The tetrahedral framework in glasses and melts ? inferences from molecular orbital calculations and implications for structure, thermodynamics, and physical properties

Navrotsky, Alexandra; Geisinger, Karen L.; McMillan, Paul F.; Gibbs, G. V.

doi:10.1007/bf00307406

Cited by 213 publications

(95 citation statements)

References 76 publications

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“…The relative values of heats of solution (H,,) provide information on the relative strengths of bonds broken during the dissolution process. The values of H,, become more exothermic with increasing cation electronegativity (from K to Mg) and, as noted by NAVROTSKY et al (1985). the decrease in average bond strength, inferred from more exothermic values of H,,, correlates with decreasing viscosities for these compositions.…”

Section: Enthalpy Of Solutionmentioning

confidence: 57%

“…Related information for a hypothetical tectosilicate structure of melts on the Si02-NaB02 join comes from the ab initio molecular orbital calculations of GEISINGER et al (1985). NAVROTSKY et al (1985) NAVROTSKY et al ( 1985) suggest that the lower value of T-O-T bond angle and the relative "inflexibility" of this angle for bonds involving B3+ rather than A13+ poses a potential energy barrier to the substitution of borate for silicate tetrahedra in borosilicate melts.…”

Section: T-o-t Bond Angle Variationmentioning

confidence: 99%

“…NAVROTSKY et al (1985) NAVROTSKY et al ( 1985) suggest that the lower value of T-O-T bond angle and the relative "inflexibility" of this angle for bonds involving B3+ rather than A13+ poses a potential energy barrier to the substitution of borate for silicate tetrahedra in borosilicate melts.…”

Section: T-o-t Bond Angle Variationmentioning

confidence: 99%

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Viscosities of melts in the Na2OFeOFe2O3SiO2 system and factors controlling relative viscosities of fully polymerized silicate melts

Dingwell

Virgo

1988

Geochimica et Cosmochimica Acta

122

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Abstract-The viscosity-temperature relationships of nine melts in the NazO-FeO-Fe20&iO~ system (in equilibrium with air) have been measured in the temperature range of 145&800"C, using the concentric cylinder method. "Fe Miissbauer spectra were obtained on quenched samples and show that all melts with 220 mole% ferrite component contain ~95% Fe as tetrahedrally-coordinated ferric ions.The compositions investigated lie along the Sit&NaFe@ and NarSi,Os-NqFe.09 joins. The viscosities of melts decrease strongly with decreasing silicate content along these joins. In contrast. the temperature dependence of viscosity does not vary significantly along these joins.Comparison with equivalent melt compositions (related by the trivalent cation exchange operators AIFe_, , BFe_, and GaFe-,) in the Na20-Al201-SiOa, NarO-BaOTSi02 and Na#-Ga,0rSi02 systems, shows that viscosities decrease in the order aluminosilicate > ferrosilicate, (galliosilicate ?) > borosilicate.The electronegativities of the trivalent cations are inversely correlated with the relative viscosities of melts in these systems. Similarly. the electronegativities of network-stabilizing cations are inversely correlated with melt viscosity for alkali and alkaline-earth aluminosilicate melt systems. The variation in the viscosity of tectosilicate melts is correlated with estimated average T-O-T bond angles. and exothermic heats of solution of quench glasses. Structural controls of viscosity discussed are tetrahedral ordering and relative bond strengths.The acmite comnonent in natural. peralkaline, silicic volcanics will not contribute directly to high melt viscosities for these lavas.. VtsCosrTY IS PERHAPS the single most important physical property of magmas (and lavas) (WILLIAMS and MCBIRNEY. 1979; FISHER and SCHMINKE, 19843. For relatively dry, crystal-poor, peralkaline lavas such as those of the Kenya rift zone (BAILEY and MACDONALD, 1987) the determination of lava viscosity during eruptions is iargely a question of estimating '1) the temperature of eruption, and 2) the temperature-viscosity relationship of the erupted silicate melts whose compositions are probably very similar to the com~sitions of the glassy peralkaline rocks.One of the most diagnostic chemical expressions of peralkalinity in the Kenyan comendites, trachytes and pantelIerites is the presence of CIPW-normative acmite. Estimation of the eruptive viscosities of these Iavas is. therefore, hindered by the lack ofdata for the viscosity-tem~rature relationships in the system NazO-FeO-Fe*O,-SiOz, particularly for the acmite component. In fact, as noted by E~XTINGA and WEILL ( 1972). there is a paucity of viscosity data for highly oxidized iron-~a~ng silicate melts.A comparison of the viscosity-temperature relationships of ferric iron-and aluminum-bearing melts may provide further insight into the relationship between melt viscosity and melt structure because (like aluminum in the Na20-A&O,-SiO1 system) ferric iron appears to be in tetrahedral coordination in melts in the Na20-FeO-Fe203-Sit& system th...

