Designing quasicrystalline ground states of colloids: An inverse statistical-mechanics approach

• Applicant: Dr. Erdal Celal Oguz
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2014 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 256871717

Quasicrystals are materials possessing rotational symmetry but lacking periodicity. Since their discovery in 1982, quasicrystals have not only drawn big attention in the scientific community due to their sophisticated material properties such as low surface friction and high rigidity, they have also led to many fruitful interdisciplinary interactions between scientist from physics, chemistry and mathematics. Almost all observed quasicrystals are found in metallic alloys so far. Meanwhile, soft quasicrystals built with colloids or polymer micelles constituents are in the focus of recent studies. A big advantage of studying colloidal quasicrystals is that individual particle positions are directly observable, e.g., by using video-microscopy. Importantly, a theoretical explanation of the stability or a prediction of the self-assembly process of colloidal quasicrystals remains a challenging task to date. It is still an open question which intramolecular forces are needed to obtain an intrinsic (not induced from outside) quasicrystal. The project at hand claims to close this gap by investigating the ground-state stability of quasicrystals. Particularly, it is planned to apply the inverse statistical-mechanical techniques to construct interaction potentials that minimise the potential energy, and hence, that spontaneously lead to quasicrystalline ordering at zero temperature. The results will not only enlighten the stability of quasicrystals, they will also essentially contribute to the fundamental understanding of the relation between the structure and the intramolecular interactions in a quasicrystalline system. Beyond that, this project will open the way of enabling quasicrystalline self-assembly in colloid experiments by tailoring the experimental interaction potentials toward our findings. Moreover, in a late stage of this project, the degree of spatial order in quasicrystals shall be quantified by using the concepts of the local density fluctuations in many-particle systems. As a consequence, statements can be made about the relation between the spatial order and the internal properties, such as rotational symmetries or incommensurate length scales of a quasicrystalline system.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Salvatore Torquato, Ph.D.