1. hole Answer the following questions for both packing diagrams. 1.Draw the unit cell for each packing example. How many atoms I are there in each unit cell? 2.Accurately draw boxes exactly 3 atoms wide. How many total atoms are in each? Which displays the greater packing density ? Packing Efficiency of Unit Cells - 2D Example

2. Top Side views 2r r SIMPLE CUBIC PACKING 2r Packing Efficiency of Unit Cells Assume atoms hard spheres

3. 4r a a FACE CENTERED CUBIC - FCC 6 6 1 2 3 4 5 7 8

4. x 2 = a 2 + a 2 x = √2 a a 4r √2 a unit cell a a FACE CENTERED CUBIC - FCC Unit CellPack EffCoord # scp0.526 bcc0.688 fcc0.7412

5. unit cell: simple cubic AA How many red spheres touch yellow in first layer A? How many red spheres touch yellow in first layer A if there is an identical layer A in front of and behind the first A? What is the coordination number for scp?

6. BODY CENTERED CUBIC PACKING - ABAB A B How many spheres touch yellow in layer B? How many spheres touch yellow in layer B if a red layer A is added below and above B? What is the coordination number for bcc?

7. A CUBIC CLOSEST PACKING How many spheres touch yellow in layer A? How many spheres touch yellow in layer B? How many spheres touch yellow in layer C? What is the coordination number for FCC (or hcp)?

8. Unit CellPacking EffCoord # Simple Cubic0.526 Body centered0.688 Face centered0.7412