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Section: Enthalpy Of Solutionmentioning

confidence: 57%

Section: T-o-t Bond Angle Variationmentioning

confidence: 99%

See 1 more Smart Citation

Viscosities of melts in the Na2OFeOFe2O3SiO2 system and factors controlling relative viscosities of fully polymerized silicate melts

Dingwell

Virgo

1988

Geochimica et Cosmochimica Acta

122

View full text Add to dashboard Cite

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“…In contrast, the SiOSi angles exhibited large variations, accounting probably for the polymorphism of the crystalline silica. According to the MO calculations, nonframework ions of smallest size and largest charge have the largest perturbation e!ect; therefore, Li'Na'K'Cs (21). Indeed, lithium and sodium are able to lower to 1073 K the transition temperature of amorphous to crystalline phase even when present in a small amount, about 0.4 mmol/g.…”

Section: Discussionmentioning

confidence: 99%

Effect of Alkali Ions on the Amorphous to Crystalline Phase Transition of Silica

Venezia¹,

Parola

Longo³

et al. 2001

Journal of Solid State Chemistry

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“…The presence of divalent cations and the coupling of Al tetrahedral therefore imposes a strain in the network which facilitates its breakdown at high temperature, causing fragile behavior (Scamehorn and Angell, 1991). An increase of Al with respect to Si has a similar effect of lengthening TO bonds and decreasing TOT bond angle, thus destabilizing the network Navrotsky et al, 1985). Moreover, it has been shown that both an increase of Al/Si ratio and Ca + Mg/Na + K ratio can increase the chemical contribution to the configurational heat capacity via an increase in Q species disorder (Mysen, 1997;Neuville, 2006;Cheng et al, 2012).…”

Section: Configurational Heat Capacity Of Hydrous Magmasmentioning

confidence: 99%

Heat capacity, configurational heat capacity and fragility of hydrous magmas

Genova

Romano

Giordano

et al. 2014

Geochimica et Cosmochimica Acta

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International audienceThe glassy and liquid heat capacities of four series of dry and hydrous natural glasses and magma as a function of temperature and water content (up to 19.9 mol%) were investigated using differential scanning calorimetry (DSC). The analyzed compositions are basalt, latite, trachyte and pantellerite. The results of this study indicate that the measured heat capacity of glasses (Cpg) is a linear function of composition and is well reproduced by the empirical model of Richet (1987). For the investigated glasses, the partial molar heat capacity of water can be considered as independent of composition, in agreement with Bouhifd et al. (2006). For hydrous liquids, the heat capacity (Cpliq) decreases nonlinearly with increasing water content. Previously published models, combined with the partial molar heat capacity of water from the literature, are not able to reproduce our experimental data in a satisfactory way. We estimated the partial molar heat capacity of water (CpH2O) in hydrous magma over a broad compositional range. The proposed value is 41 ± 3 J mol-1 K-1. Water strongly affects the configurational heat capacity at the glass transition temperature [Cpconf (Tg)]. An increases of Cpconf (Tg) with water content was measured for the polymerized liquids (trachyte and pantellerite), while the opposite behavior was observed for the most depolymerized liquids (basalt and latite). Structural and rheological implications of this behavior are discussed in light of the presented results

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The tetrahedral framework in glasses and melts ? inferences from molecular orbital calculations and implications for structure, thermodynamics, and physical properties

Cited by 213 publications

References 76 publications

Viscosities of melts in the Na2OFeOFe2O3SiO2 system and factors controlling relative viscosities of fully polymerized silicate melts

Viscosities of melts in the Na2OFeOFe2O3SiO2 system and factors controlling relative viscosities of fully polymerized silicate melts

Effect of Alkali Ions on the Amorphous to Crystalline Phase Transition of Silica

Heat capacity, configurational heat capacity and fragility of hydrous magmas

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