Microscopically-resolved simulations prove the existence of soft cluster crystals

TL;DR

This study uses detailed simulations of amphiphilic dendritic macromolecules to confirm the existence of stable soft cluster crystals, revealing key properties and limitations due to steric effects.

Contribution

It provides the first microscopic validation of cluster crystals predicted by effective pair potentials, highlighting their properties and density limits.

Findings

Cluster crystals are stable and form at various densities.

Site occupancy adjusts with density and defects can be healed.

Steric crowding imposes an upper density limit for crystal stability.

Abstract

We perform extensive monomer-resolved computer simulations of suitably-designed amphiphilic dendritic macromolecules over a broad range of densities, proving the existence and stability of cluster crystals formed in these systems, as predicted previously on the basis of effective pair potentials [B. M. Mladek et al., Phys. Rev. Lett. 96, 045701 (2006)]. Key properties of these crystals, such as the adjustment of their site occupancy with density and the possibility to heal defects by dendrimer migration, are confirmed on the monomer-resolved picture. At the same time, important differences from the predictions of the pair potential picture, stemming from steric crowding, arise as well and they place an upper limit in the density for which such crystals can exist.