notes for authors

IUCrData is a peer-reviewed open-access data publication from the International Union of Crystallography (IUCr). It aims to provide short descriptions of crystallographic datasets and datasets from related scientific disciplines, as well as facilitating access to the data. The primary article category is Data Reports; these describe crystal structures of inorganic, metal-organic or organic compounds. Information on each crystal structure includes the crystallographic data (CIF and structure factors), a data validation report, figures and a text representation of the data.

1. Categories of submission

IUCrData currently publishes a single category of data articles.

1.1. Data Reports

Data Reports provide brief descriptions of the crystal structure of a single inorganic, metal-organic or organic compound.

2. Submission requirements

2.1. Data article preparation

Guidelines for the preparation and editing of a data article are available from the online author help page at http://iucrdata.iucr.org/x/services/authorservices.html. All data articles must be submitted in Crystallographic Information File (CIF) format. A free CIF editor for authors, publCIF, may be obtained from http://publcif.iucr.org. An online version of publCIF is also available.

Authors are required to validate their CIF and structure factors using the checkCIF service at http://iucrdata.iucr.org/services/cif/checking/checkfull.html. Validation alerts returned by checkCIF should be resolved where possible before proceeding. In some cases, a validation response form (VRF) will be supplied by checkCIF. If the related validation issue cannot be resolved, this form should be completed as described in the online author help page at http://iucrdata.iucr.org/x/services/authorchecklist.html, preferably with the addition of appropriate explanatory text in the experimental section of the CIF. A preview of the CIF may be generated using the printCIF service at http://iucrdata.iucr.org/services/cif/printcif.html or by using publCIF.

The Main Editors, Co-editors and Editorial Office staff are available to assist authors with any technical matters.

2.2. Method of submission

Full details of the submission procedure can be found at http://iucrdata.iucr.org/x/services/helpsubmit.html. Data articles should be submitted at http://iucrdata.iucr.org/x/services/submit.html or via the online publCIF interface.

During the submission procedure, authors will be required to submit additional electronic files; these include a chemical scheme (see §3.2.4[link]), diagrams to be included in the publication (see §3.2.5[link]) and structure factors (see §3.2.6[link]) or powder diffraction data. Authors will also be asked to agree to an open-access licence (see §2.7[link]). In addition, they will also be asked to confirm that they can pay the open-access fee, or that they have a payment waiver (see §7.5[link]).

On completion of the submission, each data article will be assigned an Editorial Office refcode. The refcode has two letters and four digits (e.g. hb3127), and should be used in all subsequent communications with the Editorial Office and Co-editor.

2.3. Handling of data articles

All contributions will be seen by the Main Editors before peer review. The Main Editors will decide whether data articles are considered for publication, or are rejected without further review.

Data articles considered suitable for peer review will be assigned to a Co-editor. The Co-editor is responsible for the review steps and future communications with the authors up to the acceptance stage.

Once a data article is accepted, it is the responsibility of the Managing Editor to prepare the data article for publication and to correspond with the authors and/or the Co-editor to resolve outstanding issues. The date of acceptance that will appear on the published data article will be the date on which the Managing Editor receives the last item needed. The Main Editors review all accepted data articles and reserve the right to request or make appropriate changes to ensure conformity with IUCrData standards; in the unlikely event of significant changes being required at this stage, the authors will be contacted promptly.

All communications will be sent electronically to the e-mail address provided on submission. Failure to respond to a communication from either a Co-editor or the Editorial Office staff within one month will result in the automatic withdrawal of the data article.

2.4. Revisions

After initial submission, revised or new files should only be uploaded when requested by the Co-editor. Revisions should be supplied promptly. Further revisions may be requested before acceptance of the submission. If a data article is not acceptable after two revision cycles, it will not be considered further.

2.5. Author's warranty

The submission of a data article is taken as an implicit guarantee that the work is original, that it is the author(s) own work, that all authors are aware of and concur with the submission, that all workers involved in the study are listed as authors or given proper credit in the acknowledgements, that the data article has not already been published (in any language or medium), and that it is not being considered and will not be offered elsewhere while under review. The inclusion of material in an informal publication, e.g. a preprint server or a newsletter, does not preclude publication in IUCrData.

