Profile of Michael Engel

Research Interests

Recent research images

Liquid-Hexatic coexistence in the hard disk system
Self-assembly of nanoplates in theory and experiment

Left: Large-scale simulation of the melting transition in a system of hard disks. The configuration of the six nearest neighbors specifies a local orientation, which is color coded. A discontinuous (first order) phase transition from the liquid to the hexatic phase is observed. The image shows phase coexistence.
Reference: Physical Review E 87, 042134 (2013)

Right: A joint computational-experimental study on the self-assembly of rare earth nanoplates. The particles are characterized by patchy interaction at their edges. Ab-initio calculations confirm a non-uniform covering with screening polymers, which explains the formation of an alternating phase in Monte Carlo simulations.
Reference: Nature Chemistry 5, 466 (2013)


Self-assembly of soft matter

Interactive java visualization

My research focuses on understanding the self-assembly of soft matter into ordered phases by varying the shape and interaction of nanoscopic building blocks. The goal is control over the assembly process and the search for novel materials with target structures and properties.

Examples of soft matter are nanocrystals, colloids, polymers, foams, granular materials, and some biological systems. Typical particle sizes and length scales range from a few nanometers up to ten micrometers. There are many similarities with "hard" matter such as solids, glasses, metals, insulators, and semiconductors, which can be exploited for soft matter research.

The image shows families of 145 symmetric polyhedra, which have been self-assembled and packed into complex ordered structures to study the role of shape in nanoparticles, colloids, and viruses.


Particle simulation and visualisation

Interactive java visualization

Many-particle simulations using CPUs or multi-core graphics processors (GPUs) provide full control and full knowledge over all parts of the system under investigation and allow a direct determination of the phase behavior via free energy calculations.

I am developing novel simulation methods for Monte Carlo and Molecular Dynamics and efficient visualization tools inspired by experiment for structural analysis. I am also interested in interactive simulations, because they speed up research and provide a direct intuition for the underlying physical processes.

The image shows an interactive Monte Carlo simulation of cubes with various observables using own simulation and visualization tools.


Structural complexity and quasicrystals

Crystal growth with anisotropic particles

Quasicrystals have long-range order without periodicity. They were originally discovered in alloys, but have recently also been reported in soft matter systems of micelles, macromolecules and binary colloids. Aperiodic order is also found in modulated phases, which are known in inorganic compounds, metals under pressure and organic materials. The role of geometric frustration and competing length scales is not well understood.

In my work, I am studying the connection between spatial order and physical properties using computer simulations. The aim is to develop an understanding for the connection between building block and assembled structure by investigating the origin of structural complexity.

The image shows a dodecagonal quasicrystal formed in a computer simulation from a fluid of hard tetrahedra. The image was featured as BBC Science image.