Following the annual tradition, we made another summer excursion, this year to Brombachsee. There we explored Abenteuerwald Enderndorf (including the zipline) and enjoyed a relaxing afternoon at the beach. Thanks all for joining!
How do a small number of larger colloidal particles behave when mixed with many smaller ones inside spherical droplets? We found that entropy alone drives the larger particles to the droplet surface, where they consistently settle at the twelve vertices of an icosahedral structure formed by the smaller particles. Using a combination of experiment and simulation, we showed that this trapping effect is robust and results from the system’s tendency to maximize free volume during self-assembly. These findings offer new insight into how complex structures can form without external guidance and support the design of programmable materials through simple physical principles.
Read about this work here:
Praveen K. Bommineni, Junwei Wang, Nicolas Vogel, Michael Engel
Entropic Trapping of Hard Spheres in Spherical Confinement
Physical Review Letters 134, 198201 (2025)
Scientists have long known that the shape of tiny crystals (nanocrystals) can affect their properties, such as how they interact with light or how well they function as catalysts. However, precisely understanding how these shapes form has been challenging, since many factors are involved: temperature, chemicals in the solution, and even the arrangement of atoms at the crystal’s edges. In this study, the researchers introduced a theoretical and computational approach that focuses on the critical spots where atoms attach as the crystal grows. By examining the energy required to add atoms at these sites, they explain why certain shapes, including cubes, octahedra, or other symmetrical forms, often appear.
Beyond explaining why various shapes emerge, this method can guide experimental design. It enables scientists to predict which conditions favor different morphologies and to control crystal growth toward specific outcomes. The study shows that the first atom to grow on the surface, referred to as the adatom, dominates the process by creating temporary pathways that lead to particular shapes. This new understanding not only clarifies how nanocrystals form but also suggests ways to refine their shapes for targeted uses in technology and medicine.
Read about this work here:
Carlos L. Bassani, Michael Engel
Kinetically Trapped Nanocrystals with Symmetry-Preserving Shapes
Journal of the American Chemical Society 147, 9487-9495 (2025)
The Engellab continued a scientific exchange with the group or Sudeep Punnathanam at the Indian Institute of Science (IISc). As part of this Indo-German exchange, multiple mutual visits were organized in 2023 and 2024.
IISc is a leading research university located in Bengaluru (Karnataka). The research of our Indian partner concerns Enhanced Computational Research in Phase Transitions (EnCRIPT). The exchange was funded by the German Academic Exchange Service (DAAD — Deutscher Akademischer Austauschdienst) over two years.
Michael Engel attends the 2024 AIChE Annual Meeting in San Diego to present present his research and promote our department of Chemical and Biological Engineering of FAU. The department has an evening reception and participates in the recruitment fair.
Surface strain can help increase the performance of nanocatalysts, and we have designed a new strategy to stabilize the surface strain in materials. The groups of Yimo Han and Matthew R. Jones at Rice University synthesized nanoparticles and used four-dimensional scanning transmission electron microscopy (4D-STEM) to capture an electron diffraction pattern at each scan position, which produces detailed structural information. Molecular dynamics simulations of Alberto Leonardi investigated the inhibition of dislocation nucleation due to reduced shear stress at corners.
Read about the research here:
Chuqiao Shi, Zhihua Cheng, Alberto Leonardi, Yao Yang, Michael Engel, Matthew R. Jones, Yimo Han
Preserving Surface Strain in Nanocatalysts via Morphology Control
Science Advances 10, eadp378 (2024)
Michael Engel visited the Computational Statistical Physics lab of Masaharu Isobe at Nagoya Institute of Technology University from July 4 to July 17. NITech is a partner university of FAU in Japan. Discussions advanced our understanding of the hard disc problems, in particular using event-chain methods and Voronoi decomposition.
This year we went canoeing on the river Pegnitz near Vorra. Great fun, including some excitement, and a relaxing dinner and evening walk afterwards. See you again next year!
Nydia Varela-Rosales defended her thesis and obtained a PhD in Physics. The title of her thesis is: “Computational Design and Thermodynamic Stability of Aperiodic Crystals and their Approximants”.
Congratulations!
For the time June to November 2024 Praveen Bommineni from the National Institute of Technology Warangal (India) is conducting research in our group. A focus of joint research is colloidal crystallization in confinement. The research is funded through the guest research program of FAU and the CRC 1411. Praveen has been a postdoctoral research in the group and returning for a sabbatical.
Welcome to Erlangen!