Structure of Crystals

Question 1

Smallest Structure

Answer 1

unit cell

Question 2

Most common types of unit cells

Answer 2

Face-centered cubic, body-centered cubic, hexagonal close-packed

Question 3

n

Answer 3

number of atoms per unit cell

Question 4

m

Answer 4

adjacent unit cell number

Question 5

APF

Answer 5

atomic packing factor//fraction of volume of cell occupied by hard spheres//sum of atomic volumes/volume of cell

Question 6

Number of atoms per unit cell:

SC,BC,FC

Answer 6

SC: 1, BCC: 2, FCC: 4

Question 7

Coordination Number:

SC, BCC, FCC

Answer 7

SC: 6, BCC: 8, FCC: 12

Question 8

Single Crystals

Answer 8

whole solid is crystal

Question 9

Polycrystalline Materials

Answer 9

many crystalline grains, not aligned, where meet is called grain boundary

Question 10

Anistrophy

Answer 10

Different packing in different directions, deformation depends on direction stress is applied

Question 11

Non-crystalline

Answer 11

amorphous, no long range order

Question 12

Vacancy diffusion

Answer 12

movement to open space

Question 13

Interstitial diffusion

Answer 13

movement between smaller spaces

Question 14

homogenous material

Answer 14

random, routine movement, equal number of atoms in all directions

Question 15

inhomogenous

Answer 15

moving near randomly, migration of atoms to lower concentration, can become homogenous by diffusion

Question 16

Diffusion

Answer 16

homogenous, equal movement

Question 17

Net Diffusion

Answer 17

inhomogenous, higher concentrations

Question 18

Factors that influence diffusion

Answer 18

Barrier, size, direction, temperature, pathway (easier on surfaces or voids)