1. Crystals and Their Structure

3. Unit Cells in the Cubic Crystal System

4. Simple Cubic

5. Body - Centered Cubic

6. Face - Centered Cubic

7. Cubic Closest Packing of Frozen Argon

8. Cubic Closest Packing of Frozen Methane

11. Coordination Number

12. Counting Cell Occupancy

13. Volume of the Unit Cell r is the radius of an atom in the unit cell r The volume of the unit cell is L 3 L But how do you get L? The Pythagorean Theorem, of course!

14. Volume of the Unit Cell L L r r r r

15. Calculating Packing Efficiency L L Packing efficiency is the ratio of the space occupied in the unit cell to the volume of the unit cell Cell occupancy = 4 r r r r

16. Sodium Chloride

18. Crystalline and Amorphous Silicon Dioxide Cristobalite, one of the crystalline forms of silicon dioxide, shows cubic closest packing. A glass made from silicon dioxide shows the amorphous disoriented structure.

19. STM of Silicon

20. STM of Gold www.ieap.uni-kiel.de/surface/ag-berndt/ mikro/images/stm.gif 3/27/02

21. STM Images www.almaden.ibm.com/vis/stm/atomo.html 3/27/02 Xe atoms on Ni substrate

22. STM Images www.almaden.ibm.com/vis/stm/atomo.html 3/27/02 Carbon monoxide on Pt

23. STM Images www.almaden.ibm.com/vis/stm/atomo.html 3/27/02 Fe corral on Cu substrate