Interactive Tutorial about Diffraction
Interactive example: Solutions

Diffuse scattering
Thermal I
Thermal II
Occupational I
Occupational II
Longitudinal waves
Transversal waves
Short range order
Stacking faults

Interactive examples
Displacement waves
Short range order
Stacking faults


  • Example 1: The propagation direction determines the directions in which the satellites are observed, the wavelength determines the distance from the Bragg reflections. The oscillation direction on the other hand determines the direction of the intensity modulation of the Bragg and satellite peaks. The phase has no influence on the observed intensities. Be careful when changing the wavelength. If it gets too short with respect to the lattice parameter (5A), the wave has no sinusoidal character any more and one can e.g. observe different satellite intensities at +-k around the Bragg peak !

  • Example 2: The patterns can be generated using the correlations (i) all 0.0, (ii) a100 positive, rest 0 for chains of a200 negative for pairs, (iii) a100,a010 negative and a110,a1-10 positive and (iv) all positive. A positive correlation a100 for example creates diffuse streaks through the Bragg peaks parallel to k and a negative a100 will give the same streak between Bragg peaks. One can think of this as a local doubling of the unit cell creating 'new' Bragg peaks at half positions. For more details review the analytical expression given in the SRO section of the tutorial. It should also be noted that the scattering intensity is symmetric around the Bragg positions. Finally the extend of the short range order and the width of the diffuse features are reciprocal to each other, sharp features in reciprocal space correspond to 'longer range' disorder and vice versa.
© Th. Proffen and R.B. Neder, 2003