Toward generating colloidal cubic phases: Shape sensitivity of the Ia(-3)d gyroid phase in hard pear-shaped particle systems

The ambition to mimic highly complex and functional nanostructures found in living organisms marks one of the pillars of today's research in bio- and soft matter physics. Here, self-assembly has evolved into a prominent strategy in nanostructure formation. However, it is still a challenge to design and realise particle properties such that they self-organise into the desired target configuration. One key design parameter is the (effective) shape of the constituent particles.

We address the entropically driven colloidal self-assembly of tapered ellipsoids, reminiscent of "pear-shaped" particles, including the formation of structures based on triply periodic minimal surfaces (TPMS) such as the gyroid. Using computational simulations, we investigate the influence of variations in shape on the stability of the gyroid phase. We show that the formation of the gyroid reported earlier in the so-called pear hard Gaussian overlap (PHGO) approximation, is due to small non-additive properties of that potential. This phase does not form in pears with a "true" hard pear-shaped potential. In particular, the slight differences in shape favour the formation of interdigitated bilayers in the PHGO particle ensemble, which indicates a two-step hierarchical mechanism to generate TPMS phases.