Gerard,
You are absolutely right. My apology for the confusion. Keep on
reading, looks like that James called |F| "geometrical structure
factor", which probably is not commonly used anymore.
-- Jianghai
On Jan 12, 2009, at 1:45 PM, Gerard Bricogne wrote:
> Dear Jacob and Jianghai,
>
> The trouble with this "King James version" is that what he calls
> the
> "structure amplitude" A is the amplitude of the scattered
> electromagnetic
> wave! If you look at equation (2.3) on p.27, the expression for A is
> first
> of all complex (!), and refers for each atom to its "scattering
> power",
> denoted phi[j]. This phi[j] is subsequently expressed in equation
> (2.11) in
> terms of some physical constants, of the squared atomic form factor,
> and of
> the polarisation factor, allowing A to be written in terms of the
> "structure
> factor" F defined in the familiar manner and of these other factors.
>
> Therefore, what Ewald and James call the "structure amplitude"
> is NOT
> AT ALL the amplitude (or modulus) of the structure factor, and
> therefore
> these venerable authors cannot be brought into the debate in this way!
>
>
> With best wishes,
>
> Gerard.
>
> --
> On Mon, Jan 12, 2009 at 12:58:27PM -0500, Jianghai Zhu wrote:
>> JPK beats me on this one. Here is the quote from R. W. James, "The
>> Optical
>> Principles of the Diffraction of X-rays".
>>
>> "We shall call A the 'structure amplitude', a name introduced by
>> Ewald, to
>> denote the fact that its value depends essentially on the structure
>> of the
>> group associated with each lattice-point. It is the amplitude, at
>> unit
>> distance, of the wave scattered by the unit group of s points."
>>
>> -- Jianghai
>>
>> ++++++++++++++++++++
>> Jianghai Zhu, PhD
>> Immune Disease Institute
>> Dept. of Pathology
>> Harvard Medical School
>> 3 Blackfan Circle, CLSB
>> Boston, MA 02115
>> Tel: 617-713-8224
>> Fax: 617-713-8232
>> ++++++++++++++++++++
>>
>>
>>
>>
>>
>>
>>
>> On Jan 12, 2009, at 12:43 PM, Jacob Keller wrote:
>>
>>> [King?] James says "structure amplitude."
>>>
>>> (1950 ed., Ch II, 1a (p27))
>>>
>>> JPK
>>>
>>> *******************************************
>>> Jacob Pearson Keller
>>> Northwestern University
>>> Medical Scientist Training Program
>>> Dallos Laboratory
>>> F. Searle 1-240
>>> 2240 Campus Drive
>>> Evanston IL 60208
>>> lab: 847.491.2438
>>> cel: 773.608.9185
>>> email: [log in to unmask]
>>> *******************************************
>>>
>>> ----- Original Message ----- From: "Ethan Merritt"
>>> <[log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Monday, January 12, 2009 10:59 AM
>>> Subject: Re: [ccp4bb] structure (factor) amplitude
>>>
>>>
>>>> On Monday 12 January 2009 02:42:43 Ian Tickle wrote:
>>>>
>>>>> 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.
>>>>
>>>> The field of crystagooglography is relatively young,
>>>> and standard procedures have not yet been established :-)
>>>> Here's what I get:
>>>>
>>>> +"structure factor amplitude" 18,000 hits
>>>> +"structure amplitude" 17,100 hits
>>>>
>>>> Ethan
>>>>
>>>>
>>>>>
>>>>> Cheers
>>>>>
>>>>> -- Ian
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: [log in to unmask]
>>>>>> [mailto:[log in to unmask]] On Behalf Of Pavel Afonine
>>>>>> Sent: 11 January 2009 03:01
>>>>>> To: Ethan A Merritt
>>>>>> Cc: [log in to unmask]
>>>>>> 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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>>>>
>>>>
>>>>
>>>> --
>>>> Ethan A Merritt
>>>> Biomolecular Structure Center
>>>> University of Washington, Seattle 98195-7742
>>>
>>
>
> --
>
> ===============================================================
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> * Gerard Bricogne [log in to unmask] *
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