The co-authors of a data article should be all those persons who have made significant scientific contributions to the work reported, including the ideas and their execution, and who share responsibility and accountability for the results. Other contributions should be indicated in the acknowledgements. Changes to the list of authors will normally require the agreement of the editor and all authors.

The IUCr is a member of COPE (Committee on Publication Ethics) and endorses its recommendations, including the Code of Conduct for Editors, which are available at http://www.publicationethics.org/. Important considerations related to publication have been given in the ethical guidelines published in Acc. Chem. Res. (2002), 35, 74–76 and Graf et al. [Int. J. Clin. Pract. (2007), 61(Suppl. 152), 1–26]. Authors are expected to comply with these guidelines.

2.6. Author grievance procedure

An author who believes that a data article has been unjustifiably treated by the Co-editor may appeal to the Main Editors for a new review. The appeal must be made within 3 months of rejection of the data article. The decision of the Editors is final.

2.7. Copyright

Authors will not be asked to transfer copyright to the IUCr, but will instead be asked to agree during submission to an open-access licence. This licence is identical to the Creative Commons Attribution (CC-BY) Licence. Details of author rights can be found at http://iucrdata.iucr.org/services/authorrights.html.

3. Publication requirements

The publication requirements for the text, tabular and graphical material are described in this section. The standards for numerical and codified data, and a list of all data items required for submission are available from the online author help page (see §7[link]).

3.1. Data Reports

Data Reports are extended abstracts each describing the structure of a single inorganic, metal-organic or organic compound. Data Reports should normally include the following text sections: Abstract, Structure description and Synthesis and preparation. The Refinement section will only be published if it reports non-routine procedures. A chemical scheme is published for metal-organic and organic compounds. Authors are required to supply an ellipsoid plot for molecular species and a polyhedral plot for inorganic compounds.

3.1.1. Title and authors

The Title should be short and informative, e.g. `Crystal structure of …'. The full first name of each author is preferred. All authors are encouraged to provide an ORCiD iD during submission. The e-mail address of the submitting author should be provided. This is the e-mail address which will be used for all subsequent communications with the authors, including despatch of electronic proofs. If the e-mail address of the submitting author is different from that of the corresponding author, only that of the corresponding author will appear in the published version of the data article.

3.1.2. Synopsis

A one or two sentence Synopsis of the main findings of the article should be supplied for inclusion in the Table of Contents.

3.1.3. Abstract and keywords

The Abstract must be written in English, be informative and should clearly and briefly summarize the most important aspects and results of the study. It should be capable of being understood on its own without access to the text or figures. The systematic IUPAC name of the studied compound should be given here if it is not included in the Title. The length of the Abstract should be 100–150 words. Authors should also supply at least three keywords.

3.1.4. Structure description

The Structure description section (CIF dataname _publ_manuscript_text) contains any comments about the structure. Overlap between this section and the Abstract should be kept to a minimum. Together they should include: a brief description of the molecule with salient features; a brief summary of the packing features; a related structure or structures for comparison; the relevance of the molecule or background to the study.

3.1.5. Synthesis and preparation

The description of the preparation of samples should give sufficient information on the isolation or synthesis of the compound, crystal preparation (method, solvents and their ratios), and identification (e.g. melting points, optical rotation), to reproduce the experiment. Previously reported syntheses, isolation procedures or spectroscopic data need only be cited.

3.1.6. Refinement

Details of the refinement will only be published if they include non-routine procedures such as twinning, disorder or excluded solvent, specific details of any restraints or constraints.

3.1.7. Acknowledgements

Acknowledgement should be given for any assistance provided to the study (see §2.5[link]). If diffraction data collection was not carried out by one of the authors, or in the laboratory of one of the authors, details of who collected the data and where the data collection was carried out should be provided.

3.1.8. References

References to published work must be cited in the format detailed in §6[link].

3.2. Other considerations

3.2.1. Atomic sites

Recommendations for defining atom coord­in­ates and atom labelling are given in the online author help page. See also §5.3[link].

