Exp-Ana-Sim collaboration on magic clusters

In a joint collaboration combining experiment (synthesis and self-assembly), analysis (electron microscopy including tomography), and simulation (molecular dynamics and free energy calculations), a team from FAU involving Junwei Wang and Chrameh Mbah reported magic number colloidal clusters:

“Clusters in systems as diverse as metal atoms, virus proteins, noble gases, and nucleons have properties that depend sensitively on the number of constituent particles. Certain numbers are termed ‘magic’ because they grant the system with closed shells and exceptional stability. To this point, magic number clusters have been exclusively found with attractive interactions as present between atoms. Here we show that magic number clusters exist in a confined soft matter system with negligible interactions. Colloidal particles in an emulsion droplet spontaneously organize into a series of clusters with precisely defined shell structures. Crucially, free energy calculations demonstrate that colloidal clusters with magic numbers possess higher thermodynamic stability than those off magic numbers. A complex kinetic pathway is responsible for the efficiency of this system in finding its minimum free energy configuration. Targeting similar magic number states is a strategy towards unique configurations in finite self-organizing systems across the scales.”

Read about it here:

Magic Number Colloidal Clusters as Minimum Free Energy Structures
J. Wang, C.F. Mbah, T. Przybilla, B.A. Zubiri, E. Spiecker, M. Engel, N. Vogel
Nature Communications 9, 5259 (2018)

Milestone paper

A paper involving Michael Engel with coauthors Joshua Anderson and Sharon Glotzer from University of Michigan, Masaharu Isobe from Nagoya Institute of Technology, Etienne Bernard then from Massachusetts Institute of Technology, and Werner Krauth from École Normale Supérieure has been chosen as a Milestone Paper “that made significant contributions to their field” among all articles published in the journal Physical Review E in 2013.

Hard-disk equation of state: First-order liquid-hexatic transition in two dimensions with three simulation methods
Michael Engel, Joshua A. Anderson, Sharon C. Glotzer, Masaharu Isobe, Etienne P. Bernard, and Werner Krauth
Phys. Rev. E 87, 042134 (2013)

Summer of conferences

Several members of the lab traveled to present and promote their newest research results at conferences throughout Germany:

Controlling nanocrystal shapes

In a recent ACS Nano publication, Alberto Leonardi proposes an etching synthesis method for controlling the shape of core-shell nanocrystals:

“The application of nanocrystals as heterogeneous catalysts and plasmonic nanoparticles requires fine control of their shape and chemical composition. A promising idea to achieve synergistic effects is to combine two distinct chemical and/or physical functionalities in bimetallic core@shell nanocrystals. Although techniques for the synthesis of single-component nanocrystals with spherical or anisotropic shape are well-established, new methods are sought to tailor multicomponent nanocrystals. Here, we probe etching in a controlled redox environment as a synthesis technique for multicomponent nanocrystals. Our Monte Carlo computer simulations demonstrate the appearance of characteristic non-equilibrium intermediate microstructures that are further thermodynamically tested and analyzed with molecular dynamics. Convex platelet, concave polyhedron, pod, cage, and strutted-cage shapes are obtained at room temperature with fully coherent structure exposing crystallographic facets and chemical elements along distinct particle crystallographic directions. We observe that structural and dynamic properties are markedly modified compared to the untreated compact nanocrystal.”

Read about it here:

Particle Shape Control via Etching of Core-Shell Nanocrystals
A. Leonardi, M. Engel
ACS Nano 12, 9186-9195 (2018)

Artistic visualization of core-shell nanocrystal etching. Image credit: Alberto Leonardi.

MSS excursion 2018

The MSS Institute organized a trip to Fränkische Schweiz that consisted of a canoe/kayak ride down the river Wiesent from Wiesental and a short hike up the hill where we had a beautiful view and lunch under a big Tilia tree.

We all arrived back at the rental station without getting too (but still a little bit) wet.

View from Gasthaus zum Pfaffenstein in Moritz.

Quasicrystals in Scotland

Michael Engel presented the opening lecture at the ICMS conference “Quasicrystals: pattern formation and aperiodic order” in Edinburgh. This conference brought together four different research communities to advance the understanding of quasicrystals and aperiodic order: (i) quasicrystals in materials science, (ii) quasicrystals in soft matter, (iii) quasicrystals in partial differential equations and (iv) quasicrystals in aperiodic tilings.

Apply now: Ferienakademie 2018

Nils Thuerey, Miriam Mehl and Michael Engel are offering again this fall a student course at Ferienakademie in the Italian Alps. The topic is Accelerating Physics Simulations with Deep Learning. The course is open to students at FAU Erlangen, TU Munich and U Stuttgart and will be a combination of presentations given by the participants and project-based team work. Read more our plans here.

Prerequisites for this course are basic programming skills, a sympathy for numerics and stochastics and the ability to work in a team on a project involving not only theory but also real hands-on coding (C/C++, Python, and similar). Hurry up! Applications are open a few more days until May 2, 2018.

Importantly, there is not only time for science but also time for wonderful hiking around Sarntal, Tyrol. Below is a picture from last year’s course:

Welcome Praveen

Praveen Bommineni joined the group as a postdoctoral researcher. He will be working on simulations to resolve structure formation processes in mesoscale systems. Welcome!


Marco Klement represented the group at the annual meeting of the German Physical Society (DPG) held this year in Berlin. He presented about “Efficient Simulation of Anisotropic Particles”. The 2018 meeting was the largest physics meeting ever to be organized in Europe, with 6420 attending.

Dancing robots

A publication with experiments by Christian Scholz, then a postdoc at MSS and now at Universität Düsseldorf, appeared in Nature Communications:

“Biological organisms and artificial active particles self-organize into swarms and patterns. Open questions concern the design of emergent phenomena by choosing appropriate forms of activity and particle interactions. A particularly simple and versatile system are 3D-printed robots on a vibrating table that can perform self-propelled and self-spinning motion. Here we study a mixture of minimalistic clockwise and counter-clockwise rotating robots, called rotors. Our experiments show that rotors move collectively and exhibit super-diffusive interfacial motion and phase separate via spinodal decomposition. On long time scales, confinement favors symmetric demixing patterns. By mapping rotor motion on a Langevin equation with a constant driving torque and by comparison with computer simulations, we demonstrate that our macroscopic system is a form of active soft matter.”

Read about it here:

Rotating Robots Move Collectively and Self-Organize
C. Scholz, M. Engel, T. Pöschel
Nature Communications 9, 931 (2018)

Press coverage pro-physik.de (in German):
Roboter mit Fraktionszwang