Towards a general definition of gelation for adhesive hard-sphere dispersions

TL;DR

This paper proposes a universal definition of gelation in adhesive hard-sphere dispersions, linking it to rigidity percolation at an average of 2.4 bonds per particle, supported by computer simulations.

Contribution

It establishes a connection between gelation in colloids and the universal concept of rigidity percolation, providing a unified framework for understanding arrested states.

Findings

Gelation occurs at an average of 2.4 bonds per particle.

Rigidity percolation underpins the gelation transition.

Structural distributions reveal the topology of the critical gel state.

Abstract

One major goal in condensed matter physics is identifying the physical mechanisms that lead to arrested states of matter, especially gels and glasses. The complex nature and microscopic details of each particular system are relevant. However, from both scientific and technological viewpoints, a general, consistent and unified definition is of paramount importance. Through Monte Carlo computer simulations of states identified in experiments, we demonstrate that adhesive hard-sphere dispersions are the result of rigidity percolation with average number of bonds, $<n_b>$, equals to 2.4. This corresponds to an established mechanism leading to phase transitions in network-forming materials. Our findings connect the concept of critical gel formation in colloidal suspensions with short-range attractive interactions to the universal concept of rigidity percolation. Furthermore, the bond, angular and local distributions along the gelation line are explicitly studied in order to determine the topology of the structure of the critical gel state.