The Structure of Crystals and Crystal Surfaces

In the nanoworld most things happen either at or near surfaces. The properties of the surfaces of crystalline materials are strongly dependent on the arrangement of atoms on the surface which is a truncation of the bulk crystalline lattice. (Actually sometimes surface reconstructs, but we will get to that in due time.). In order to intelligently discuss this topic we must first understand the basics of the crystallography. A very useful concept that we need to master is the Miller index, which is a way to describe crystal planes and directions.

We will make use of a number of very good resources on the WWW for our study of crystals and crystal surfaces. In NanoLab we will be largely concerned with the two close-paced crystal structures: face centered cubic (FCC) and hexagonal close packed (HCP) structures.

Reading assignment is part 1 of An Introduction to Surface Chemistry and three parts of CEM 924 Introduction to Surface Analysis: Drawings of Common Crystal Structures, Drawings of Some Low Index Crystal Planes, and Low Index Surfaces.

The study guide for this unit is here: <SG for Crystals & Surfaces>.

For the lab activity you will work in groups and explore crystal structures through our hands-on models. The Crystal Model Lab (pdf). An example of how to makes sketches of the exposed crystal faces of your stacks is shown here <sketch example>.

There are many excellent resources for crystallography on the WWW.

JCrystal is a nice software resource for visualizing crystal morphology. It is installed on the computers in the classroom. A number of sites have JCrystal-based Java applets. The Cubic-Hexoctahedral Crystal applet is particulary useful for us.

Structures of Simple Inorganic Solids from Dr. S.J. Heyes Inorganic Chemistry Course (4 lectures). The discussion of close packing of spheres is particulary relevent to us.

Check out the pictures in the Minerology Database they even have rotating crystals with Miller-index-labeled facets (and in stereo).