Encyclopedia of Glass Science, Technology, History, and Culture. Группа авторов

by observed increases in Al/Si disorder in glasses with higher fictive temperatures, making a larger contribution to configurational heat capacity. Subsequent extensive work on high‐pressure aluminosilicates has begun to elucidate the much more complex linkages among not only tetrahedral network species but five‐ and six‐coordinated Al and Si, where the mixing of all of these network species presumably contributes to increases in configurational entropy [16].

      The same experimental approach can, in some borosilicate glass compositions, quantify the extent of mixing of boron and silicon network cations, which can be much greater than considered in early models based primarily on ¹¹B NMR data (Figure 3). In compositions with modifier oxides, the structure is further complicated by the presence of both BO₃ and BO₄ groups. As for aluminosilicates, relatively highly charged B–O–B linkages between two of the latter seem to be at least partially “avoided.” When pairs of network cations are present that can have strong nuclear dipolar couplings, notably ¹¹B and ²⁷Al, or ²⁷Al and ³¹P, double‐resonance NMR methods can reveal their relative proximities and even the correlations of species with multiple coordination environments, for example of BO₃ groups with AlO₄ [17]. These findings again can provide important constraints on mixing and contributions to order/disorder.

8 Perspectives

Technical advances continue to increase the quality, depth, and breadth of information that can be obtained about short‐range structure and order in oxide glasses, for example, microscale XAS, X‐ray Raman, improved neutron scattering facilities, and NMR at higher magnetic fields and with methods that allow better measurements of internuclear distances and connectivities. Combination of experimental data from different methods, to yield consistent models, is especially powerful, as illustrated in Figure 7 [18]. Some of these approaches are now feasible for in‐situ studies of high‐temperature liquids and even of liquids at high pressure and temperature. Advances in theory are beginning to allow accurate forward calculation of spectra (e.g. vibrational and NMR) from structural models [19]. This information can then be combined with experimental data to obtain much more complete views of structure, quantitative extent of disorder, and their links to thermodynamic properties that depend critically on configurational entropy, such as viscosity, heat capacity, and the bulk free energy. As researchers move beyond model‐dependent fitting and interpretation of spectra of glasses to more complete theoretical analyses, our understanding of the true complexities of these fascinating and useful materials will expand enormously.

Figure 7 Partial pair distribution functions g_ij(r) calculated from a “reverse Monte Carlo” model combining X‐ray and neutron diffraction data for various CaSiO₃–MgSiO₃ glasses.

      Source: Reprinted with permission from [18].

References

      1 1 Greaves, G.N. and Sen, S. (2007). Inorganic glasses, glass‐forming liquids and amorphizing solids. Adv. Phys. 56: 1–166.

      2 2 Mysen, B.O. and Richet, P. (2018). Silicate Glasses and Melts, 2e. Amsterdam: Elsevier.

      3 3 Kroeker, S.K., Rice, D., and Stebbins, J.F. (2002). Disordering during melting: an oxygen‐17 NMR study of crystalline and glassy CaTiSiO5 (titanite). Am. Mineral. 87: 572–579.

      4 4 Warren, B.E. and Biscoe, J. (1938). Fourier analysis of X‐ray patterns of soda‐silica glass. J. Am. Ceram. Soc. 21: 259–265.

      5 5 Stebbins, J.F. (2016). Glass structure, melt structure and dynamics: some concepts for petrology. Am. Mineral. 101: 753–768.

      6 6 Stebbins, J.F. (2017). “Free” oxide ions in silicate melts: thermodynamic considerations and probable effects of temperature. Chem. Geol. 461: 2–12.

      7 7 Stebbins, J.F. and Poe, B.T. (1999). Pentacoordinate silicon in high‐pressure crystalline and glassy phases of calcium disilicate (CaSi2O5). Geophys. Res. Lett. 26: 2521–2523.

      8 8 Silver, A.H. and Bray, P.J. (1958). Nuclear magnetic resonance absorption in glass. 1. Nuclear quadrupolar effects in boron oxide, soda‐boric oxide, and borosilicate glass. J. Chem. Phys. 29: 984–990.

      9 9 Wu, J. and Stebbins, J.F. (2013). Temperature and modifier cation field strength effects on aluminoborosilicate glass network structure. J. Non‐Cryst. Solids 362: 73–81.

      10 10 Bista, S., Stebbins, J.F., Wu, J., and Gross, T.M. (2017). Structural changes in calcium aluminoborosilicate glasses recovered from pressures of 1.5 to 3.0 GPa: Interactions of two network species with coordination number increases. J. Non‐Cryst. Solids 478: 50–57.

      11 11 Neuville, D.R., Cormier, L., and Massiot, D. (2006). Al coordination and speciation in calcium aluminosilicate glasses: effects of composition determined by Al‐27 MQ‐MAS NMR and Raman spectroscopy. Chem. Geol. 229: 173–185.

      12 12 Brown, G.E. Jr., Farges, F., and Calas, G. (1995). X‐ray scattering and x‐ray spectroscopy studies of silicate melts. In: Structure, Dynamics, and Properties of Silicate Melts (eds. J.F. Stebbins, P.F. McMillan and D.B. Dingwell), 317–410. Washington, DC: Mineralogical Soc iety of America.

      13 13 Eckert, H. (1994). Structural studies of non‐crystalline solids using solid state NMR. New experimental approaches and results. In: Solid‐State NMR IV. Methods and Applications of Solid‐State NMR (ed. B. Blümich), 127–202. Berlin: Springer‐Verlag.

      14 14 Galoisy, L. (2006). Structure‐property relationships in industrial and natural glasses. Elements 2: 293–297.

      15 15 Davis, M.C., Sanders, K.J., Grandinetti, P.J. et al. (2011). Structural investigations of magnesium silicate glasses by 29Si 2D magic‐angle flipping NMR. J. Non‐Cryst. Solids 357: 2787–2795.

      16 16 Lee, S.K., Fei, Y., Cody, G.D., and Mysen, B.O. (2003). Order and disorder in sodium silicate glasses and melts at 10 GPa. Geophys. Res. Lett. 30: 1845–1849.

      17 17 Chan, J.C.C., Bertmer, M., and Eckert, H. (1999). Site connectivities in amorphous materials studied by double‐resonance NMR of quadrupolar nuclei: high resolution 11B – 27Al spectroscopy of aluminoborate glasses. J. Am. Chem. Soc. 121: 5238–5248.

      18 18 Cormier, L. and Cuello, G.J. (2013). Structural investigation of glasses along the MgSiO3‐CaSiO3 join: diffraction studies. Geochim. Cosmochim. Acta 122: 498–510.

      19 19 Angeli, F., Villain, O., Schuller, S. et al. (2011). Insight into sodium silicate glass structural organization by multinuclear NMR combined with first‐principles calculations. Geochim. Cosmochim. Acta 75: 2453–2469.

      Note

      1 Reviewers:G.H. Henderson, Department of Earth Sciences, University of Toronto, Toronto, Ontario, CanadaB.O. Mysen, Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC, USA

2.5 The Extended Structure of Glass

       George Neville Greaves

       Department of Metallurgy and Materials Science, University of Cambridge, Cambridge, UK

1 Introduction

      The structure of glass stretches from atomic dimensions and local short-range order (SRO), which is often similar to that of the crystalline state, through intermediate-range order