Entropy of Liquids and Glasses from Recurring Structural Patterns

Abstract

We compute the low-temperature configurational entropy of a two-dimensional supercooled liquid. Our method, based on a higher-dimensional version of the Grassberger--Procaccia algorithm, can be implemented in a manner that is entirely agnostic with respect to both the dynamics and the theoretical framework, as any genuine notion of order should be. In this construction, entropy is obtained as the decay rate of recurrent structural patterns with increasing patch size, directly linking entropy reduction to the growing persistence of amorphous order. Because the method requires only particle positions, without any knowledge of the interaction potential or even of the particle sizes, it can be applied directly to both equilibrium and nonequilibrium aging configurations. The resulting configurational entropy, together with the higher-order R\'enyi complexities, agree quantitatively with values obtained from conventional definitions. Remarkably, the entropies measured during aging coincide with their equilibrium counterparts when compared at the same inherent-structure energy.