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Maximally localized Wannier functions in antiferromagnetic MnO within the FLAPW formalism
No full textSelf-energy corrections in VO2 within a model GW scheme
No full textWe discuss the electronic properties of VO2 in its monoclinic, insulating phase, by comparing the results of quasiparticle band structure calculations obtained within a model GW scheme with those of both LDA calculations and available experiments. Our calculations are based on the full-potential-linearized-augmented-plane-wave method. We obtain the correct energy gap for this compound and a density of states consistent with photoemission results. Moreover, we show that model GW calculations reproduce satisfactorily the imaginary part of the dielectric constant as obtained by optical and EELS measurement
Born charge differences of TiO2 polytypes: Multipole expansion of Wannier charge densities
No full text
Ab-Initio study of piezoelectricity and spontaneous polarization in ZNO
No full textWe demonstrate the feasibility of ab initio studies of piezoelectricity within an all-electron scheme. The focus of our analysis is on wurtzite ZnO; for comparison, some results are also presented for the related materials BeO and ZnS. The comparative study is performed in order to understand the microscopic origin of the peculiar behavior of ZnO, whose piezoelectric response is the strongest among the tetrahedrally bonded semiconductors. In all such materials, the piezoelectric effect results from two different terms of opposite sign: these are usually referred to as the ''clamped-ion'' and the ''internal-strain'' contributions. Cancellation amongst them is least effective in ZnO, where the dominant effect is due to a rigid-ion-like mechanism. Furthermore, we compute the spontaneous polarization of ZnO and we discuss the puzzling agreement between our calculated value and a very indirect experimental estimate of the same quantity
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