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The free energy of formation of Mg (sub 2) TiO (sub 4) (synthetic qandilite), an inverse spinel with configurational entropy

Hugh S. C. O'Neill and Dean R. Scott
The free energy of formation of Mg (sub 2) TiO (sub 4) (synthetic qandilite), an inverse spinel with configurational entropy (in EMPG X; Experimental mineralogy, petrology and geochemistry, A. B. Woodland (editor) and S. F. Foley (editor))
European Journal of Mineralogy (April 2005) 17 (2): 315-323

Abstract

Syntheic qandilite is an inverse spinel in which random mixing of Mg and Ti on the octahedral site should give rise to a configurational entropy of 11.5 J K (super -1) mol (super -1) . The free energy of formation of Mg (sub 2) TiO (sub 4 ) has been determined from the location of the univariant reaction MgTiO (sub 3) + MgO = Mg (sub 2) TiO (sub 4) in P-T space between 0 and 20 kbar; together with published data for MgTiO (sub 3) and MgO, the results give S (super 0) (sub (298 K)) = 111.2 + or - 0.6 J K (super -1) mol (super -1) for Mg (sub 2) TiO (sub 4) . This entropy is only 7.6 + or - 0.9 J K (super -1) mol (super -1) more than the calorimetrically determined value of 103.6 + or - 0.7 J K (super -1) mol (super -1) . The discrepancy implies either considerable short-range order of Mg and Ti (super ) in Mg (sub 2) TiO (sub 4) , or perhaps an error in the high-temperature heat-capacity data for MgTiO (sub 3) caused by disordering.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 17
Serial Issue: 2
Title: The free energy of formation of Mg (sub 2) TiO (sub 4) (synthetic qandilite), an inverse spinel with configurational entropy
Title: EMPG X; Experimental mineralogy, petrology and geochemistry
Author(s): O'Neill, Hugh S. C.Scott, Dean R.
Author(s): Woodland, A. B.editor
Author(s): Foley, S. F.editor
Affiliation: Australian National University, Research School of Earth Sciences, Canberra, Australia
Pages: 315-323
Published: 200504
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
Meeting name: 10th international symposium on Experimental mineralogy, petrology and geochemistry
Meeting location: Frankfurt, DEU, Federal Republic of Germany
Meeting date: 20040404April 4-7, 2004
References: 21
Accession Number: 2005-041705
Categories: Mineralogy of non-silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200525
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