Soft matter quasicrystals: when can they exist and when will we observe them?

Mathematician, Dr Priya Subramanian joins us from Oxford University to talk about her research to our Soft Matter Physics Research Group.

Abstract: Regular patterns (made of tiles) and crystals (made of either atoms/molecules) surround us in everyday life. These patterns look the same when moved by one unit (translational symmetry) or rotated by certain special angles (rotational symmetry). Such repeating arrangements are prevalent in nature as lesser amount of energy is required to assemble them. Aperiodic patterns or quasicrystals are special as they possess long range order without translational symmetry. Quasicrystals have recently been observed in a variety of systems such as nanoparticles, metallic alloys and polymer solutions. Considering the difference in scale between metallic and polymeric quasicrystals, there is a need for mathematical models which explore unifying mechanisms. We begin by exploring phase field crystal models to identify the ingredients that allow for the formation of soft matter quasicrystals. We then go on to a more realistic density functional theoretic model, where we identify features in the particle pair interaction potentials which can enable either the enhancement or suppression of thermodynamically stable quasicrystals. Finally we show that adopting a new representation to describe the density distribution allows us to accurately compute phase diagrams for soft matter systems at reduced computational expense.

Host: Dr Mamatha Nagaraj

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