Hi Shay
>From Bragg's equation we have:
delta_theta = (delta_d/d) Tan(Th)
Or, the amount a peak shifts is increases with 2Th but decreases with
d-spacing.
So at a d-spacing of 2 Angstroms say (200 pm) for a peak at 20 degrees 2Th
say we would see a shift in 2Th of:
(0.1 / 200) Tan(10 Pi/180) 360/Pi
= 0.0101 degrees 2Th
This is measureable - if my quick calculation is correct that is
Cheers
Alan
From: [email protected] [mailto:[email protected]] On Behalf
Of Shay Tirosh
Sent: Wednesday, 8 January 2014 12:23 AM
To: [email protected]
Subject: Very small shift in d-space: insanity check
Dear rietvelders
I would like to consult with you as for the possibility to determine small
shift in d-space in the order of 0.1pm in normal Bruker x-ray diffractometer
with
<https://www.google.co.il/search?q=bragg+brentano+geometry&biw=1280&bih=698&;
tbm=isch&tbo=u&source=univ&sa=X&ei=vwnMUo-BCo2IyQPlp4GgBg&sqi=2&ved=0CCoQsAQ
> Bragg Brentano geometry.
.
Detector:
Our diffractometer equipped with multi-channel Laynex detector. I used
solar slit and 0.6mm advancing slit.
Source:
Cu Kalpha1, Kalpha2.
Experiment:
Step size 0.02o
Time per each step 0.3sec
I used internal standard that has reflection peak at 2teta = 12.71o
I repeat the diffraction experiments 3 times.
Care has been taken not to move the sample between diffraction experiments.
Analysis:
All three diffraction experiments merged, baseline has been subtracted from
the merged data set. Position of the peak has been determined by fitting to
the best peak equation using Fityk. Shift in d-space has been determine with
respect to the internal standard peak reflection.
Parallel reflections gave similar shifts in the order of 0.1pm with relative
standard deviation of 8.65%.
Dose my result make sense?
Do I violate the limit of resolution?
Please comment.
Thank you from advance
Shay
--
_________________________________________________
Dr. Shay Tirosh
Institute for Nanotechnology & Advanced Materials
Bar Ilan University
Ramat Gan, 52900
Israel
Phone: +972-(0)30-531-7320
Mobile: +972-(0)54-8834533
Email: [email protected]
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