Integrating Research and Education > Crystallography > Order/Disorder Within Crystal Structures as a Function of Temperature

Order/Disorder Within Crystal Structures as a Function of Temperature

Kent Ratajeski
Department of Earth Sciences, Montana State University, Bozeman, MT
Published Jan. 25, 2005

Description

The olivine unit cell. Crystallographic sites house Si (black), O (red), and the M1 (brown) and M2 (orange) cations (Mg and Fe). Details

This exercise is based on recent crystallographic research on the olivine crystal structure published by Redfern et al. (2000). The authors of this study synthesized Fa50 olivine olivine (MgFeSiO4) in an experimental apparatus at temperatures ranging from 100 to 1250 °C, quenched the experiments, and used in situ neutron powder diffraction techniques to investigate changes in the synthesized olivines as a function of temperature. While this study reports cutting-edge materials research carried out with the latest crystallographic techniques, the results are educationally instructive and illustrate important concepts normally covered in an undergraduate mineralogy course.

In this exercise, students are guided into the American Mineralogist Crystal Structure Database to retrieve and download published crystal structure data for viewing in either the CrystalMaker or XtalDraw visualization software packages. The students are instructed on how to manipulate the structures and are asked to plot some of the crystallographic data from this study on graphs using a spreadsheet program such as Excel.

Reference

Redfern, S.A.T., Artioli, G., Rinaldi, R., Henderson, C.M.B., Knight, K.S., and Wood, B.J. (2000) Octahedral cation ordering in olivine at high temperature. II: an insitu neutron powder diffraction study on synthetic MgFeSiO4 (Fe50). The Physics and Chemistry of Minerals, 27, 630-637.


This exercise is one of several examples featured in the Teaching Mineralogy with Crystal Structure Databases and Visualization Software module at SERC. Each example is designed to give instructors and students direct practice for using crystal structure databases and visualization programs to teach crystallography and mineralogy in the earth sciences. Students should begin by Selecting Your Visualization Software.

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