guidelines for authors of Rietveld refinement papers

[von dreele]

These notes are provided for authors who wish to submit a paper describing the results of Rietveld refinement of a structural model against powder diffraction data to any of the IUCr journals. They should be read in conjunction with the current version of the Notes for Authors for the relevant journal.

Powder CIFs

The results of the Rietveld refinement and the powder diffraction data should be provided in Crystallographic Information File (CIF) format. For Acta Crystallographica Sections C and E, enter the text of your paper in the CIF that contains the results. For other journals, prepare your paper as directed by the relevant Notes for Authors and submit the CIFs containing the results of the Rietveld refinement and the powder diffraction data when you are asked to do so during the online submission procedure.

How to prepare your CIF

A CIF contains a list of data items and their associated values. The formal definition of each data item is given in a CIF dictionary. The data items that are specific to powder studies all start _pd (for example, _pd_proc_ls_profile_function) and are defined in the powder CIF dictionary. Data items that can be used to describe a single-crystal or a powder study (for example, _cell_length_a) are defined in the core CIF dictionary. Data items that are not relevant to the study do not need to be included in the CIF.

The following items are provided to help you prepare a powder CIF for a Rietveld study:

Figures

Figures which present the experimental and calculated diffraction profiles of the material studied should also contain the difference between these profiles. Your paper should include a figure with the experimental, calculated and difference profiles and the corresponding data should be supplied in CIF format.  Where a large number of refinements with similar data are presented, a single figure for a typical fit may be provided.
 

Powder diffraction data

The primary diffraction data (i.e. the numerical intensity or counts at each measured point on the profile as a function of scattering angle or time-of-flight) should be supplied in CIF format. If the data set was reduced in size by summing together multiple measurements before it was analysed, the reduced data set (together with computed and difference values) should also be supplied. If the data have been scaled or do not follow pulse-counting statistics (for example, data from image-plate detectors), please include standard intensities. The diffraction data will be used during the review process and will be made available to readers through Crystallography Journals Online when your paper is published. They will also be archived by the IUCr.

We recommend that the data you submit include information corresponding to each item (1) to (5) in the following list:

(1) The data corresponding to the ordinate of your Rietveld refinement plot (e.g. two theta values, neutron time of flight etc.). Note that two theta values can be listed in full or can be specified by giving two theta(min), two theta(max) and the step size.

(a) CIF data names suitable for diffractometer data are:
_pd_meas_2theta_range_min, _pd_meas_2theta_range_max, _pd_meas_2theta_range_inc
_pd_meas_2theta_scan
_pd_proc_2theta_range_min, _pd_proc_2theta_range_max, _pd_proc_2theta_range_inc
_pd_proc_2theta_corrected
_pd_proc_d_spacing
_pd_proc_recip_len_Q
(Two theta values must be given.  d-spacings and Q values are not required, but it can be helpful to readers to include them.)

(b) CIF data names suitable for time-of-flight data are:
_pd_meas_time_of_flight
_pd_proc_wavelength
_pd_proc_d_spacing
_pd_proc_recip_len_Q
(The use of  _pd_meas_time_of_flight and either _pd_proc_d_spacing or _pd_proc_recip_len_Q is strongly recommended.)

(c) CIF data names for other kinds of data (energy-dispersive, camera etc.) include:
_pd_meas_position
_pd_proc_energy_incident
_pd_proc_d_spacing
_pd_proc_recip_len_Q
(The use of _pd_proc_d_spacing or _pd_proc_recip_len_Q in addition to _pd_meas_position or _pd_proc_energy_incident is strongly recommended.)

(2) The observed (or processed) intensity values: CIF data names are:
_pd_meas_counts_total
_pd_meas_intensity_total
_pd_proc_intensity_total
_pd_proc_intensity_net
(If _pd_meas_counts_total is not used, standard uncertainties should be specified or least-squares weights should be included.)

(3) Details of the background. CIF data names are:
_pd_meas_counts_background
_pd_meas_counts_container
_pd_meas_intensity_background
_pd_meas_intensity_container
_pd_proc_intensity_bkg_calc
_pd_proc_intensity_bkg_fix

(4) Rietveld refinements are almost always weighted by the reciprocal of the intensity values or the reciprocal of the intensity standard uncertainties squared (used the code `sigma' for _refine_ls_weighting_scheme to indicate this). If any other weighting has been used, this should specified by using the code `calc' for _refine_ls_weighting_scheme and details of the scheme used should be given in _refine_ls_weighting_details.

(5) The calculated pattern (CIF data names _pd_calc_intensity_net or _pd_calc_intensity_total).


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