Dear all, Hello! I am kinda confused and am thinking about the definition of twinning and disorder. I am just a starting student and might make some fundamental mistakes.
1) Twinning is a macroscopic phenomenon and the result is the addition of the intensity from different lattices; disorder is a microscopic phenomenon and the result is the addition of structure factors from different crystal "domains". Is this statement valid? 2) I am now very confused about how to define the macroscopic versus the microscopic level when I think of the systematic absences introduced by translational operation. Or in other words, can the translational operation between the twin domains create systematic absences? My answer is probably no because the distance between the two domains are too far away compared to the coherent length of the X-ray, i.e. the addition of the intensity alone cannot make some spots disappear. Is it true? If yes, what is the x-ray coherence length at the synchrotron in general? 3) If the statement in 2) is valid, then if a "twinning operation" can introduce systematic absences, this should be a disorder instead of a twin based on the definitions in 1). Is this right? Your answers will be greatly appreciated! Sincerely, Chen
