0.7 Solid state and superconductors  (Page 5/9)

The TAs will deduct points from your lab grade if the kits are not returned with all pieces present and properly organized.

Use of the solid state model kit:

The following instructions are abbreviated. Please consult the instruction manual found in the kits for more details if you need assistance in building any of the structures given. Note that some of the model kits are older than others and the manuals’and page numbers may not correspond.

There are four major part types in each model kit:

*2 off-white, thick plastic template bases with holes (one with a circle, the other a semicircle);

*cardboard templates (about 20 labeled A-T);

*metal rods (to be inserted in the holes to support the plastic spheres)

 *plastic spheres in 4 sizes and colors.

The spheres can represent atoms, ions, or even molecules depending upon the kind of solid it is.

You will be given directions for the use of a specific base, template, placement of the rods, selection of spheres, and arrangement of the spheres as you progress. The ICE model kits make use of Z-diagrams to represent how the structure will be built up. Each type of sphere will be numbered with the z layer in which it belongs.

As we build each structure in three-dimensional space, we will be drawing figures to represent the unit cell structures. Each level or layer of atoms, ions, or molecules in a unit cell can be represented by a two-dimensional base, that is, a square, hexagon, parallelogram, etc.

To draw the Z-diagrams the bottom layer is referred to as z=0. We then proceed layer by layer up the unit cell until we reach a layer which is identical to the z=0 layer. This is z=1. Since z=0 and z=1 are identical by definition, we do not have to draw z=1, although you might want to do so as you are learning how to work with solid state figures. The layers between top and bottom are given z designations according to their positions in the crystal. So, for example, a unit cell with 4 layers (including z=0 and z=1) would also have z=0.33 (1/3) and z=0.67 (2/3).

Each solid-state kit has two types of bases (one using rectangular coordinates, the other using polar coordinates) indicated by a full circle or semicircle, or by color (yellow and green.)

You will first build structures that involve only one type of atom, as you would find in crystalline solids of the elements, especially that of the metals. Then you will examine ionic compounds which are known as binary solids. Binary solids are those composed of only two types of atoms, such as sodium chloride or calcium fluoride.

If time permits there is an extra credit exercise you can do. You may not do this extra credit exercise until the report form has been completed nor may you receive credit for the extra credit assignment unless you fully complete the report form.

Working groups and teams

You and your lab partner will constitute a group. Each group will receive one model kit and two groups will work together as a team. Your TA will assign you the structures you have to do, and at the end each team will discuss the structures assigned on front of the class. The number of teams and the assignments the TA will give you will be decided based on the number of students in a particular laboratory session. The laboratory is divided for six teams (A-F)