Solids Flashcards
Features of covalent bonds
Strong
Highly directional
Features of ionic bonds
Strong
Purely coulombic
Between permanently charged atoms
Features of van der waals bonds
Between atoms with no net charge
Weak
Finding min separation
Differentiate van.d.waals potential
Cohesive energy and elements
Energy required to separate a crystal
- Ionisation energy
- Electron affinity
- Coulomb interaction
lattice
array of discrete points, same from every angle
Primative lattice vectors
any vector joining two points on a lattice
Unit cell
building block of the crystal
encloses minimum lattice points
Basis
arrangement of atoms at the lattice points
Arrangement of hexagonal close packing and coordination number
b on a on b - 12
Arrangement of face centered cubic packing and coordination number
b on a on c - 12
Definition of packing fraction
ratio of volume of spheres to volume of cube
limiting distance for FCC
face diagonal
limiting distance for BCC
body diagonal
requirement for diffraction
wavelength similar to spacing
Finding miller indices
- Find intercepts
- Reciprocate them
- Clear reciprocal of fraction
Definition of reciprocal lattice
set of imaginary points perpendicular to real space planes
Relationship between spacing and reciprocal length
inversely proportional
Advantages of x-rays
easily available
high penetrating power
similar wavelength
Disadvantages of x-rays
can destroy fragile samples
restrictive single wavelength
Advantages of neutrons
higher sensitivity to light
strong magnetic interactions
low energies
Disadvantages of neutrons
expensive
dim sources
resolution is poor
Types of defects
Grain boundaries
Dislocations
point defects
Dealing with polyatomic lattice vibrations
as a coupled oscillator
