Basic questions
 What is the general condition that particles/radiation can be used in diffraction?
(wavelength ~1Å or smaller than lattice parameter: d= 2-3 Å)

Why does the Debye-Scherrer method give only diffraction rings and how do these reflect the reciprocal lattice?
The xrays are diffraction with same angle 𝜽 in different directions forming a cone
Each set of planes for a given specific (hkl) value give rise to such a cone

What is the Debye-Waller factor?
Temperature dependance of diffraction spots
Perfect lattice only @ 0K, with increasing T° (thermal lattice vibration/ atom displacement: µ)
Mean displacement of atoms increase, 𝐷(𝑇) = 𝑒 (

⟨
⟩
)
0, intensity 0 (invisible spots)
Can you explain why high order diffraction spots, i.e. with large (h,k,l) give weaker diffraction spots
than low-indexes reflexes?
Effect of displacement becomes bigger with further atoms
Larger → less probable for diffraction
High index spot die out

What is the form factor? Can you explain the associated mathematical relation:
Shkl = fa∙exp(iGhkl∙ri)?
F: Contains information on basis and on nature of atoms
Determines the intensity of diffracted spots
Diffraction due to basis of unit cell
Inner atoms contribution/ effect on diffraction
 nbr of atoms in basis
fa atomic scattering factor: depends on the number of electrons in the atom.
exp(iGhkl∙ri) interference effect

Why can the form factor not produce diffraction spots
(no periodicity, symmetry, information on lattice periodicity)

What physical quantity is responsible for the atomic scattering yield fa?
(electron number, good scatterers are heavy elements: Au and bad scatterers are light elements: H)