notes for authors

2.1. Research Papers

Full-length Research Papers describe important original research work. They should not normally exceed 15 journal pages (about 15 000 words). Abstracts should provide the context of the study, the main findings and the broad significance of the results. These should be typically 250–300 words.

2.2. Lead Articles

Lead Articles are authoritative, comprehensive and forward-looking reviews of major areas of research interest. Suggestions for suitable topics and of potential author(s) are welcomed by the Section Editors. The Section Editors will discuss the treatment of the topic, the length of the article and the delivery date of the manuscript with invited author(s).

2.3. Feature Articles

Feature Articles are focused surveys covering recent advances in an area of current research. They should not aim to be comprehensive, but a brief introduction should provide historical perspective and a brief conclusion should indicate likely future directions. Inclusion of relevant new results is appropriate.

Feature Articles will generally be about ten journal pages (10 000 words). Shorter articles on rapidly evolving areas are also actively encouraged.

2.4. Topical Reviews

Topical Reviews aim to capture the current trend of a field and are expected to be relatively short. Typically they should contain about 6000 words and a maximum of 50 references, with half of those having been published in the last three years.

2.5. Letters to the editor

These may deal with non-technical aspects of crystallography, its role, its propagation, the proper function of its Societies etc., or may make a technical observation that would usefully be brought to a wider audience. Letters should be submitted to the Section Editors.

2.6. Scientific Comment

Comments of general scientific interest to the readership are welcomed. These should not normally exceed two journal pages.

2.7. Scientific Commentaries

Scientific Commentaries discuss articles of particular importance for the readership of the journal. Suggestions for suitable topics and of potential author(s) are welcomed by the Section Editors.

2.8. Special issues

Acta Crystallographica Section C also publishes focused special sections and issues devoted to all areas of structural chemistry. For more information contact the Section Editors.

3.1. Article preparation

Guidelines for the preparation of your article for submission and tools to help you do this, details of what to do about supporting information, and utilities to track the status of your article once it has been accepted and is in production are available from the online author help pages at https://journals.iucr.org/c/services/authorservices.html.

For those contributions reporting crystal structures or refinement strategies, a CIF containing at least the technical and numerical details of the structure(s) is required. The text of an article may be included in the CIF or provided as a separate Word document.

Authors preparing articles in Word format should use the templates available from https://journals.iucr.org/services/wordstyle.html, where full instructions are given.

For CIF submissions, a free editor, publCIF, may be obtained from https://publcif.iucr.org.

Authors are required to validate their CIF and structure factors using the checkCIF service at https://journals.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 pages at https://journals.iucr.org/c/services/authorchecklist.html, preferably with the addition of appropriate explanatory text in the published experimental section of the article. A preview of the CIF may be generated using the printCIF service at https://publcif.iucr.org/services/tools/printcif.php or by using publCIF.

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

3.2. Submission

Articles should be submitted at https://journals.iucr.org/c/services/submit.html. Full instructions for submitting an article and details of the files required are given at https://journals.iucr.org/c/services/submitinstructions.html. Authors are encouraged to use the templates available from https://journals.iucr.org/c/services/authorservices.html.

For structural articles, appropriate supporting information for each structure reported should be provided during submission (see Section 8).

A single author (the submitting author) should handle the submission of the article and be the contact for any editorial questions during the review and publication processes. The submitting author should provide an e-mail address. The published article may have one or more authors (correspondence authors) who are responsible for communications after publication and are marked with an asterisk in the published article. All authors are strongly encouraged to provide an ORCiD iD during submission.

During the submission procedure, authors will be required to submit additional electronic files; these include the chemical scheme (see Section 4.13), diagrams to be included in the publication (see Section 4.14) and structure factors (see Section 4.15) or powder diffraction data (see Section 4.16).

On completion of the submission procedure, each article will be assigned an Editorial Office refcode. The refcode has two letters and four digits (e.g. ln3127), and should be used in all subsequent communications with the Editorial Office and Co-editor.