3.2.2. Experimental data

Experimental data are extracted and tabulated automatically from the CIF. During tabulation, some numerical items may be formatted with a revised number of decimal places to conform to a consistent style.

Authors should include copies of their refinement instructions file(s) and input reflection data file(s), where available, in the submitted CIF (for more details, see the online author help page).

The latest version of the refinement software should be used, e.g. for SHELXL users this is currently SHELXL2014/7. Authors should include copies of their refinement instructions file(s) and input reflection data file(s), where available, in the submitted CIF (for more details, see the online author help page at http://iucrdata.iucr.org/x/services/authorchecklist.html). Co-editors may request any additional experimental data or material they feel necessary to complete a full review of the data article.

3.2.3. Geometry data and tables

All symmetry-unique bond lengths and angles, as well as those involving H atoms, should be included in the CIF; the additional inclusion of torsion angles for non-H atoms is encouraged. This is usually a selectable instruction in the refinement program. All geometry data will be placed in the supporting information available to readers.

Tables of bond lengths, angles and torsion angles will be generated automatically from parameters flagged for publication in the CIF. Values that are of special interest and are discussed in the text should be included in these tables. Tables of hydrogen bonds can similarly be created and can usually be generated by the refinement program. Other desired tables, such as a comparison of parameters, can be included using the extra table facility in publCIF or as described at http://iucrdata.iucr.org/x/services/cifinfo.html.

3.2.4. Chemical scheme

A chemical structure diagram (typical examples are shown below) must be included for all but inorganic compounds with extended framework structures. Authors are required to submit such diagrams electronically in one of the formats listed in §4[link]. The diagram should show all species present in the structure, including counter-ions and solvent molecules in their correct proportions. For polymeric structures, the connectivity to the next repeat units should be indicated. Any relative or absolute stereochemistry should be shown.

[Scheme 1]
[Scheme 2]

Authors are also encouraged to submit chemical connectivity (MOL, CML, CHM, SMI) files of reported structures; these can often be generated by the software used to generate the scheme.

3.2.5. Diagrams to be included in the publication

Diagram requirements are given in §4[link]. Carefully prepared diagrams can convey a wealth of information to the reader, so close attention to these is beneficial. For example, a well-presented displacement ellipsoid plot of a molecular compound will clearly show the stereochemistry and any unusual atomic displacements or disorder. The orientation of species depicted in crystallographic figures and chemical schemes should ideally correspond as closely as possible. For extended structures, the displacement ellipsoid plot should show at least the chemically unique fragment and the coordination environment of any metal atoms. Sufficient non-H atom labels should be included on the diagram to allow all atoms mentioned in the text to be identified. The labels should be consistent throughout the data article.

Authors may also supply additional diagrams, such as packing diagrams, showing extended structures or intermolecular interactions or diagrams depicting non-crystallographic information, e.g. spectra. The clarity of packing diagrams can be increased by excluding H-atom sites not involved in hydrogen bonding or other discussed interactions. Packing diagrams should show the unit-cell outline with labelled origin and cell-axis directions, or the orientation of the cell axes should be given in a legend at the side.

3.2.6. Structure factors

The reflection data h, k, l, Ymeas, σYmeas, Ycalc (where Y is I, F2 or F), must be supplied in CIF format during the submission process (note that if structure factors are embedded in the CIF, separate structure factor files are not required). All unique reflections should be included. Authors are also encouraged to provide the reflection data file used as input to the refinement program (see §3.2.2[link]).

3.2.7. Standard uncertainties

The standard uncertainty (abbreviated s.u.) should be expressed as a number in parentheses following the numerical result and should be on the scale of the least significant digits of the result and usually in the range 2–19.

3.2.8. Absolute structure

Absolute structure is relevant in any non-centrosymmetric space group. The method applied should be described and a literature citation and the number of Friedel pairs used in the determination of the absolute structure parameter should be provided. For more information, see Flack [Acta Cryst. (2012), C68, e12–e13], Flack & Bernardinelli [Acta Cryst. (1999), A55, 908–915; J. Appl. Cryst. (2000), 33, 1143–1148] and Flack, Sadki, Thompson & Watkin [Acta Cryst. (2011), A67, 21–34].

