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GEOREF RECORD

Role of internal pressure in a ferroelastic phase transition

Nikolay N. Ovsyuk and Sergei V. Goryainov
Role of internal pressure in a ferroelastic phase transition (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): 215-222

Abstract

It is shown that softening the acoustic mode, which brings about the occurrence of a proper ferroelastic phase transition in some crystals, is substantially due to the "kinematic" anharmonicity. The latter arises at the transition from the natural curvilinear coordinates of interatomic separation to the Cartesian atomic displacements. It is shown that the internal pressure may be represented as driving force for a proper ferroelastic phase transition induced by cation exchange. It has been found that the internal stress tensor, generated by the cation exchange, is of a more complicated nature than the tensor of the external stress. This difference comes from a specific coupling of the substituting cations with local, microscopic displacements of the neighbouring atoms inside the unit cell. It becomes evident why in a number of experiments a significant difference in the action of internal and external pressures on the crystal structure is observed and, also, why the internal pressure causes the greater anisotropy than the external one. We have obtained an equation for the crystals, in which the softening of the acoustic modes is caused only by the kinematic anharmonicity, with whose help we can predict either the external pressure of the ferroelastic phase transition to a triclinic phase if the initial elastic moduli are known or the internal pressure induced by cation exchange for the isotropic case.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 17
Serial Issue: 2
Title: Role of internal pressure in a ferroelastic phase transition
Title: EMPG X; Experimental mineralogy, petrology and geochemistry
Author(s): Ovsyuk, Nikolay N.Goryainov, Sergei V.
Author(s): Woodland, A. B.editor
Author(s): Foley, S. F.editor
Affiliation: Russian Academy of Sciences, Institute of Mineralogy and Petrology, Novosibirsk, Russian Federation
Pages: 215-222
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: 34
Accession Number: 2005-041695
Categories: Mineralogy of silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200525
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