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Sonderforschungsbereich 595

Quantum mechanical computer simulations on the electronic- and defect structure of oxides

Prof. Dr. K. Albe (Div. Material Modelling)
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The aim of the project is to identify lead-free ferroelectric materials with improved properties which can be used as a non-toxic alternative for the technologically established PZT. Different materials (Bi(Me)-BaTiO3, Me = Zn, Mg, Ti, Nb) will be investigated with the aid of calculations based on Density-functional theory. Emphasis is placed on the determination of the morphotropic composition, spontaneous polarisation P as well as piezoelectric and dielectric properties. Initially, the calculations will be performed within the virtual crystal approximation (VCA), where pseudopotentials are used as virtual mixed atoms. As an alternative, computationally expensive direct calculations can be made using large supercells. Beside the studies on lead-free systems, investigations on (doped) PZT will be conducted in order to elucidate the thermodynamics and kinetics of vacancies. In doing so, firstly the boundary phases PT and PZ will be considered.

In the area of battery materials, quantum mechanical studies on the electronic and spin structure of Li1-x(Co,Ni)O2 will be carried out along with spectroscopic investigations (ResPES and EPR). Furthermore, structure optimizations are planned to study the predominant defect structures in Li1-x(Co,Ni,Mn)O2 which are produced by fatigue.