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This exercises uses beads to help show how different crystal structures are formed. The exercise includes 3D-printed boxes with starting structures incorporated in the bottom to increase the stability of structures that students build. The exercise also includes a number of additional 3D-printed manipulatives to help students visualize the unit cells and other properties of different crystal structures. These include unit cells with accurate atomic and hold dimensions and several different ways to visualize the layer structures in close-packed structures.
The goal is for students to learn how different crystal structures are formed from the packing of hard spheres.
Students will also learn how the different structures generate holes of different sizes and the different coordination numbers for the holes.
In addition to the 3D printed manipulatives included above, you will need tweezers or spatulas to manipulate the beads, and a variety of beads or other spherical objects. The exercise is written assuming that the structures are made of 8 mm beads, but the prints could be scaled for any size of sphere. Each group would need (approximately):
2 3 mm
2 4 mm
2 5 mm
2 6 mm
135 8 mm
16 8 mm Colored
1 10 mm
1 12 mm
1 14 mm
1 16 mm
1 1/2”
1 5/8”
1 3/4”
2 1”