COND MATT Seminar on 8 February 2012

[ivanisse]

SPECIAL SEMINAR IN CONDENSED MATTER PHYSICS

Tuesday, 8 February 2012  -   16:30 a.m.

Luigi Stasi Seminar Room - Leonardo Bldg. - 1st floor


Hemant Dixit (University of Antwerp, Belgium)

" Ab-initio electronic structure calculations of Transparent Conducting 
Oxide (TCO) materials  "

Abstract:

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.