Benjamim John Albert Moulton

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.

A glass series with constant ∼30 mol% BaO in the BaO–B ₂ O ₃ –SiO ₂ system was studied as a function of SiO ₂ /B ₂ O ₃ ratio. This system has been studied in‐depth to reveal the structure, Part 1, and its relationship to the mechanical properties, Part 2. Both the B coordination and network polymerization are quantified both experimentally, using Raman, IR, and ¹¹ B NMR spectroscopies, and theoretically, using classical molecular dynamics (MD) simulations with effective partial charge potentials with composition dependent boron parameters. These results show that ^III B, threefold‐coordinated boron, increases linearly with increasing boron, at the expense of ^IV B. The Q ³ equilibrium constant decreases slightly with boron addition up to 37 mol%, whereas at greater B ₂ O ₃ contents, the silica tetrahedra become more polymerized. These trends are reinforced by MD simulation results, which show that the average connectivity, polymerization, and ring size are directly related. The glass transition temperature increases with increasing silica content, where the range of temperatures follows the packing density. The BaO–B ₂ O ₃ –SiO ₂ system shows systematic trends from high to low oxygen packing between the binary borate glasses to the binary silicate glasses, indicating a high degree of predictability for properties controlled by density.

Connectivity of the Al–O networks in R ₃ Al ₅ O ₁₂ melts (R = La or Yb) are compared and correlated with their glass forming abilities. A new connectivity metric, K ⁿ , is defined to account for ^[5] Al network units, edge-sharing, and triply bonded oxygen.

XPS spectra of lithium tetraborate (Li2B4O7) were obtained using an Al Kα (1486.6 eV) source and a quartz (1010) crystal monochromator through first-order diffraction. Irradiation occurs on the sample at 54.7° to the surface normal. Spectra of the principal lines include O 1s, C 1s, B 1s, and Li 1s. Spectra of O KLL and O 2s and valence band were also acquired.

XPS spectra of lithium tetraborate (Li2B4O7) were obtained using an Ag Lα (2984.3 eV) source and a quartz (1010) crystal monochromator through second order diffraction. Irradiation occurs on the sample at 54.7° to the surface normal. Spectra of the principal lines include O 1s, C 1s, B 1s and Li 1s. Spectra of O KLL, O 2s and Valence band were also acquired. Quantitative analysis was performed using Cant sensitivity factors.

This work aimed to explore the effect of high pressures at room temperature on the vibrational modes and the thermal properties and stability of barium disilicate glass (BaO‐2SiO ₂ ) (BS2). The BS2 was prepared through the conventional melting route at atmospheric pressure. After being submitted to different pressure values (2.5 GPa, 4.0 GPa, and 7.7 GPa) and room temperature, the samples were characterized ex situ by Raman spectroscopy and differential thermal analysis. With this, it is possible to see that the pressure modifies the Raman vibrational modes of the glass, in the region associated with the Si‐O‐Si symmetrical bending modes. The Si‐O symmetrical stretching vibrational modes (Q ⁿ ) remain unchanged, however there are changes on values of glass transition and decrease crystallization temperature, as well as the parameters of thermal stability of the glass.