4. Guidelines for preparing figures and multimedia content

A set of guidelines for preparing figures is available from http://iucrdata.iucr.org/x/services/help/artwork/guide.html. Figures and chem­ical structure schemes (see §3.2.4[link] for a typical example) should be prepared in HPGL, PostScript, encapsulated PostScript, TIFF or PNG format. The resolution of bitmap graphics should be a minimum of 600 d.p.i.

Diagrams should be submitted via the web submission interface (see §2.2[link]).

4.1. Size, lettering and symbols

Diagrams will normally be sized by the Editorial Office staff so that the greatest width including lettering is less than 8.8 cm. Fine-scale details and lettering must be large enough to be clearly legible (ideally 1.5–3 mm in height) after the whole diagram has been reduced to this width.

The labels for symmetry-related atoms in displacement ellipsoid plots should contain additional symbols or letters to depict the symmetry operation (e.g. C5i is preferred, but C5#, C5A or similar may be used) and the figure caption should define the corresponding symmetry operations. The atom labels should not be unduly obscured by other lines in the diagram.

4.2. Figure numbering and captions

Diagrams should be numbered in a single series in the order in which they are referred to in the text. Figure captions should describe briefly the key features that are being depicted in the diagram, state the ellipsoid probability used if it is a displacement ellipsoid diagram and define any symmetry operations referred to by the atom labels.

4.3. Video and multimedia content

Multimedia content (e.g. time-lapse sequences, three-dimensional structures) is welcomed.

4.4. Funding information

Articles may include a Funding information section. This section aims to help authors comply with the reporting requirements of funders, and includes information on funders and grant/award numbers. Funding information should not be included in the Acknowledgements section. For more information, see http://journals.iucr.org/services/funding.html.

5. Nomenclature

5.1. Units

The International System of Units (SI) is used except that the ångström (symbol Å, defined as 10–10 m) is generally preferred to the nanometre (nm) or picometre (pm) as the appropriate unit of length. Recommended prefixes of decimal multiples should be used rather than `×10n'.

5.2. Nomenclature of chemical compounds

Names of chemical compounds and minerals should conform to the nomenclature rules of the International Union of Pure and Applied Chemistry (IUPAC), the International Union of Biochemistry and Molecular Biology (IUBMB), the International Mineralogical Association (IMA) and other appropriate bodies. Any accepted trivial or nonsystematic name may be retained, but the corresponding systematic (IUPAC) name should also be given.

For crystal structures containing chiral molecules, authors should make it clear whether the crystal structure is a racemate or enantiopure, and if enantiopure whether or not the assignment of the absolute configuration is justified. The title, com­pound name, chemical diagrams, atomic coordinates and space group must correspond with the enantiomeric composition and the selected configuration.

Authors may find nomenclature programs such as Marvin (http://www.chemaxon.com/products/marvin) and ACD/ChemSketch (http://www.acdlabs.com/products/draw_nom/draw/chemsketch) to be useful resources when naming compounds.

5.3. Crystallographic nomenclature

Authors should follow the general recommendations produced by the IUCr Commission on Crystallographic Nomenclature (see reports at http://www.iucr.org/iucr/commissions/cnom.html).

The symmetry-unique atoms in the refinement model should be identified by unique labels composed of a number appended to the IUPAC chemical symbol (e.g. Zn1, C7 etc.). Chemical and crystallographic numbering should be in agreement wherever possible. Atom labels should be as concise as possible and avoid superfluous characters, e.g. C2 is better than C02. H-atom numbers should relate to the atom to which they are bonded.

Atoms in positions related by a symmetry operation to the positions defined in the refinement model should be identified in the text with lower-case Roman numeral superscripts appended to the original atom labels and the symmetry operators defined [e.g. C5i; symmetry code: (i) −x + ½, y − ½, −z + ½]. For the labelling of symmetry-related atoms in diagrams, see §4.1[link].