All submissions should be accompanied by a covering letter that explains the significance of the work reported. During submission authors will be encouraged to provide a tweet about their article for use on publication; twitter handles for departments, institutions etc. will also be requested.

3.3. Handling of articles

Each article is handled by an editor (Co-editor or Section Editor) chosen by the author from a list of those available at the time of submission. Authors should choose an editor whose area of expertise most closely matches the subject of the article. Details of the current Editorial Board can be found at https://journals.iucr.org/c/services/editors.html.

All contributions will be seen by referees (normally two) before they can be accepted for publication. The editor to whom the article is assigned is responsible for choosing referees and for accepting or rejecting the article. This responsibility includes decisions on the final form of the article and interpretation of these Notes when necessary. The Co-editor may request revisions to the article (e.g. to the title and abstract) before peer review. Further information on the peer review process can be found at https://journals.iucr.org/c/services/peerreview.html.

Changes to an article requested by the Section Editors, Co-editor or the Editorial Office staff should be received within one month of transmittal to the author, otherwise the submission will be considered as withdrawn. If an article is not acceptable after two rounds of major revision it will not be considered further. Any subsequent communication of the material will be treated as a new submission in the editorial process. An article that has been rejected should not be resubmitted to any IUCr journal unless the reasons given for the rejection have been fully addressed in the revised version.

After initial submission, any revised or new files should be uploaded only in response to a specific request from an editor.

For accepted articles, it is the responsibility of the Managing Editor to prepare the article for publication. This may involve correspondence with the authors and/or the responsible editor in order to resolve ambiguities or to obtain satisfactory figures or tables. The date of acceptance that will appear on the published article is the date on which the Managing Editor receives the last item required. Correspondence will be sent to the submitting author unless the Managing Editor is informed of some other suitable arrangement. Contact details for the Managing Editor of Section C can be found at https://journals.iucr.org/services/contactus.html.

Articles may be checked for plagiarism using the Crossref Similarity Check service.

3.4. Transfer of articles

On rare occasions, editors may suggest the transfer of an article to another IUCr Journal, if the article appears to be more suited to the other journal. The transfer process is rapid, as articles can be seamlessly transferred from one journal to another together with the corresponding reviews. The editor of the new journal will often make a decision based on the existing reviews, but will sometimes invite additional reviewers. Note that any change to the journal of publication will only be made after full discussion with the submitting author.

3.5. Author's warranty and ethical considerations

The submission of an 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 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 consideration for an IUCr journal. The prior inclusion of material in an informal publication, e.g. a preprint server, is welcomed by IUCr Journals.

The co-authors of an 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 https://www.publicationethics.org/. Important ethical considerations related to publication have been given in the 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. Further details of the ethical policies of IUCr Journals can be found at https://journals.iucr.org/services/ethicalpublishingpolicy.html.

Authors publishing in the journal may be asked to review articles submitted to the journal.

3.6. Quality of writing

Articles should be clearly written and grammatically correct. If the Co-editor concludes that language problems would place an undue burden on the referee(s), the manuscript may be returned to the authors without review. Details of language-editing services can be found at https://journals.iucr.org/services/languageservices.html.

3.7. Author grievance procedure

An author who believes that an article has been unjustifiably treated by the Co-editor may appeal initially to the Section Editors for a new review and, finally, to the Editor-in-chief of IUCr journals if still aggrieved by the decision. The initial appeal should be made within three months of rejection of the article. The decision of the Editor-in-chief is final.

3.8. Licencing

Except as required otherwise by national laws, an author will be required to agree to either a licence to publish or an open-access licence (see Section 3.9) before a manuscript can be accepted. Details of author rights can be found at https://journals.iucr.org/services/authorrights.html.

3.9. Open access

Authors are given the opportunity to make their articles open access. Authors of open-access articles will not be asked to transfer copyright to the IUCr, but will instead be asked to agree to an open-access licence. This licence is identical to the Creative Commons Attribution (CC-BY) Licence. Further details can be found at https://journals.iucr.org/c/services/openaccess.html.

