Chapter 3 - Structure of Crystalline Solids

Question 1

What materials have crystalline structures?

Answer 1

All metals, most ceramics, some polymers

Question 2

What are noncrystalline materials called?

Answer 2

Amorphous

Question 3

When atoms are modeled as solid spheres, what is the model called?

Answer 3

Atomic Hard Sphere Model

Question 4

What is the smallest pattern observed in a crystal structure called?

Answer 4

Unit Cell

Question 5

How many total atoms does a FCC unit cell have?

Answer 5

4 atoms (1/2 atoms at each face, 1/8 atoms at each corner)

Question 6

What is the unit cell length of a FCC structure?

Answer 6

2Rsqrt(2)

Question 7

What is the Atomic Packing Factor of an BCC unit cell

Answer 7

0.68

Question 8

What is a coordination number?

Answer 8

The number of atoms an atom is bonded to

Question 9

What is the coordination number for a FCC unit cell

Answer 9

12

Question 10

How can you tell an atom has an FCC structure from its indices?

Answer 10

The indices are all odd, or all even

Question 11

How can you tell an atom has an FCC structure from the first 2 diffraction angles?

Answer 11

The ratio of the first 2 sin^2(theta) are 0.75

Question 12

Which crystal structure’s unit cell is composed of 2 whole atoms?

Answer 12

Body Centered Cubic

Question 13

What is the unit cell length of BCC structures?

Answer 13

4*R/sqrt(3)

Question 14

Which crystal structure(s) has an atomic packing factor of 0.74?

Answer 14

Both FCC and HCP

Question 15

Alpha, Gamma, and Delta irons, have what crystal structures?

Answer 15

Alpha and Delta have BCC, Gamma has FCC

Question 16

What is the coordination number for BCC structures?

Answer 16

8

Question 17

How can you tell if a structure is BCC based on its indices?

Answer 17

The sum of the indices is even

Question 18

Given the ratio of the first 2 sin^2(theta) is 0.5, what is the crystal structure?

Answer 18

BCC

Question 19

How many atoms does a HCP structure contain?

Answer 19

6 total atoms

Question 20

What is the ideal ratio of the lengths of the short and long sides (a and c respectively)

Answer 20

1.633

Question 21

What do you call a material that can have multiple crystal structures?

Answer 21

Polymorphism

Question 22

What is allotropy?

Answer 22

Polymorphism that occurs within an elemental solid

Question 23

What are the reflection indices for BCCs first 3 planes?

Answer 23

(110), (200), (211)

Question 24

Given the first 3 sums of the squared indices are 3, 4, 8, the crystal structure is what?

Answer 24

fCC

Question 25

Given the sum of the squared indices of the first 3 planes are 2, 4, 6, what is the crystal structure?

Answer 25

BCC

Question 26

What is the pattern of the planes of a simple cubic structure?

Answer 26

(x00), (x10), (x11) where x starts at 1 and increases every 3 planes

Question 27

What do the relative intensities given by x-ray diffraction imply within the unit cell?

Answer 27

The arrangements in atoms

Question 28

What does Bragg’s Law describe?

Answer 28

The relationship between wavelength, and angle of diffraction, and distance between atoms given planar indices and unit cell length.

Question 29

What is a single crystal?

Answer 29

A crystal with no grain boundaries

Question 30

What is isotropy?

Answer 30

When there is no directionality

Question 31

What is the pattern of stacked planes in FCC?

Answer 31

ABC pattern

Question 32

What is the pattern of stacked planes in BCC?

Answer 32

ABAB

Question 33

What is the pattern of stacked planes in HCP?

Answer 33

ABAB