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James.
(message from core DMG chair follows)
Dear Colleagues,
Last September I circulated for fast track approval a recommendation for adding a new item:
_diffrn_radiation_wavelength_nominal,
to the core dictionary (see below for details). The intent was that this could be used for giving a nominal wavelength calculated e.g., from the parameters of a diffractometer. It was proposed that this might be needed for completeness even though it was not accurate enough for calculating lattice parameters, etc. This proposal was passed by the core CIF dictionary maintenance group by default (no one raised any objection). When this proposal was subsequently presented for final approval to COMCIFS, Nick Spadaccini suggested a more elegant alternative, namely that by adding instead the item
_diffrn_radiation_wavelength_determination
we could loop the nomiinal wavelength with the refined (and any other interesting) wavelengths. This would be more informative and allow for future expansion.
An example of how this might be used is:
loop_
_diffrn_radiation_wavelength_id
_diffrn_radiation_wavelength
_diffrn_radiation_wavelength_determinaton
1 1.23456 fundamental
2 1.25 estimated
According to our rules, this proposal was posted for comment to the coreCIF dictionary maintenance group for six weeks. Two comments were received, neither raising any serious objection
David Brown
Chair Core CIF Dictionary Maintenance Group
COMMENTS FROM CORE CIF DICTIONARY MANAGEMENT GROUP
--------------------------------------------------
Comment from Jim Kaduk
I think this enumerated data item gets us to where we want to be. We
want to document the wavelength(s) used in the experiment, as well as
how it was determined. Knowing both, one could change/correct the
wavelength later if desired for some particular purpose.
Comment from R. Curtis Haltiwanger
Research Scientist
Cephalon, Inc.
610-738-6853
As I said I have only used lab sources, so I have not needed other wavelengths.
That makes it hard for me to comment on this further extension.
In general, I like including additional information.
Probably because of my lack of experiance this extension seems complicated to me.
I'll leave it to others to comment and evaluate.
PROPOSED DICTIONARY CODE
------------------------
Add new item to DDL1 Core CIF dictionary
data_diffrn_radiation_wavelength_determination
_name '_diffrn_radiation_wavelength_determination'
_category diffrn_radiation_wavelength
_type char
_list both
_list_reference '_diffrn_radiation_wavelength_id'
loop_
_enumeration
_enumeration_detail
'fundamental'
'Wavelength that is a fundamental property of matter e.g. MoK\alpha'
'estimated'
'Estimated from secondary information e.g. monochromator angle or time of flight'
'refined'
'Based on refinement using a standard material with known cell parameters'
_definition
; The method of determination of incident wavelength. Further information may be provided in _diffrn_radiation_special_details
;
Reply to: [list | sender only]
Revised fast-track proposal on wavelength passes DMG review
- To: "Discussion list of the IUCr Committee for the Maintenance of the CIFStandard (COMCIFS)" <comcifs@iucr.org>
- Subject: Revised fast-track proposal on wavelength passes DMG review
- From: James Hester <jamesrhester@gmail.com>
- Date: Tue, 12 Jan 2010 12:15:53 +1100
James.
(message from core DMG chair follows)
Dear Colleagues,
Last September I circulated for fast track approval a recommendation for adding a new item:
_diffrn_radiation_wavelength_nominal,
to the core dictionary (see below for details). The intent was that this could be used for giving a nominal wavelength calculated e.g., from the parameters of a diffractometer. It was proposed that this might be needed for completeness even though it was not accurate enough for calculating lattice parameters, etc. This proposal was passed by the core CIF dictionary maintenance group by default (no one raised any objection). When this proposal was subsequently presented for final approval to COMCIFS, Nick Spadaccini suggested a more elegant alternative, namely that by adding instead the item
_diffrn_radiation_wavelength_determination
we could loop the nomiinal wavelength with the refined (and any other interesting) wavelengths. This would be more informative and allow for future expansion.
An example of how this might be used is:
loop_
_diffrn_radiation_wavelength_id
_diffrn_radiation_wavelength
_diffrn_radiation_wavelength_determinaton
1 1.23456 fundamental
2 1.25 estimated
According to our rules, this proposal was posted for comment to the coreCIF dictionary maintenance group for six weeks. Two comments were received, neither raising any serious objection
David Brown
Chair Core CIF Dictionary Maintenance Group
COMMENTS FROM CORE CIF DICTIONARY MANAGEMENT GROUP
--------------------------------------------------
Comment from Jim Kaduk
I think this enumerated data item gets us to where we want to be. We
want to document the wavelength(s) used in the experiment, as well as
how it was determined. Knowing both, one could change/correct the
wavelength later if desired for some particular purpose.
Comment from R. Curtis Haltiwanger
Research Scientist
Cephalon, Inc.
610-738-6853
As I said I have only used lab sources, so I have not needed other wavelengths.
That makes it hard for me to comment on this further extension.
In general, I like including additional information.
Probably because of my lack of experiance this extension seems complicated to me.
I'll leave it to others to comment and evaluate.
PROPOSED DICTIONARY CODE
------------------------
Add new item to DDL1 Core CIF dictionary
data_diffrn_radiation_wavelength_determination
_name '_diffrn_radiation_wavelength_determination'
_category diffrn_radiation_wavelength
_type char
_list both
_list_reference '_diffrn_radiation_wavelength_id'
loop_
_enumeration
_enumeration_detail
'fundamental'
'Wavelength that is a fundamental property of matter e.g. MoK\alpha'
'estimated'
'Estimated from secondary information e.g. monochromator angle or time of flight'
'refined'
'Based on refinement using a standard material with known cell parameters'
_definition
; The method of determination of incident wavelength. Further information may be provided in _diffrn_radiation_special_details
;
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