structure of metals (part 2) Atomic packing factor

Question 1

What does apf stand for

Answer 1

Atomic packing factor

Question 2

simple cubic what is a / r

Answer 2

a = 2R or R=0.5a

Question 3

what is Vc

Answer 3

Volume of unit cell

Question 4

What is Vs

Answer 4

Volume of atoms in a unit cell

Question 5

what is the formula of Vc

Answer 5

Vc= a^3

Question 6

what is the formula Vs

Answer 6

Vs=n x 4/3 pi R^3

Question 7

what is the Vc for a simple cubic?

Answer 7

Vc= (2R)^3

Vc=8r^3

Question 8

what is n for a simple cubic

Answer 8

n =(1/8*8) = 1 atoms due to all the atoms being on the edges

Question 9

Vs simple cubic

Answer 9

Vs= 1*4/3piR^3
=4/3pi R^3

Question 10

what is the APF of a simple cubic

Answer 10

0.52

Question 11

Some characteristics of Sc

Answer 11

-they are rare due to low packing density
-closed-packed directions are cube edges

Question 12

coordination number of SC

Answer 12

6

Question 13

Give an example of an element that has Sc

Answer 13

Po (polonium)

Question 14

How to find the a for a BCC

Answer 14

using Pythagoras
(a(root2))^2 + a^2 = (4R)^2
a=4/(root3) R

Question 15

what is n for BCC

Answer 15

n= 2
because (1/8*8)+1

Question 16

APF of BCC is

Answer 16

0.68

Question 17

why is BCC APF smaller the FCC

Answer 17

due to BCC having less neighing atoms then FCC its APF is less the FCCs’

Question 18

coordinate number of BCC

Answer 18

8

Question 19

Example of BCC elements

Answer 19

chromium Cr, W tungsten, Fe(Iron),tantalum, Molybdenum.

Question 20

What is the a of an FCC

Answer 20

using pythagros theorm:
a^2 + a^2 = 4R
a= s(root2)R

Question 21

what is the n of an FCC

Answer 21

n = 4
(1/88) + (1/26)

Question 22

what is the FCC of APF

Answer 22

0.74

Question 23

co ordination number of FCC

Answer 23

12

Question 24

feature of an FCC

Answer 24

-atoms are located at each of the corners and on the centers of all the faces of a cubic unit cell
- atoms touch each other along face diagonals

Question 25

examples of FCC

Answer 25

Al, Cu, Gold silver, lead, nickel and platinum

Question 26

what is the maximum APF

Answer 26

0.74

Question 27

what is the is structure of HCP

Answer 27

ABAB and 3D projection

Question 28

what is the coordination of HCP is

Answer 28

12

Question 29

c/a is hcp

Answer 29

1.633

Question 30

how many atoms in the unit cell

Answer 30

6 atoms

Question 31

example

Answer 31

magnism and Ti, Zinc, Cd