3.10. Publication fees

There are no fees for colour figures or electronic reprints. If authors require open access there is a charge and for some authors this may be covered by a transformative deal with their institution. Full details will be given at the proof stage or see https://journals.iucr.org/c/services/openaccess.html.

3.11. 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 https://journals.iucr.org/services/funding.html.

4.1. General information

Articles should be clearly and simply written so that they are accessible to as broad a readership as possible. Before preparing articles, authors should consult a current journal issue to make themselves familiar with the general format of the journal. A sample issue is available at https://journals.iucr.org/c/sample_issue.html.

4.2. Title and authors

The Title of the article should be written to appeal to a wide audience and should include key phrases in the subject area. The most effective titles are generally no more than 10–12 words in length. The use of acronyms or abbreviations should be avoided.

The full first name of each author is preferred. The published article may have one or more authors (correspondence authors) who are responsible for communications after publication. These authors are marked with an asterisk in the published article.

4.3. Synopsis

A one or two sentence Synopsis of the main findings of the article should be supplied along with a suitable graphic for inclusion in the contents pages.

4.4. Abstract and keywords

The Abstract should state as specifically and as quantitatively as possible the principal results obtained, and should provide an indication of the broader significance of the work. It should be capable of being understood on its own without access to the text or figures and should be suitable for reproduction by abstracting services without change in wording. It should make no reference to tables, diagrams or atom numbers contained in the article. It should not contain footnotes and should not include the use of `we' or `I'.

Authors should supply at least five carefully selected keywords. These may include synonyms and specific phrases related to the subject of the article.

4.5. Introduction

The chemical context should be outlined in an introductory paragraph that provides the background of the study and the scientific rationale for conducting the work. The origins of any compound(s) reported and their relationship to earlier research should be mentioned along with any relevant citations to related literature.

4.6. Results and discussion

The discussion may include a description of the science and the outcomes that were enabled by the study, and an analysis of how the structural observations help the understanding of a chemical, physical or structural question being investigated. Interesting and novel aspects of the reported structures can be described; this might include a description of the coordination geometry, the connectivity within an extended structure, the supramolecular or intermolecular architecture of a structure, details of any unusual features, such as disorder and twinning, or any determination of the absolute structure etc. A detailed comparison with any closely related published results is encouraged. The discussion of any structure(s) should enhance the observations with a deeper analysis. For example, a description of the dimensionality and motifs present in a hydrogen-bonding network is more informative than just stating that hydrogen bonding exists. A report that mostly describes just the metrics of a crystal structure determination without discussing the analysis in a broader scientific context may be more suitable for publication in Acta Crystallo­graphica Section E.

4.7. Experimental data

For Word submissions reporting crystal structures, a table of experimental data may be prepared using the table tools within the Word template (available from https://journals.iucr.org/services/wordstyle.html).

For CIF submissions, experimental data are extracted and tabulated automatically from the submitted results file (CIF). During tabulation, some numerical items may be formatted with a revised number of decimal places to conform to a consistent style for the journal.

The descriptions 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.

Descriptions of refinements should adequately document any non­routine procedures (e.g. twinning, disorder or excluded solvent) so that the experiments or refinement strategies can be understood.

It is recommended that authors use the latest version of refinement software whenever feasible. 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 pages at https://journals.iucr.org/c/services/authorchecklist.html). Co-editors may request any additional experimental data or material they feel necessary to complete a full review of the article.

4.8. Acknowledgements

Acknowledgement should be given for any assistance provided to the study (see Section 3.5). 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.

4.9. References

References to published work should be cited in the format detailed in Section 7.

4.10. Atomic sites

Recommendations for defining atom coordinates and atom labelling are given in the online author help pages at https://journals.iucr.org/services/cif/tips.html. See also Section 6.3.

4.11. