Chemical interactions and configurational disorder in silicate melts

G. Ottonello


The Thermodynamics of quasi-chemical and polymeric models are briefly reviewed. It is shown that the two
classes are mutually consistent, and that opportune conversion of the existing quasi-chemical parameterization
of binary interactions in MO-SiO2 joins to polymeric models may be afforded without substantial loss of precision.
It is then shown that polymeric models are extremely useful in deciphering the structural and reactive properties
of silicate melts and glasses. They not only allow the Lux-Flood character of the dissolved oxides to be
established, but also discriminate subordinate strain energy contributions to the Gibbs free energy of mixing
from the dominant chemical interaction terms. This discrimination means that important information on the
short-, medium- and long-range periodicity of this class of substances can be retrieved from thermodynamic
analysis. Lastly, it is suggested that an important step forward in deciphering the complex topology of the inhomogeneity
ranges observed at high SiO2 content can be performed by applying SCMF theory and, particularly,
Matsen-Schick spectral analysis, hitherto applied only to rubberlike materials.


silicate melts;structure;entropy;unmixing

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X