research topics

Ab initio simulations are employed to investigate materials at the basis of modern energy technology, such as thermoelectric converters and solar cells, and non-volatile memory for computers

theory of thermoelectric properties of self-assembled nanocrystals in semiconductor matrix, segregation and ordering in ternary metal or semiconductor alloys, atomic-scale modeling of semiconductor nanowire growth theory of non-adiabatic electronic excitations at surfaces theory of vibrational damping in adsorbates and thin surface layers multi-scale modeling of materials with optimized transport properties

Following demands for materials with peculiar transport properties, e.g. in photovoltaic, spintronic or thermoelectric applications, there is a need for materials modeling at the quantum-mechanical level. We aim at developing both the conceptual basis and the software tools for interfacing density-functional calculations with scale-bridging simulation tools to establish the interrelation between the macroscopic transport properties and the atomic structure of materials. For examples, magnetic alloys for spintronics display a high level of spin polarization only if highly ordered. Ab initio thermodynamics needs to be combined with a cluster expansion of interactions in disordered systems to screen the huge configuration space for materials with novel properties. Nanostructured semiconductors, e.g. with a regular arrangement of nano-scale inclusions ("quantum dot crystals"), hold the promise of high thermoelectric figure of merit. Simulating their geometry-controlled properties requires the development of multi-scale simulation tools where the lowest scale involves a quantum treatment of systems with up to a million atoms.

Examples
 

Heusler Alloy (ferromagnetic half metal)

manganese silicide layer on silicon

electronic wavefunction of a Si27 cluster
 

InAs quantum dot on gallium arsenide