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Transfer from msCIF: refine_ls_class category
- To: Multiple recipients of list <coredmg@iucr.org>
- Subject: Transfer from msCIF: refine_ls_class category
- From: Brian McMahon <bm@iucr.org>
- Date: Tue, 4 Aug 1998 11:13:32 +0100 (BST)
David has also suggested that the REFINE_LS_CLASS category in the modulated
structures dictionary should be moved lock, stock and barrel to the core:
#####################
## REFINE_LS_CLASS ##
#####################
data_refine_ls_class_[]
_name '_refine_ls_class_[]'
_category category_overview
_type null
loop_ _example
_example_detail
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
;
loop_
_refine_ls_class_R_factor_gt
_refine_ls_class_code
0.057 'Main'
0.074 'Com'
0.064 'NbRefls'
0.046 'LaRefls'
0.112 'Sat1'
0.177 'Sat2'
;
;
Example 1 - extracted from van Smaalen [(1991). J. Phys.:Condens. Matter 3,
1247-1263.]
;
# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
_definition
; Data items in the REFINE_LS_CLASS category record details
(for each reflection class separately) about the reflections used
for the structure refinement. Each reflection class is normally
defined by the number m=sum|mi|, where the mi are the integer
coefficients that, in addition to h,k,l, index the corresponding
diffraction vector in the basis defined in
_cell_reciprocal_basis. However reflection classes
could be defined, if convenient, in a more general and flexible
way.
;
data_refine_ls_class_d_res_high
_name '_refine_ls_class_d_res_high'
_category refine_ls_class
_type numb
_list yes
_list_reference '_refine_ls_class_code'
_enumeration_range 0.0:
_units A
_units_detail 'Angstroms'
_definition
; For each reflection class, the highest resolution in angstroms
for the spacing in the reflections used in refinement. This is
the lowest d value in a reflection class.
;
data_refine_ls_class_d_res_low
_name '_refine_ls_class_d_res_low'
_category refine_ls_class
_type numb
_list yes
_list_reference '_refine_ls_class_code'
_enumeration_range 0.0:
_units A
_units_detail 'Angstroms'
_definition
; For each reflection class, the lowest resolution in angstroms
for the spacing in the reflections used in refinement. This is
the highest d value in a reflection class.
;
data_refine_ls_class_R_factor_
loop_ _name '_refine_ls_class_R_factor_all'
'_refine_ls_class_R_factor_gt'
_category refine_ls_class
_type numb
_list yes
_list_reference '_refine_ls_class_code'
_enumeration_range 0.0:
_definition
; For each reflection class, the residual factors for all
reflections, and for significantly intense reflections (see
_reflns_threshold_expression) and included in the refinement.
The reflections also satisfy the resolution limits established by
_refine_ls_class_d_res_high and _refine_ls_class_d_res_low.
This is the conventional R factor.
R=sum|F(obs)-F(calc)|/sum|F(obs)|
F(obs)=the observed structure-factor amplitudes, F(calc)=the
calculated structure-factor amplitudes, and the sum is taken over
the specified reflections. See also
_refine_ls_class_wR_factor_all definitions.
;
data_refine_ls_class_R_Fsqd_factor
_name '_refine_ls_class_R_Fsqd_factor'
_category refine_ls_class
_type numb
_list yes
_list_reference '_refine_ls_class_code'
_enumeration_range 0.0:
_definition
; For each reflection class, the residual factor R(F^2^) calculated
on the squares of the observed and calculated structure factors,
for the reflections judged significantly intense (i.e. satisfying
the threshold specified by _reflns_threshold_expression) and
included in the refinement. The reflections also satisfy the
resolution limits established by _refine_ls_class_d_res_high and
_refine_ls_class_d_res_low.
R(F^2^)=sum|F(obs)^2^-F(calc)^2^|/sum|F(obs)^2^|
F(obs)^2^=squares of the observed structure-factor amplitudes,
F(calc)^2^=squares of the calculated structure-factor amplitudes,
and the sum is taken over the specified reflections.
;
data_refine_ls_class_R_I_factor
_name '_refine_ls_class_R_I_factor'
_category refine_ls_class
_type numb
_list yes
_list_reference '_refine_ls_class_code'
_enumeration_range 0.0:
_definition
; For each reflection class, the residual factor R(I) for
estimated reflection intensities, for the reflections judged
significantly intense (i.e. satisfying the threshold specified
by _reflns_threshold_expression) and included in the refinement.
This is most often calculated in Rietveld refinements
of powder data, where it is referred to as R~B~ or R~Bragg~
R(I)=sum|I(obs)-I(calc)|/sum|I(obs)|
I(obs)=the net observed intensities, I(calc)=the net calculated
intensities, and the sum is taken over the specified reflections
;
data_refine_ls_class_wR_factor_all
_name '_refine_ls_class_wR_factor_all'
_category refine_ls_class
_type numb
_list yes
_list_reference '_refine_ls_class_code'
_enumeration_range 0.0:
_definition
; For each reflection class, the weighted residual factors for all
reflections and included in the refinement. The reflections also
satisfy the resolution limits established by
_refine_ls_class_d_res_high and _refine_ls_class_d_res_low.
wR=sum|w|Y(obs)-Y(calc)|^2^|^1/2^/sum|wY(obs)^2^|
Y(obs)=the observed amplitude specified by
_refine_ls_structure_factor_coef, Y(calc)=the calculated
amplitude specified by _refine_ls_structure_factor_coef, w=the
least-squares weight, and the sum is taken over the specified
reflections. See also _refine_ls_class_R_factor_ definitions.
;
data_refine_ls_class_code
_name '_refine_ls_class_code'
_category refine_ls_class
_type char
_list yes
_list_link_parent '_diffrn_reflns_class_code'
loop_ _example '1'
'm1'
's2'
_definition
; The code identifying a certain reflection class. This code must
match a _diffrn_reflns_class_code.
;
_______________________________________________________________________________
Brian McMahon tel: +44 1244 342878
Research and Development Officer fax: +44 1244 314888
International Union of Crystallography e-mail: bm@iucr.ac.uk
5 Abbey Square, Chester CH1 2HU, England bm@iucr.org
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