Space groups should be designated by the Hermann–Mauguin symbols. In triclinic systems, the reduced cell should be used, and for other crystal systems, the standard cell settings, as listed in Volume A of International Tables for Crystallography, should be used unless objective reasons to the contrary are stated. Note that space group settings like P21/n and I2/a are usually preferable to P21/c and C2/c, respectively, when the former lead to unit cell β angles that are closer to 90° than the latter. If there is a choice of origin, this should be stated in the refinement section. The choice of axes should normally follow the recommendations of the Commission on Crystallographic Data [Kennard et al. (1967). Acta Cryst. 22, 445–449].

6. References

The publCIF editor (see §2.1[link]) allows the consistency of references and citations to be checked.

References to published work must be indicated in the text by giving the authors' names followed immediately by the year of publication, e.g. Neder & Schulz (1999) or (Neder & Schulz, 1999). Where there are three or more authors, the citation in the text should be indicated in the form Smith et al. (1989) or (Smith et al., 1989) etc.

Identification of individual structures in the data article by use of database reference (identification) codes should be accompanied by a full citation of the original literature in the reference list. Citations in supporting information should also appear in the main body of the data article.

In the reference list, all authors and inclusive page numbers must be given. Entries for journals, books, multi-author books, computer programs and personal communications should be arranged alphabetically and conform with the following style:

Benedict, J. B., Graber, T., Scheins, S., Kaminski, R., Henning, R., Sheng, Y.-S. & Coppens, P. (2017). In preparation.

Bond, A. D. (2012). Acta Cryst. E68, o1992–o1993.

Collaborative Computational Project, Number 4 (1994). Acta Cryst. D50, 760–763.

CRC Handbook of Chemistry and Physics (1983). 64th ed., edited by R. C. Weast, p. D-46. Boca Raton: CRC Press.

International Union of Crystallography (2014). (IUCr) Structure Reports Online, http://journals.iucr.org/.

Keller, E. & Pierrard, J.-S. (1999). SCHAKAL99. University of Freiburg, Germany.

Khoshouei, M., Radjainia, M., Baumeister, W. & Danev, R. (2016). bioRxiv, https://doi.org/10.1101/087841.

Satomura, T., Sakuraba, H., Hara, Y. & Ohshima, T. (2010). Acta Cryst. F66, doi:10.1107/S1744309110036808.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Shmueli, U. & Weiss, G. H. (1985). Structure and Statistics in Crystallography, edited by A. J. C. Wilson, pp. 53–66. Guilderland: Academic Press.

Smith, J. M. (2004). Personal communication.

Wall, M. E. (2015). arXiv:1511.07811.

Zhou, P. F. (1993). PhD thesis, McMaster University, Hamilton, Ontario, Canada.

7. Author information and services

Full details of guidelines for the preparation and editing of data articles, the data items required, standard data codes and keywords, CIF templates, example CIFs, and data-validation criteria and procedures can be found via the online CIF help page at http://iucrdata.iucr.org/x/services/cifinfo.html.

7.1. Author tools

A number of tools are available to help with the preparation of data articles.

(a) The checkCIF/PLATON service at http://iucrdata.iucr.org/services/cif/checking/checkfull.html allows CIFs and structure factors to be checked.

(b) Data articles can be edited using publCIF, available from http://publcif.iucr.org.

(c) A preview of a data article may be printed using the printCIF service at http://iucrdata.iucr.org/services/cif/printcif.html.

7.2. Status information

Authors may obtain information about the current status of their data article at http://iucrdata.iucr.org/services/status.html.

7.3. Proofs

Proofs will be provided electronically in portable document format (pdf). The contact author will be notified by e-mail when the proofs are ready for downloading (see §2.3[link]).

7.4. Reprints

After publication, the contact author will be able to download the electronic reprint of the published data article, free of charge. Authors will also be able to order printed reprints at the proof stage.

7.5. Open access

IUCrData is an open-access data publication. The costs of peer review, of production, and of online hosting and archiving will be met by charging an open-access fee to authors.

Authors will be asked to pay an open-access fee upon acceptance of their data article for publication. Authors from developing countries may apply for their open-access fees to be waived. Waiver requests must be made before submission of a data article. Full details of the open-access arrangements for IUCrData are available at http://iucrdata.iucr.org/services/oa/openaccess_x.html.

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