Chong Solid State

Question 1

What is a crystal

Answer 1

A regular, periodic rearrangement of atoms, ions or molecules

Question 2

What is a unit cell

Answer 2

A repeating unit that can generate the entire crystal by translation in three dimensions

Question 3

What is a lattices periodicity?

Answer 3

The regular and repeating pattern within the atoms that make up the solid

Question 4

What is the lattice of a structure

Answer 4

The symmetrical 3d arrangement of atoms inside a crystal

Question 5

What is a motif ?

Answer 5

A set of atoms arranged in a particular way

Question 6

What is the crystal structure a combination of ?

Answer 6

The lattice and the motif

Question 7

What is a primitive unit cell

Answer 7

-smallest unit cell by volume
-only one lattice point
- not unique

Question 8

What is the relationship between the sides and angles in a cubic unit cell

Answer 8

Sides a=b=c
Angles alpha = beta = gamma

Question 9

What are miller indices

Answer 9

Used to describe planes and directions with respect to the crystal lattice
Consists of a set of three integers, hkl

Question 10

What stacking sequence does Cubic close packing have ?

Answer 10

ABCABC

Question 11

How many atoms are in the unit cell of a ccp

Answer 11

4

Question 12

How do you calculate the packing efficiency?

Answer 12

PE = n(atoms in unit cell) x V(atom) / V( unit cell)

Question 13

What is the stacking sequence for hexagonal close packing

Answer 13

ABABAB

Question 14

What is the packing efficiency and CN of a simple cubic packed crystal

Answer 14

PE= 0.52
CN= 6

Question 15

What is the packing efficiency and CN of a body centred cubic crystal

Answer 15

PE= 0.68
CN= 8

Question 16

What is the packing efficiency and CN of a cubic close packed crystal

Answer 16

PE= 0.74
CN= 12

Question 17

What is the packing efficiency of a hexagonal close packed crystal

Answer 17

PE= 0.74
CN= 12

Question 18

What is an alloy

Answer 18

Metallic solid which contains atoms of more than one element

Question 19

What are the types of alloys

Answer 19

Substitutional and interstitial

Question 20

What is a substitutional alloy

Answer 20

An exchange of atoms of one element for another

Question 21

What is an interstitial alloy

Answer 21

Additional atoms of another element sit between atoms of host lattice

Question 22

What is an ionic solid

Answer 22

A solid that consists of positively and negatively charged ions ( anions and cations )

Question 23

What forces are ideal ionic solids held together by

Answer 23

Electrostatic forces

Question 24

How is the arrangement of an ionic solids held together stabilised

Answer 24

Maximising anion- cation interactions and minimising anion- anion interactions

Question 25

How can many ionic solids be described in terms of arrangement

Answer 25

Close packed arrangements of ions with oppositely charged ions occupying interstitial sites

Question 26

What are the two types of interstitial sites

Answer 26

Tetrahedral holes and octahedral holes

Question 27

What is the radius ratio rule

Answer 27

.y=r(small ion)/ r(large ion)

Question 28

What are some limitations of the radius ratio rule

Answer 28

Ions are assumed to be perfect spheres Doesn’t account for attractive or repulsive forces , orbital overlap and covalency

Question 29

If a structure has radius ratio of 1-0.732 what CN does it have and in which interstitial site are the oppositely charged ions occupying

Answer 29

CN is 8 Occupying the cubic interstitial sites

Question 30

If a structure has radius ratio 0.732-0.414 what CN does it have and which interstate sites are the oppositely charged ions occupying

Answer 30

CN is 6 Occupying octahedral interstitial sites

Question 31

If a structure has radius ratio 0.414-0.225 what is its CN and which interstitial sites are the oppositely charged ions occupying

Answer 31

CN is 4 Occupying the tetrahedral interstitial sites

Question 32

If a structure has radius ratio of 0.225-0.155 what is its CN and which interstitial sites does the oppositely charged ions occupy

Answer 32

CN os 3 Occupying the trigonometric interstitial sites