Presentation on theme: "Øystein Prytz Introduction to diffraction 2 Øystein Prytz."— Presentation transcript:
Øystein Prytz Introduction to diffraction 2 Øystein Prytz
Summary from last time θ Vector normal to a plane
Øystein Prytz The structure factor B A Origin Incoming wave: Wave scattered from atom A: Equivalent expression for atom B Total scattered wave detected far away: Can be calculated for all scattering vectors (angles) Δk, but usually we only concern ourselves with Δk=g (destructive interference in all other cases)
Øystein Prytz The structure factor for copper fcc lattice with one atom in  relative to the lattice point. r 1 = [0,0,0], r 2 = [1/2,1/2,0], r 3 = [1/2,0,1/2], r 4 = [0,1/2,1/2]
Øystein Prytz The structure factor for copper Result: hkl even: F=f Cu (1+1+1+1)=4f Cu hkl odd: F=f Cu (1+1+1+1)=4f Cu h odd, k and l even: F=f Cu (1-1+1-1)=0 h and k odd, l even: F=f Cu (1+1-1-1)=0 Conclusion: hkl even or odd gives allowed reflections, hkl mixed gives forbidden reflections
Øystein Prytz The reciprocal lattice for bcc iron? Body centered cubic lattice One atom per lattice point,  relative to the lattice point What is the reciprocal lattice?