Advancing Multiscale Simulation Methods

Most phenomena relevant for material science are best targeted by specific theoretical frameworks and simulation methods. For realistic description of material behavior, the department develops new schemes to couple elementary approaches and study their interplay in a systematic way.

Uncertainty Propagation for Density Functional Theory

method development

While Density Functional Theory (DFT) is in principle exact, the exchange functional remains unknown, which limits the accuracy of DFT simulation. Still, in addition to the accuracy of the exchange functional, the quality of material properties calculated with DFT is also restricted by the choice of finite bases sets.
[more]

Mean Field Potentials for Anharmonic Behaviour

The evaluation of anharmonic free energies of material phases is vital for the generation of thermodynamic phase diagrams. This project explores the concept of obtaining these free energies analytically from a bond lattice mean field model. The advantage of such an approach is that the computational cost is negligible compared to the traditional approach of thermodynamic integration.
[more]

Electronic Passivation Schemes

Using technologically interesting examples, such as wurtzite surfaces, we develop a robust passivation scheme for density-functional-theory surface calculations of materials exhibiting spontaneous polarization. The novel approach enables computationally efficient and accurate surface electronic structure calculations. [more]

Orbital Contrast in Field Ion Microscopy

method development

We simulate the ionization contrast in field ion microscopy arising from the electronic structure of the imaged surface. For this DFT calculations of the electrified surface are combined with the Tersoff-Hamann approximation to electron tunneling. The approach allows to explain the chemical contrast observed for NiRe alloys.

Microscopic Origins of Fracture Toughness

microstructure and properties

This ERC-funded project aims at developing an experimentally validated multiscale modelling framework for the prediction of fracture toughness of metals.

Non-radiative recombination in optoelectronic devices

Optoelectronic devices allow for the direct conversion of light and electrical energy. The performance of such optoelectronic devices is limited by losses due to non-radiative recombination. We have looked at the solar cell material Cu(In,Ga)Se₂. We identified not only an effective recombination pathway at high Ga contents involving configuration changes of Ga or In anti-sites, but also extended the charge corrections to the computation of configuration coordinate diagrams.

Field-Controlled Evaporation Mechanisms for Surface Atoms

Extremely strong (~10 V/nm) electric fields rupturing atomic bonds is a relatively well-studied concept in the field of molecular chemistry. When extended to crystalline systems, i.e. material surfaces, this concept is known as field evaporation and its exact mechanisms become more challenging to predict. Field evaporation is the central phenomenon that enables atom probe tomography (APT) and 3D field ion microscopy (3D-FIM), and obtaining atomically-accurate APT reconstructions will be impossible without an atomically-accurate understanding of how ions initially form and depart from the surface. By performing first-principles calculations on faceted surfaces under extreme fields, we search for such an understanding in pure metals and alloys.