar catastrophe" and the polar distortion scenarios may be realized depending on the interface stoichiometry. Our calculations predict that heterointerfaces with a non-stoichiometric film-either LaO-terminated n-type or AlO2-terminated p-type-may exhibit the conductivity of n-or p-type, respectively, independently of LaAlO3(001) film thickness.
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