Connectedness and Linkedness of Non‐Zachariasen Oxide Networks

Connectedness and linkedness quantify the structural arrangement of cation─oxygen polyhedra in oxide materials and have a direct impact on mechanical and other properties. The application of these structural descriptors is well‐established for glasses whose structures follow Zachariasen's rules, but standardized methodologies for connectedness and linkedness analyses are lacking for non‐Zachariasen networks. These unusual oxide glasses are characterized by cation─oxygen polyhedra with coordination numbers above four, substantial edge‐sharing among network polyhedra, and oxygen atoms linking three network‐forming units. Here, we describe an approach and associated algorithm to non‐Zachariasen network analysis (NZNA) that calculates connectedness and linkedness for any oxide glass or crystal structure. We implement this approach in an open‐source Python package, nznet . NZNA is first benchmarked against a variety of crystal structures (e.g., tridymite, sillimanite, andalusite, kyanite, and grandidierite) as well as archetypal sodium silicate glasses, and then applied to 62Al 2 O 3 ‐38SiO 2 (AS62) glass as a case study. In AS62, the connectedness of network units ranges from five to nine neighboring units, and linkages among AlO 5 units are over 40% edge‐sharing. The bond valence sums of the network formers, also calculated by nznet , indicate that SiO 4 units are underbonded and that the valence sums have a slightly negative correlation with connectedness. These examples illustrate how NZNA unambiguously analyzes and reports these structural descriptors, which enables direct comparison of both Zachariasen and non‐Zachariasen glass networks alike, as well as the correlation of properties with their intermediate‐range order.