Thanks for making the video, really useful! Is there a name for the equation you started with, giving an expression for the amplitude of a diffracted beam? Or anywhere I can find more about it?
Dear Prof. Xie, thank you for these great videos. Could you tell me why the center beam always be (000)? And I am also not fully understand the 'two beam' condition. As you taught in Lecture 13.1, two beams actually refer the direct beam and the diffracted beam. Is the electron beam generated by electron gun same thing as the direct beam? And can I thins of the direct beam as (000) plane? Thank you very much.
Good question. I think the direct beam is marked as 000 more as a tradition. All planes are reciprocal. So 000 basically means infinity in all three dimensions. Just my speculation.
FCC and BCC have slightly different symmetry. In both TEM and XRD, you can do it by looking for forbidden reflections. For example, 110 is present in BCC but not in FCC; 111 is present in FCC but not in BCC. If you have bulk samples, XRD is the quickest way by comparing it to the standards in the database. Hope it helps.
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Great explanation, very good indeed.
Very clear explanation! Thank you sir
讲得很好，谢谢
Thanks for making the video, really useful! Is there a name for the equation you started with, giving an expression for the amplitude of a diffracted beam? Or anywhere I can find more about it?
Dear Prof. Xie, thank you for these great videos. Could you tell me why the center beam always be (000)? And I am also not fully understand the 'two beam' condition. As you taught in Lecture 13.1, two beams actually refer the direct beam and the diffracted beam. Is the electron beam generated by electron gun same thing as the direct beam? And can I thins of the direct beam as (000) plane?
Thank you very much.
Good question. I think the direct beam is marked as 000 more as a tradition. All planes are reciprocal. So 000 basically means infinity in all three dimensions. Just my speculation.
How do we know if a material is bcc, FCC or sc
FCC and BCC have slightly different symmetry. In both TEM and XRD, you can do it by looking for forbidden reflections. For example, 110 is present in BCC but not in FCC; 111 is present in FCC but not in BCC. If you have bulk samples, XRD is the quickest way by comparing it to the standards in the database. Hope it helps.
Thank you!