Hi Bernhard
I'm sure you're right: it must be a typo. I think the problem is that
people get into the habit of including the minus sign in
EXP(-B*2*SINTH**2/L**2), e.g. when writing the expression for structure
factor, without thinking whether the formula is actually applicable to
the particular situation!
Cheers
-- Ian
> -----Original Message-----
> From: [log in to unmask]
> [mailto:[log in to unmask]] On Behalf Of Bernhard Rupp
> Sent: 24 April 2007 01:20
> To: [log in to unmask]
> Subject: truncate Wilson printout
>
> Dear All,
>
> there is one line in the TRUNCATE output that makes
> me question my sanity.
>
> Under the Wilson plot the log states:
>
> Least squares straight line gives: B = 12.743 SCALE
> = 22.25070
> where F(absolute)**2 = SCALE*F(observed)**2*EXP(-B*2*SINTH**2/L**2)
>
> This is somewhat counterintuitive, because in order to get the
> attenuated reflections fobs**2 *UP* to the unattenuated
> fabs**2 I would
> assume that I have to multiply with the inverse of the
> B-factor attenuation,
> EXP(B*2*SINTH**2/L**2)
>
> If I look at the plot, then plot is indeed from a graph
> ln[(fobs**2)/fabs**2] = ln(k)-2B(sintol**2)
>
> thus
>
> ln(fobs**2)=ln(fabs**2)+ln(k)-2B(sintol**2) =
>
> fobs**2 =k*(fabs**2)*exp(-2B(sintol**2))
>
> which essentially is the opposite of what truncate says,
> I thus wonder if the inverse expression for bringing
> relative to absolute intensities, i.e., scaling back
> should be in truncate terms
>
> F(absolute)**2 = SCALE*F(observed)**2*EXP(B*2*SINTH**2/L**2)
>
> I know this is for sure the right way to bring
> fobses back up to unitary Us and normalized Es.
>
> What am I missing here?
>
> Thx, br
> --------------------------------------------
> Bernhard Rupp
> www.ruppweb.org
> --------------------------------------------
>
>
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