Carlos Lange Bassani received an EAM Starting Grant. This grant is an encouragement for young researchers to venture into inovative and risky projects, and is a stepping stone towards ERC grant applications. Congratulations!

Simulation vs. microscopy images of nanocrystal habits. Simulations use rejection-free kinetic Monte Carlo to grow realistic-sized nanocrystals atom-by-atom. References of microscope images: [1] Xia et al., J. Am. Chem. Soc. 2012, 134, 1793; [2] Ahn et al., J. Mat. Chem. C 2013, 1, 6861; [3] Chen et al., Nature Comm. 2020, 11, 3041; [4] Sun et al., ACS Nano 2021, 15, 15953, [5] Xia and Xia, Nano Lett. 2012, 12, 6038; [6] Langille et al., Science 2012, 337, 954.

Nanocrystal (NC) superlattices are a novel way to design functional materials. Nanomaterial chemists thrived in forming NCs with controlled size and shape and assembling them into superstructures. Functionality of these materials relies on precise control of NC habits and superstructure formation, as well as on the electronic coupling between NCs –that is, it is an inherently multiscale process–, but multiscale models did not keep pace with recent advances in the field.

The proposed project upscales from atomic to realistic-sized NCs with 10s-of-millions of atoms via rejection-free kinetic Monte Carlo based on the semi-Gibbs ensemble. Of interest is the role of strain accumulation affected by defects, lattice mismatch, and geometric frustration, thus kinetically entrapping NCs into lower symmetry habits –that is, NC shapes that do not comply with the symmetry of the underlying crystalline structure. Coupling with reactor scales (the environment) to understand mass transfer-limited crystallization is also pivotal to predicting the yield of denser NC populations. A multiscale understanding from atom-to-NC-to-environment will optimize NC synthesis conditions and design strategies for new NC habits.

The tetrahedral geometry is ubiquitous in natural and synthetic systems. Regular tetrahedra do not tile space, which makes understanding their self-assembly behavior a formidable challenge. In 2009, simulations of hard tetrahedra —that is particles with the shape of a regular tetrahedron, interacting only by excluded volume interactions— discovered a dodecagonal quasicrystal stabilized by entropy alone. But while this quasicrystal forms robustly and reproducibly in simulation, it competes with periodic approximants and cannot be the thermodynamic ground state in the limit of infinite pressure. In this limit, the densest packing will eventually prevail, which is a simple (in comparison) dimer crystal.

Finally, after 14 years, our simulation predictions are confirmed. Yi Wang from the group of Xingchen Ye at Indiana University (USA) experimentally realized multiple phases of tetrahedron colloids where vertex sharpness, surface ligands, and the self-assembly environment play key roles in the formation of the quasicrystal and the dimer crystal. Our colleagues at the Institute of Micro- and Nanostructure Research at FAU resolved the complex three-dimensional structure of the quasicrystal by a combination of electron microscopy, tomography, and synchrotron X-ray scattering. The joint findings demonstrate the predictive power of computer simulations as well as the importance of accurate control over nanocrystal attributes and the assembly method to realize increasingly complex nanopolyhedron supracrystals.

Read about the research here:

Yi Wang, Jun Chen, Ruipeng Li, Alexander Götz, Dominik Drobek, Thomas Przybilla, Sabine Hübner, Philipp Pelz, Lin Yang, Benjamin Apeleo Zubiri, Erdmann Spiecker, Michael Engel, Xingchen Ye
Controlled Self-Assembly of Gold Nanotetrahedra into Quasicrystals and Complex Periodic Supracrystals
Journal of the American Chemical Society 145, 17902 (2023)

The following Saturday,

Oct 19, 2019, 18h–1h, in the foyer of IZNF (Cauerstraße 3)

our lab will participate at Lange Nacht der Wissenschaften, an established form of public relations activity in Germany. We will present our work in form of interactive particle simulations, 3d visualizations, and a small hands-on experiment involving a laser interacting with a colloidal monolayer.

Kommen Sie uns besuchen!

EngelLab Group poster
EngelLab Group poster (in German).
A high-resolution version can be viewed by clicking on the image.

Our joint work with Nicolas Vogel and Erdmann Spiecker advanced the understanding of the structure, defect accumulation and thermodynamics of colloidal clusters on and off magic numbers and was awarded this month’s cover for ACS Nano. Congratulations Junwei and Chrameh!

Read about it here:

Free Energy Landscape of Colloidal Clusters in Spherical Confinement
J. Wang, C.F. Mbah, T. Przybilla, S. Englisch, E. Spiecker, M. Engel, N. Vogel
ACS Nano 13, 9005-9015 (2019)

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)

EAM Science meets Fiction is a scientifically oriented exhibition that includes literature contributions. Our lab contributed one computer rendering of a clathrate crystal made from triangular bipyramids taken from a recent publication.

The exhibition takes place from Sept 16 to Oct 27 in the church “Kreuz+Quer, Haus der Kirche”, Bohlenplatz 1, 91054 Erlangen.