Not only in Stout & Jensen but also in Blundell & Johnson 1976, Jan
Drenth's book and many more use "structure amplitude".
I like to think that "structure amplitude" (would not dare to call it
"slang") is the crystallographers short form of "structure factor
amplitude".
Although all of us know what is meant, for a novice to the field (and
the broader audience) "structure factor amplitude" would be the correct
term to use.
- J. -
Sue Roberts wrote:
My preference is also for the full structure factor amplitude. I
would have said that I'd never seen the term structure amplitude used.
However, I just looked this up in my old Stout & Jensen (1968 edition
- brown cover) and find that (on p. 195) where |F| is introduced they
define it as: 'the most important quantity derived from the
intensities is the /structure factor modulus (structure amplitude)/.
(Italics are theirs, not mine).
Sue
On Jan 12, 2009, at 8:37 AM, Andrew Purkiss-Trew wrote:
On Mon, 2009-01-12 at 10:42 +0000, Ian Tickle wrote:
I was taught 'structure amplitude' - makes perfect sense to me! Why
does 'structure amplitude' make any less sense than 'structure factor'?
It also clearly made sense to Phil Coppens, a crystallographer of
considerable repute, see ITC Vol. B (2nd Ed.), sect 1.2., p.10: 'The
Structure Factor'. To quote the introduction to the section: "The
'structure factor' is the central concept in structure analysis by
diffraction methods. Its modulus is called the 'structure amplitude'".
Also I did a 'Google vote' for the two terms. 'Structure amplitude' has
11300 hits. 'Structure factor amplitude' has only 4750. So all round I
would say that 'structure amplitude' wins by a considerable margin.
Having had a quick look at the google results myself, I think that there
is a problem is the methodology. Google doesn't take into account
punctuation when searching. So the first search includes results such as
'structure. Amplitude', where the two words are in different sentences,
or 'structure, amplitude' where the words are part of a list. Given this
case, the winning margin is likely to be less.
My preference would also be for the full 'Structure factor amplitude'.
'Structure amplitude' leaves me with visions of comparing the pdb files
of a small single domain protein and a ribosome. Two structures having
different sizes (or amplitudes).
Cheers
-- Ian
-----Original Message-----
From: owner-ccp...@jiscmail.ac.uk <mailto:owner-ccp...@jiscmail.ac.uk>
[mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of Pavel Afonine
Sent: 11 January 2009 03:01
To: Ethan A Merritt
Cc: CCP4BB@jiscmail.ac.uk <mailto:CCP4BB@jiscmail.ac.uk>
Subject: Re: [ccp4bb] structure (factor) amplitude
On 1/10/2009 5:14 PM, Ethan A Merritt wrote:
On Saturday 10 January 2009, Bernhard Rupp wrote:
Dear All,
I am getting conflicting comments on the use of
'structure factor amplitude'
vs. just
'structure amplitude'
for |F|.
???
That's just... odd.
|F| is the amplitude of F.
But no way F is a "structure".
I agree. If F is a structure factor then |F| is a structure
factor amplitude. "structure amplitude" doesn't make much sense...
Pavel.
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