Shape-anisotropy-induced transitions of densest-packed structures in confined mixtures of circles and ellipses

Shape-anisotropy-induced transitions of densest-packed structures have been discovered for binary mixtures of circles and ellipses in parallel-slit confinement. A continuous increase in the aspect ratio of ellipses results in a crossover of densest-packed configurations, from structures composed of circles surrounded by ellipses, through an intermediate regime of phase-separated structures, to structures composed of ellipses surrounded by circles. Our findings conclude that the densest-packed structures of such systems are all ordered arrangements of particles with minimal excess-volume effects from grain-boundary-like pairs of dissimilar particles.