Packing of Soft Asymmetric Dumbbells

Abstract

We use numerical simulations to study the phase behavior of a system of purely repulsive soft dumbbells as a function of size ratio of the two components and their relative degree of deformability. We find a plethora of different phases which includes most of the mesophases observed in self-assembly of block copolymers, but also crystalline structures formed by asymmetric, hard binary mixtures. Our results detail the phenomenological behavior of these systems when softness is introduced in terms of two different classes of inter-particle interactions: (a) the elastic Hertz potential, that has a finite energy cost for complete overlap of any two components, and (b) a generic power-law repulsion with tunable exponent. We discuss how simple geometric arguments can be used to account for the large structural variety observed in these systems, and detail the similarities and differences in the phase behavior for the two classes of potentials under consideration.

Phase diagram of hard snowman-shaped particles

“…This closely matches the results of Ref. 33. We note that the FCC* phase has a similar EOS at low densities to the αIrV phase (Fig.…”

“…The range of d values where NaCl phases are stable is roughly the same as the range of size ratios for which NaCl phases were observed to form spontaneously in Ref. 33. We also see that as d increases the NaCl phases become increasingly more stable with respect to the RC phases.…”

“…A recent study using molecular dynamics simulations of snowman-shaped particles with various soft potentials 33 showed that a NaCl crystal could spontaneously form under compression for diameter ratios below ∼0.41 as one approaches the hard-particle limit. Similarly, for large diameter ratios ( 0.95) FCC-like structures can form.…”

“…16,17 For intermediate diameter ratios, however, no crystalline structures spontaneously formed, possibly due to the potential crystal structures in this region being kinetically inaccessible. 33 In this paper, we use computer simulations to map out the phase diagram by evaluating the free energies of candidate crystalline structures which correspond to the close packed structures of binary hard-sphere mixtures. We take the structures found in Ref.…”

Synthesis and Characterization of Monodisperse Thermosensitive Dumbbell‐Shaped Microgels

“…The structure and photonic properties of crystals formed from dumbbells have been investigated theoretically21 and experimentally 26, 27. Moreover, asymmetric dumbbells with a finite degree of softness are predicted to exhibit a multitude of mesophases 28…”