Scale-Bridging Simulation of Functional Composites (SFC)
Ferroelectric perovskites (ABO3, with A: alkali earth metals and B: transition metals) are widely used in applications and are promising for energy harvesting devices as well as for future efficient solid-state cooling devices based on the electrocaloric effect (see: presentation „New concepts for cooling: Origins of the invers electrocaloric effect at Universidad Nacional Autónoma de México“) . All these applications share the following demands on materials design: Replace toxic Pb and increase efficiency and reversibility in a broad and suitable operation range (cooling: At and below room temperature, others: At and above room temperature).
The goal of the group is the design of ferroelectric composites with superior functional properties. We will simultaneously optimize multiple responses with high technological impact for (a) harvesting of electric energy from temperature fluctuations or stress and (b) cooling by means of the electrocaloric effect. Our approach is the scale-bridging optimization of composite systems with different morphologies: (a) superlattices (b) pillars and (c) inclusions, combining the benefits of materials choice, controlled inhomogeneities, domain structure, and the boundary conditions at the interfaces. Our methods are scale-bridging simulations based on ab initio parametrization with high predictive power, which allow us to fundamentally understand and design the properties of materials systems.
Scale-bridging simulation of domain walls and inhomogeneities in (Ba,Sr)TiO3: (a)—(b) Local polarization and field-induced polarization switching at moving 180° domain walls. (a) The wall propagates through the system and switches polarization in successive layers by nucleation and growth on the wall as shown in (c).
(d) For a homogenous distribution of substituents the main impact of Sr is a reduction of transition temperatures. (e) Different local atomic ordering however modify subtle details and nano-scale inhomogeneities (d) turn the material properties inside out.
- Molecular dynamics;
- Density functional theory;
- Domain walls and phase transitions
- Magneto- and electrocaloric effects;
- Ferroic materials;
- Functional (piezoelectric, dielectric, caloric) responses
Prof. Dr. Anna Grünebohm
Tel: +49 234 32 26433
Fax: +49 234 32 14977
- Complex Phase Transitions in Solids (lecture with hands-on and project; summer semesters; in collaboration with the Faculty of Physics and Astronomy, open for UNIC, master)
- Advanced Atomistic Simulations (lecture with hands-on; winter semesters; in collaboration with M. Mrovec,, open for UNIC, master)
- Scale-bridging Simulations of Functional Composites (seminar, every semester)
- Material- Festkörperphysik II (lecture, summer semesters, bachelor)
- Quantum Mechanics (lecture with exercises, master)
- Documenting and Communicating Science (lecture with hands-on, winter semester)
PhD-position (m,f,x) for 3 years
Student Projects and Theses
A list of research projects and theses currently offered in the research group Scalebridging Simulation of Functional Composites can be found here
Furher the group offers two projects in the RUB-China Scholarship Council (CSC) Program
- Ferroelectric phase diagrams and functional properties of hybrid ferroelectrics
- Functional properties of ferroelectric superlattices: an ab initio based scale-bridging study on BaTiO3/Ba(Ti,Sn)O3
A list of past master theses can be found here