Medium-range order in the cation distribution of a calcium silicate glass

Gaskell, Philip; Eckersley, M. C.; Barnes, Adrian C; Chieux, P.

doi:10.1038/350675a0

Cited by 251 publications

(151 citation statements)

References 8 publications

Supporting

Mentioning

123

Contrasting

Unclassified

Order By: Relevance

“…The structure of the glass at a composition close to CaSiO 3 ͑with the addition of 3% Al 2 O 3 ͒ has been studied in exceptional detail using a double difference neutron isotopic substitution method. 4 Gaskell et al 4 provided evidence that the distribution of calcium atoms was not random in the glass but exhibited a well-defined Ca-Ca peak at 3.8 Å bearing many characteristics of the crystalline form. The structures of crystalline pyroxenes such as wollastonite can be considered as a close packed oxygen sublattice with Ca occupying octahedral interstices in alternate layers in a fcc model.…”

Section: Resultsmentioning

confidence: 99%

“…2,3 This is despite the analysis of quenched glass structures that indicate atomic to nanometer scale structural heterogeneity must occur in the liquid state. [4][5][6][7] Silica is classified as a strong liquid with an Arrhenius viscosity-temperature relation and only subtle differences occur between the liquid and glass structures. 8,9 In contrast CaO-SiO 2 liquids can be considered fragile based on viscosity measurements 10,11 and consequently larger structural rearrangements are likely to be necessary to form a glass.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Temperature-dependent structural heterogeneity in calcium silicate liquids

et al. 2010

View full text Add to dashboard Cite

X-ray diffraction measurements performed on aerodynamically levitated CaSiO 3 droplets have been interpreted using a structurally heterogeneous liquid-state model. When cooled, the high-temperature liquid shows evidence of the polymerization of edge shared Ca octahedra. Diffraction isosbestic points are used to characterize the polymerization process in the pair-distribution function. This behavior is linear in the hightemperature melt but exhibits rapid growth just above the glass transition temperature around 1.2T g . The heterogeneous liquid interpretation is supported by molecular-dynamics simulations which show the CaSiO 3 glass has more edge-shared polyhedra and fewer corner shared polyhedra than the liquid model.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Temperature-dependent structural heterogeneity in calcium silicate liquids

et al. 2010

View full text Add to dashboard Cite

show abstract

“…A similar argument can be made for minerals crystallizing from magmas. For example, Gaskell et al (1991) showed that a glass of composition CaSiO 3 has a local structure very similar to that of wollastonite. Assuming that the structure of the glass is somewhat similar to that of CaSiO 3 melt close to the liquidus, the initial reactant in the crystallization of wollastonite (a CaSiO 3 ''magma'') is already templated with much of the wollastonite structure, and many of the atoms in the system will obey the Reaction Principle, resulting in the crystallization of wollastonite.…”

Section: Fourth-moment Changesmentioning

confidence: 99%

A bond-topological approach to theoretical mineralogy: crystal structure, chemical composition and chemical reactions

Hawthorne

2012

Phys Chem Minerals

View full text Add to dashboard Cite

Here, I describe a theoretical approach to the structure and chemical composition of minerals based on their bond topology. This approach allows consideration of many aspects of minerals and mineral behaviour that cannot be addressed by current theoretical methods. It consists of combining the bond topology of the structure with aspects of graph theory and bond-valence theory (both long range and short range), and using the moments approach to the electronic energy density-of-states to interpret topological aspects of crystal structures. The structure hierarchy hypothesis states that higher bond-valence polyhedra polymerize to form the (usually anionic) structural unit, the excess charge of which is balanced by the interstitial complex (usually consisting of large low-valence cations and (H 2 O) groups). This hypothesis may be justified within the framework of bond topology and bond-valence theory, and may be used to hierarchically classify oxysalt minerals. It is the weak interaction between the structural unit and the interstitial complex that controls the stability of the structural arrangement. The principle of correspondence of Lewis acidity-basicity states that stable structures will form when the Lewis-acid strength of the interstitial complex closely matches the Lewis-base strength of the structural unit, and allows us to examine the factors that control the chemical composition and aspects of the structural arrangements of minerals. It also provides a connection between a structure, the speciation of its constituents in aqueous solution and its mechanism of crystallization. The moments approach to the electronic energy densityof-states provides a link between the bond topology of a structure and its thermodynamic properties, as indicated by correlations between average anion coordination number and reduced enthalpy of formation from the oxides for [6]

show abstract

“…The wave vector Q, of the FSDP corresponds to a length scale L, = 2x/Q, on the order of 2.5 r, (rl is the nearest-neighbor distance in the glass), greater than the dimensions of the nominal building blocks of the glasses [8,9]. Recently, the nature and origin of extendedrange order, corresponding to a correlation length Lo that is greater than that of the intermediaterange order and characterized by a diffraction peak in S(Q) at lower wave vector than the FSDP, was probed in alkali germanate glasses using a combination of anomalous X-ray scamkg (AXS) and neutron diffraction (ND) [ 10,113. Spectroscopic tools such as EXAFS and NMR have proved successful for investigating the cation surroundings and network structure, respectively.…”

Section: *mentioning

confidence: 99%