Viscosity-temperature relations and structure in fully polymerized aluminosilicate melts from ion dynamics simulations

Journal Article · Fri Mar 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90336-4· OSTI ID:6033465

Scamehorn, C A; Angell, C A ^[1]

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1. Arizona State Univ., Tempe (United States)

Results of a series of molecular dynamics simulations indicate that the Al:Si ratio present in aluminosilicate melts induces a chemical pressure that significantly influences the temperature dependence of the melt viscosity. The temperature dependence of the T-O bond length and T-O-T angle in the melt has been calculated for albite, anorthite, nepheline, and MgAl{sub 2}Si{sub 2}O{sub 8} (a magnesium analog of anorthite) at their experimental melt densities at atmospheric pressure and for pure silica at two different densities corresponding to V/V{sub 0} = 1.0 (1atm) and V/V{sub 0} = 0.8 ({approximately}4 GPa). These simulations show that melt fragility can be correlated to increasing T-O length and decreasing T-O-T angle, both of which are characteristics of silicate melts under increasing pressure. Framework cations with coordination numbers greater than four are observed in these aluminosilicate melts and are shown to be related to fragile behavior. Finally, for nepheline and anorthite we infer a large contribution to fragility from configurational disordering of Al-O-Si links which are known to be dominant in the glasses but are found to be absent from the simulated melts.

• OSTI ID: 6033465
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:3; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
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58 GEOSCIENCES
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ALBITE
ANORTHITE
BOND LENGTHS
CHARGED PARTICLES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
DIMENSIONS
FELDSPARS
FLOW MODELS
FLUID FLOW
GEOCHEMISTRY
GEOTHERMAL SYSTEMS
IGNEOUS ROCKS
ION EXCHANGE
IONS
LENGTH
MAGMA
MAGMA SYSTEMS
MATHEMATICAL MODELS
MINERALS
MOLECULAR STRUCTURE
NEPHELINE BASALTS
OXYGEN IONS
PARTICLE MODELS
POLYMERIZATION
ROCKS
SILICATE MINERALS
SILICON IONS
STATISTICAL MODELS
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE EFFECTS
THERMODYNAMIC MODEL
VISCOSITY
VISCOUS FLOW
VOLCANIC ROCKS