The medium range order (MRO) in amorphous systems has been linked to complex features such as the dynamic heterogeneity of supercooled liquids or the plastic deformation of glasses. However, the nature of the MRO in these materials has remained elusive, primarily due to the lack of methods capable of characterizing this order. Here, we leverage standard two-body structural correlators and advanced many-body correlation functions to probe numerically the MRO in prototypical network glassformers, i.e., silica and sodium silicates, systems that are of importance in natural as well as industrial settings. With increasing Na concentration, one finds that the local environment of Na becomes more structured and the spatial distribution of Na on intermediate length scales changes from blob-like to channel-like, indicating a growing inhomogeneity in the spatial Na arrangement. In parallel, we find that the Si-O network becomes increasingly depolymerized, resulting in a ring size distribution that broadens. The radius of gyration of the rings is well described by a power-law with an exponent around 0.75, indicating that the rings are progressively more crumbled with increasing size. Using a recently proposed four-point correlation function, we reveal that the relative orientation of the tetrahedra shows a transition at a distance around 4 Angstroms, a structural modification that is not seen in standard two-point correlation functions. Furthermore, we find that the length scale characterizing the MRO is non-monotonic as a function of temperature, caused by the competition between energetic and entropic terms. Finally, we demonstrate that the structural correlation lengths as obtained from the correlation functions that quantify the MRO are correlated with macroscopic observables such as the kinetic fragility of the liquids and the elastic properties of the glasses.
Microscopic mechanism of structural and volume relaxation below glass transition temperature in a soda-lime silicate glass revealed by Raman spectroscopy and its first principle calculations
Revealing the Void-Size Distribution of Silica Glass using Persistent Homology
Federal Institute of Materials Research and Testing（联邦材料研究与测试研究所）；Sultan Moulay Slimane University of Beni Mellal（贝尼梅拉勒苏丹穆莱·斯莱曼大学）；RWTH Aachen University（亚琛工业大学）
Boson peak and medium-range elastic heterogeneity in calcium silicate hydrate probed by terahertz spectroscopy and low-temperature calorimetry
College of Architecture and Civil Engineering, Beijing University of Technology（北京工业大学建筑与土木工程学院）；Dalian Institute of Chemical Physics, Chinese Academy of Sciences（中国科学院大连化学物理研究所）；School of Environment and Safety Engineering, North University of China（中北大学环境与安全工程学院）；Department of Civil Engineering, Taiyuan University of Technology（太原理工大学土木工程学院）；State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所非线性力学国家重点实验室）；School of Materials Science and Engineering, Southeast University（东南大学材料科学与工程学院）；College of Civil and Transportation Engineering, Shenzhen University（深圳大学土木与交通工程学院）；Faculty of Innovation Engineering, Macau University of Science and Technology（澳门科技大学创新工程学院）
