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From 2D to 3D: II. TEM and AFM Images

Peter Buseck
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Arizona State University
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Summary

High-resolution transmission electron microscopy (HRTEM) provides 2-D projections of mineral structures at almost the atomic scale, and atomic force microscopy (AFM) provides 3-D information about the surfaces of minerals. By using these instruments, we can learn about defects in minerals and their complexities. The mineral examples in this problem set include representatives from several silicate structure type, sulfides, a sulfosalt, and a carbonate.

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Context

Audience

This problem set is designed for a sophomore or junior level required course in mineralogy.

Skills and concepts that students must have mastered

Students should have a familiarity with plane groups and symmetry as well as a basic understanding of mineralogy and crystallography. Parts of the section on alkali feldspars require a basic familiarity with and knowledge of the reciprocal lattice and interpreting simple diffraction patterns.

How the activity is situated in the course

This is a stand-alone project that works well after completing the "From 2D to 3D: Escher drawings" exercise.

Goals

Content/concepts goals for this activity

The goals of this activity are to introduce students to the use of HRTEM and AFM to analyze crystal structure and symmetry. The exercise uses images to help students interpret the data from these instruments.

Higher order thinking skills goals for this activity

This activity involves analyzing data.

Other skills goals for this activity

The activity may involve writing skills and working in groups, depending on how you use it in your classroom.

Description of the activity/assignment

The problems in the accompanying exercises, "From 2D to 3D: Escher drawings", deal with abstractions that can be related to minerals through geometrical features they have in common. However, we are utimately interested in real minerals, their symmetries, and complexities.
High-resolution transmission electron microscopy (HRTEM) provides 2-D projections of mineral structures at almost the atomic scale, and atomic force microscopy (AFM) provides 3-D information about the surfaces of minerals. By using these instruments, we can learn about defects in minerals and their complexities. The mineral examples in this problem set include representatives from several silicate structure type, sulfides, a sulfosalt, and a carbonate. Interpretation of the images is less clear-cut than of the idealized drawings. In some cases the results can be ambiguous, but the provide a scope for fruitful discussions among class members.
In a few cases, references are given to the published papers from which the images are taken. These can be used to draw students into the professional literature, even though it will not always be possible to arrive at unambiguous answers. These problems should be thought provoking and yet manageable at several levels of complexity.

Determining whether students have met the goals

Students have met the goals of this activity if they answer the problem set questions thoroughly and accurately.

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