Structural Diversity in Condensed Matter: A General Characterization of Crystals, Amorphous Solids and the Structures Between

TL;DR

This paper introduces a general measure of structural diversity for condensed matter, effectively distinguishing between crystalline, amorphous, and intermediate structures, and demonstrating its use as an order parameter for structural transitions.

Contribution

It adapts a biodiversity-inspired diversity measure to characterize condensed matter structures, revealing intermediate states and organizing structural changes.

Findings

Diversity measure filters noise and differentiates structures

Identification of intermediate structures between crystals and glasses

Diversity as an order parameter for structural transitions

Abstract

A definition of structural diversity, adapted from the biodiversity literature, is introduced to provide a general characterization of structures of condensed matter. Using the Favored Local Structure (FLS) lattice model as a testbed, the diversity measure is found to effectively filter extrinsic noise and to provide a useful differentiation between crystal and amorphous structures. We identify an interesting class of structures intermediate between crystals and glasses that are characterised by a complex combination of short-range ordering and long-range disorder. We demonstrate how the diversity can be used as an order parameter to organise various scenarios by structure change in response to increasing diversity.