Chong Solid State Flashcards
What is a crystal
A regular, periodic rearrangement of atoms, ions or molecules
What is a unit cell
A repeating unit that can generate the entire crystal by translation in three dimensions
What is a lattices periodicity?
The regular and repeating pattern within the atoms that make up the solid
What is the lattice of a structure
The symmetrical 3d arrangement of atoms inside a crystal
What is a motif ?
A set of atoms arranged in a particular way
What is the crystal structure a combination of ?
The lattice and the motif
What is a primitive unit cell
-smallest unit cell by volume
-only one lattice point
- not unique
What is the relationship between the sides and angles in a cubic unit cell
Sides a=b=c
Angles alpha = beta = gamma
What are miller indices
Used to describe planes and directions with respect to the crystal lattice
Consists of a set of three integers, hkl
What stacking sequence does Cubic close packing have ?
ABCABC
How many atoms are in the unit cell of a ccp
4
How do you calculate the packing efficiency?
PE = n(atoms in unit cell) x V(atom) / V( unit cell)
What is the stacking sequence for hexagonal close packing
ABABAB
What is the packing efficiency and CN of a simple cubic packed crystal
PE= 0.52
CN= 6
What is the packing efficiency and CN of a body centred cubic crystal
PE= 0.68
CN= 8
What is the packing efficiency and CN of a cubic close packed crystal
PE= 0.74
CN= 12
What is the packing efficiency of a hexagonal close packed crystal
PE= 0.74
CN= 12
What is an alloy
Metallic solid which contains atoms of more than one element
What are the types of alloys
Substitutional and interstitial
What is a substitutional alloy
An exchange of atoms of one element for another
What is an interstitial alloy
Additional atoms of another element sit between atoms of host lattice
What is an ionic solid
A solid that consists of positively and negatively charged ions ( anions and cations )
What forces are ideal ionic solids held together by
Electrostatic forces
How is the arrangement of an ionic solids held together stabilised
Maximising anion- cation interactions and minimising anion- anion interactions
How can many ionic solids be described in terms of arrangement
Close packed arrangements of ions with oppositely charged ions occupying interstitial sites
What are the two types of interstitial sites
Tetrahedral holes and octahedral holes
What is the radius ratio rule
.y=r(small ion)/ r(large ion)
What are some limitations of the radius ratio rule
Ions are assumed to be perfect spheres
Doesn’t account for attractive or repulsive forces , orbital overlap and covalency
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
CN is 8
Occupying the cubic interstitial sites
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
CN is 6
Occupying octahedral interstitial sites
If a structure has radius ratio 0.414-0.225 what is its CN and which interstitial sites are the oppositely charged ions occupying
CN is 4
Occupying the tetrahedral interstitial sites
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
CN os 3
Occupying the trigonometric interstitial sites
