Well according to Google this paper (JCS, 1936) contains the phrase
"magnitudes of the structure amplitude factors (F)":

http://www.google.co.uk/search?hl=en&q=%22magnitudes+of+the+structure+am
plitude+factors%22&btnG=Search&meta= .

It seems that "structure amplitude factor" is what we have now
abbreviated to "structure factor", i.e. it would appear that "amplitude"
was being used in a different sense from what we are using.  Logically
the magnitude of a structure amplitude factor should be a "structure
amplitude factor magnitude", so I guess it was not surprising that it
was abbreviated to just "structure amplitude".  I hardly think you could
call it a "structure amplitude factor amplitude"!

-- Ian

> -----Original Message-----
> From: owner-ccp...@jiscmail.ac.uk 
> [mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of Bernhard Rupp
> Sent: 12 January 2009 17:44
> To: CCP4BB@JISCMAIL.AC.UK; sa...@igbmc.fr
> Subject: Re: [ccp4bb] structure (factor) amplitude
> 
> Hmmm.....
> 
> Sacha just threw another wrench into that discourse. Seems we are
> also faced with a duality problem here:
> 
> Coming from a mathematical point of view treating F as a 
> complex number,
> 
> structure factor magnitude or 
> structure factor modulus
>  
> is more logical and more direct.
> 
> If you are taking the physical pov (let's not go into detail 
> there, btw)
> *interpreting* the complex number as wave description
> (and here I must say Ian's point wrt song title/name is well taken)  
> 
> structure factor amplitude 
> 
> is more logical.
> 
> Best, BR
> 
> Dear Bernhard,
> 
> First of all, happy new year !
> 
>  > I am getting conflicting comments on the use of
>  > 'structure factor amplitude'
>  > vs. just
>  > 'structure amplitude' for |F|.
> 
> Even when "structure factor amplitude" (or "magnitude", 
> following some 
> english-speaking persons?? If I am right I learned that 
> M.Woolfson prefers 
> "magnitude". My English is too poor to judge) seems to be 
> long, it seems to 
> be correct and have a clear meaning. That is not the case for 
> "structure 
> amplitude". In that sens I agree with Ethan and Pavel.
> 
> With best wishes !
> 
> Sacha
> 
> 


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