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Parameter-free calculations of electronic properties and optical transitions of MgO, ZnO, and CdO

Friedhelm Bechstedt ,  André Schleife ,  Frank Fuchs ,  Claudia Rödl 

Friedrich-Schiller-Universitaet (IFTO), Max-Wien-Platz 1, Jena 07743, Germany

Since Moore's law still holds, not only do computational capabilities evolute rapidly but at the same time the cost per GHz drops dramatically. This development allows the implementation of computationally expensive high-quality ab-initio methods that were out of reach only a few years ago. Undoubtedly, ab-initio methods are an inevitable tool for materials science and even high-end materials design.

We briefly introduce the theoretical concepts of one of the currently most reliable ab-initio approaches to the computation of electronic band structures. We use the nonlocal hybrid HSE03 functional as an approximation to exchange and correlation in a generalized Kohn-Sham equation to compute the starting point for the solution of the quasiparticle equation. Using this starting electronic structure we compute quasiparticle energies within the GW approximation which involves screening from the fully frequency-dependent dielectric function. Spin-orbit coupling is included in our calculations.

We present highly accurate electronic band structures of MgO, ZnO, and CdO, which we use to derive fundamental gaps, effective electron and hole masses, crystal-field and spin-orbit splittings, optical transition matrix elements, and even exciton binding energies. Chemical trends are pointed out. Since we are not limited to the equilibrium lattice structures of these materials, we predict and compare to values for the wurtzite polymorphs of MgO and CdO. Both become important in alloys and heterostructures of MgO and CdO together with wz-ZnO, e.g., for band-gap tailoring. However, it is practically impossible to fabricate samples of sufficient quality for experimental studies.


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Related papers

Presentation: Poster at E-MRS Fall Meeting 2009, Symposium C, by Friedhelm Bechstedt
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-07 11:57
Revised:   2009-06-17 15:27