If you have a lattice spread equal to delta p (where p is one of the
lattice constants)
then the spread in theta will be via bragg's law:
delta theta
-------------- = C tan(theta)
delta p
(C is a constant that can be worked out for particular cases)
this means FWHM = sqrt[ (Uo + 2C delta p)tan2(theta) + ...]
I am sure there are more elegant ways of doing this as well.
(See Elcombe and Howard in Materials Science Forum Vol 27/28 (1988) p71-76
for more details)
Ciao
Brett
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Dr Brett Hunter
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ANSTO
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