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Fine
Post  Post subject: X ray diffraction spectrum analysis  |  Posted: Tue Dec 13, 2016 8:27 pm

Joined: Tue Dec 13, 2016 8:20 pm
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Hi. I'm studying x ray diffraction and found that most of the peaks in the spectrum have a of mirror symmetry even when they broaden, but sometimes that not the case. At first I thought that it was because of overlapping of peaks for two different places but found out that that's not the case. So why do some XRD peaks not show mirror symmetry when broadening? I know it must be something really simple that I'm missing and it erks me.
Thanks for your time and help.


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PhDemon
Post  Post subject: Re: X ray diffraction spectrum analysis  |  Posted: Tue Dec 13, 2016 9:03 pm

Joined: Wed Jun 26, 2013 10:44 am
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Location: Newcastle-upon-Tyne

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It's a long time (~20 years!) since I've had to bother with XRD but two possibilities off the top of my head are non-uniform diffracting domain size and dislocations (or concentration gradients) in the sample.


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Fine
Post  Post subject: Re: X ray diffraction spectrum analysis  |  Posted: Tue Dec 13, 2016 9:40 pm

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Would you please explain what diffraction domain size means?


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PhDemon
Post  Post subject: Re: X ray diffraction spectrum analysis  |  Posted: Tue Dec 13, 2016 9:59 pm

Joined: Wed Jun 26, 2013 10:44 am
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Location: Newcastle-upon-Tyne

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A scattering domain is a part if the sample that acts as a single crystal. In powder XRD you have millions of these randomly orientated in the sample. If they are not all of uniform size they may diffract X rays slightly differently leading to asymmetries in the peaks.


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