Fachbereich 14 - Geowissenschaften
Institut für Mineralogie
Allgemeine und Angewandte Mineralogie

Phase transformations in minerals

Phase transformations in minerals (including displacive transformations, order-disorder transformations, and exsolution), with particular reference to the evolution of the microstructure, as studied by transmission electron microscopy (incorporated in the Interdisciplinary Centre for Electron Microscopy and Microanalysis) as well as the characterization of structural changes by diffraction and spectroscopic methods. Structural changes as a function of temperature in ionic conductors are being studied as part of the Special Research Area (Sonderforschungsbereich SFB 458 : Ionenbewegung in Materialien mit ungeordneten Strukturen - vom Elementarschritt zum makroskopischen Transport). Computational methods and statistical thermodynamic modelling are being used to determine the thermodynamic properties of solid solutions with different degrees of short and long range order. Application of spin models and the calculation of phase diagrams in aluminosilicate systems is part of the special research area (Schwerpunkt Programme) "Structural Gradients in Crystals"

Drittmittelgeber:

Deutsche Forschungsgemeinschaft, Alexander-von-Humboldt-Stiftung, BMBF, Europäische Gemeinschaft, VGB Stiftung

Beteiligte Wissenschaftler:

Dr. U. Becker, Dr. Ute Golla-Schindler, Dr. R. Harrison, Dr. T. Kasama, Dr. Hinrich-Wilhelm Meyer, Dr. Liu Hong-Chao, Dr. Victor Vinograd, K. Pollok, Prof. Andrew Putnis

Veröffentlichungen:

Vinograd V.L. and Putnis A. A two-dimensional spin model of Al/Si order in feldspars: visualization of SRO and LRO. European Journal of Mineralogy. 13, 273-288 (2001)

Vinograd V., Putnis A and Kroll H. Structural discontinuities in plagioclase and constraints on mixing properties of the low series: a computational study. Mineralogical Magazine. 65, 1-31 (2001)

Golla U. and Putnis A. Valence state mapping and quantitative electron spectroscopic imaging of exsolution in titanohematite by energy filtered TEM. Physics and Chemistry of Minerals 28, 119-129 (2001)

Pollok K., Jamtveit B. and Putnis A. Analytical transmission electron microscopy of oscillatory zoned grandite garnets. Contributions to Mineralogy and Petrology 141, 358-366 (2001)

Harrison R.J. and Redfern S.A.T. Short- and long-range ordering in the ilmenite-hematite solid solution. Physics and Chemistry of Minerals 28, 399- 412 (2001)

Vinograd V. Configurational entropy of binary solid solutions. In: Solid Solutions in Silicate and Oxide Systems. Charles Geiger (Ed). EMU Notes in Mineralogy Vol 3 Chapter 12, 303-346 (2001)

Harrison R.J. and Becker U. Magnetic ordering in solid solutions. In: Solid Solutions in Silicate and Oxide Systems. Charles Geiger (Ed). EMU Notes in Mineralogy Vol 3 Chapter 13 349-383 (2001)

Liu Hong Chao, Harrison R. and Putnis A. A new triclinic phase of relaxor La-modified Pb(Zr0.65Ti0.35)O3 and its structure at 40K by high resolution neutron diffraction. J. Appl. Phys. 90, 6321 - 6327 (2001)

McEnroe S.A., Harrison R.J., Robinson P., Golla U. and Jercinovic M.J. Effect of fine-scale microstructures in titanohematite on the acquisition and stability of natural remanent magnetisation in granulite facies metamorphic rocks, southwest Sweden: Implications for crystal magnetism. Journ. Geophys. Res. 106, 30,523-30,546 (2001)

Becker U. and Pollok K. Molecular simulations of interfacial and thermodynamic mixing properties of the grossular-andradite garnets. Physics and Chemistry of Minerals, 29, 52-64 (2002)

Harrison R., Dunin-Borkowski, R.E. and Putnis A. Direct imaging of nanoscale magnetic interactions in minerals. Proc. Nat. Acad. Sci. 99, 16556-16561 (2002)

Golla-Schindler U., Benner G. and Putnis A. Laterally resolved EELS and ELNES mapping of the Fe L2,3- and O K-edge. Ultramicroscopy. (In press)

Vinograd V.L. Thermodynamics of mixing and ordering in the diopside-jadeite system: I. A CVM model. Mineralogical Magazine 66, 513-536 (2002)

Vinograd V.L. Thermodynamics of mixing and ordering in the diopside-jadeite system: II. A polynomial fit to the CVM results. Mineralogical Magazine 66, 537-545 (2002)

Kasama T., Golla-Schindler U. and Putnis A. High-resolution and energy-filtered TEM of the interface between hematite and ilmenite exsolution lamellae: Relevance to the origin of lamellar magnetism American Mineralogist. (In press)