About XRD's basic issues of single crystal and polycrystalline diffraction peaks

Your crystal test plane is 001, and the X -ray is reflected on the 001 surface or is called diffraction. Other planes will definitely not be measured.There are 45 degrees angle at two points.EssenceEssence

This problem is indeed very elementary, so you should make up for it.Powder diffraction is polycrystalline diffraction, which are available in all directions, so you can see the diffraction peaks of different crystal surfaces. The angle corresponds to different crystal spacing.Because the single crystal has only one direction, the face is the same, naturally there is only one peak, and the crystal surface distance of different orientation is different, so the peak positions are different.If you rotate a plane, the diffraction surface of the crystal has not changed, and the test results are natural. However, if you put the crystal oblique, the direction will be different, and the peak position will change.It's not easy to type mobile phones. Look at the book and understand how to analyze the principle.

A way of placement corresponds to one direction, single crystal can only see one peak.For the crystal of the cubic structure, it must be a single peak. For the non -cube structure, the crystal cells are often fell down in the crystal growth, so the 001 direction is equivalent to 100,010.3 peaks, but the angle is closer.

In recent years, the X -ray diffraction instrument has been bought in general schools. In other words, almost all school students can do XRDs, only to queue up. At the same time, the form of the Prague equation is too simple. There is a high school geometric knowledge basis. You can understand this equation at a glance, and the form of the XRD diagram only includes peak heights and angles. This has caused a large number of XRD diagrams in academic papers to play a role in academic research. use. Let me answer these questions.
1 Be sure to understand the concept of the diffraction vector, which refers to the direction of the law line of the crystal surface;
2 During the conventional powder diffraction process, the direction of the diffraction vector will never change;
3 in the conventional conventional During the powder diffraction process, with the changes of the THETA angle, any HKL crystal surface will appear in the direction of the diffraction vector (this is because the orientation of the powder grain is random), so as long as the spacing of a certain HKL crystal surface D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D d D. Value meets the Prague equation, then the diffraction peak will appear. Note that the Prague equations are not sufficient conditions.
4 above, if you can understand, please think about the problems I have given you. The Prague equation can be written in two forms, one is 2dsin (theta) u003d n, and the other is 2dsin (theta (theta ) u003d Try, please tell me, which equation covers the Miller index and which equation covers the broad -faire surface index in a broad sense?

Look at the information of the basic principles of powder diffraction, and you understand