Designing materials for optoelectronics and energy applications

A prerequisite towards the design of novel materials in the fields of energy efficient optoelectronics, power electronics, catalysis, or superconductivity, is to understand, describe and predict the complex interplay between their structural, thermodynamic, magnetic, optoelectronic and electronic properties. Apart from bulk, interfaces (solid-solid, solid-liquid, and solid-gas) and surfaces, both at the nano- and the micro-meter scales, are of paramount importance in the design and the properties of these materials. Density functional theory calculations constitute the working horse in addressing and exploring the aforementioned interplay.

Screw dislocation induced nanopipes are investigated by combining elasticity theory with density functional theory calculations. Based on these calculations a c-type screw dislocation phase diagram is constructed which describes the energetically most favorable core structures as function of the Ga, N and H chemical potentials. We find that nanopipes with diameters ranging from ≈1 to ≈2 nm are energetically favorable for high values of the H chemical potential and conditions that correspond to MOCVD and MOVPE growth. [more]
The synthesis of InGaN digital alloys in the form of short period InGaN/GaN superlttices is investigated by combining ab/initio and empirical potential calculations with PAMBE growth , Photoluminescence Spectroscopy, and HR(S)TEM characterization. [more]
The aim of this project is to resolve the interplay of real space structure and electronic states in combination with magnetic disorder for iron-based superconductors.  We apply a combination of density-functional theory calculations and effective tight-binding models for the electronic energy dispersion. [more]
The thermodynamic stability of computationally designed multicomponent compounds against decomposition into structures with less favorable properties is often unclear. In this project, we have used sophisticated finite temperature ab initio methods to determine the relative phase stabilities of promising Ce-Fe-Ti hard-magnetic materials. [more]
The fundamental mechanisms of V-pits formation on epitaxially grown GaN polar surfaces are investigated combining state-of-the-art first-principles calculations and elasticity theory.
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