Special Seminar in Condensed Matter Physics: "Ab-initio electronic structure calculations of Transparent Conducting Oxide (TCO) materials "
Starts 8 Feb 2012 16:30
Ends 8 Feb 2012 20:00
Central European Time
Leonardo da Vinci Building Luigi Stasi Seminar Room
Strada Costiera, 11
I - 34151 Trieste (Italy)
Transparent Conducting Oxides (TCO) constitute an unique class of materials which combine two physical properties - transparency for visible spectrum and high electrical conductivity together. TCO's are widely used in a variety of technological applications and are subject of active experimental and theoretical research. Development of an electronic structure method capable of accurately describing the key physical properties of TCO namely - the band gap and electron effective mass has been a subject of enduring interest.
In this talk, I will first discuss the electronic band structure of basic TCO's calculated using density functional theory (DFT). It is observed that although the structural parameters are correct, the DFT band gap are severely underestimated compared to experiment. Since DFT is a ground state theory and in principle the Kohn-Sham gaps can not be compared with the experiment, we use the state of the art - GW approximation technique to calculate the excited states. The implementation of the GW approximation within ABINIT code will be presented in brief. The modifications in the pseudopotential necessary for accurate calculation of the self-energy within the GW approximation is discussed with the help of a systematic study of the pseudopotentials for ZnO. The GW results are presented for ZnO, SnO_2 and ZnX_2O_4 (X=Al, Ga and In) spinel structure. Finally I will also discuss the electronic band structure calculated using the computationally inexpensive Tran-Blaha modified Becke-Johnson potential (TB-mBJ) scheme for prototype TCO's and formation energies of native point defects in ZnAl_2O_4 spinel structure.