Entropy favors heterogeneous structures of networks near the rigidity threshold

• Published in: Nature communications 2018-04, Vol.9 (1), p.1359-8, Article 1359
• Main Author: Yan, Le
• Format: Article
• Language: English
• Subjects: 639/766/119/1002; 639/766/530/2795; Amorphous materials; Elasticity; Entropy; Heterogeneity; Humanities and Social Sciences; multidisciplinary; Networks; Rigidity; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-03859-9

The dynamical properties and mechanical functions of amorphous materials are governed by their microscopic structures, particularly the elasticity of the interaction networks, which is generally complicated by structural heterogeneity. This ubiquitous heterogeneous nature of amorphous materials is intriguingly attributed to a complex role of entropy. Here, we show in disordered networks that the vibrational entropy increases by creating phase-separated structures when the interaction connectivity is close to the onset of network rigidity. The stress energy, which conversely penalizes the heterogeneity, finally dominates a smaller vicinity of the rigidity threshold at the glass transition and creates a homogeneous intermediate phase. This picture of structures changing between homogeneous and heterogeneous phases by varying connectivity provides an interpretation of the transitions observed in chalcogenide glasses. The mechanical and thermodynamic properties of amorphous materials are governed by their disordered network at microscales, but the detail remains elusive. Yan shows that the vibrational entropy induces a floppy-rigid phase separation near the rigidity onset and thus favors heterogeneous structures.