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Crystals and Their Structure. Unit Cells in the Cubic Crystal System.

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Presentation on theme: "Crystals and Their Structure. Unit Cells in the Cubic Crystal System."— Presentation transcript:

1 Crystals and Their Structure

2

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

9

10

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

17

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 mikro/images/stm.gif 3/27/02

21 STM Images 3/27/02 Xe atoms on Ni substrate

22 STM Images 3/27/02 Carbon monoxide on Pt

23 STM Images 3/27/02 Fe corral on Cu substrate


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