Hello everybody,
I have a question concerning the errors calculated in a rietveld
refinement. As far as I understand, the error of a parameter is calculated
as
sigma(p_i) = sqrt(c_ii) * sqrt(chi^2/N-P) (*)
where c_ii is the i-th diagonal element of the inverse of the
curvature matrix, chi^2 = sum_i w_i*(yobs_i - ycalc_i), N number of
observations, P number of parameters.
But I thought the statistical error is just sqrt(c_ii)! The second factor
is alway << 1, because N is a large number, and so the calculated errors
are much to small! Even more, I can minimize them by increasing the number
of steps, although, after a certain point, I gain no more information.
Any hints?
Thanks,
Michael
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| Dipl.-Min. Michael Chall |
| Kristallographie |
| Institut fuer Geowissenschaften |
| Universitaet Kiel |
| Olshausenstr 40 fon : +49 431 880 2692 |
| fax : 4457 |
| D 24098 Kiel mail: [EMAIL PROTECTED] |
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