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Re: Re: aniso scaling
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Hello..
Continuing the argument on 'aniso' scaling..
>"Felix Vajdos" <vajdos@dna-mail4.gene.com> wrote:
>
>I don't have a good explanation for it, but my gut instinct tells
>me that it has to do with the fact that Xplor scales Fobs, not Fcalc.
>I can't really get my brain arond what may mathematically happening,...
>
Well, if you look into the text books on crystallography, the
simple equation for R-factor calculation involves a 'scale factor' (k)
which is 'always' applied to Fcalc.
like.. R-factor = Sigma(hkl)(w(|Fobs| - k|Fcalc|)/Sigma(hkl)|Fobs|
^
|-> scale factor
Even, if you look into the XTALMACRO of the X-PLOR module..
you will find the following lines..
macro {scalef}
(
.....
....
#f=fcalc; {name of structure factor array -- scaling will be applied }
....
....
#fref=fobs; {name of reference structure factor array (f will be scaled to
fref}
....
)
So, here, Fcalc is scaled to Fobs...
If I am wrong in pointing out this.... I 'm sorry.
Sincerely,
Ravi.
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______________________________________________________
| S.Ravichandran |
| Senior Research Fellow -2 |
| Crystallography & Molecular Biology Division |
| Saha Institute of Nuclear Physics |
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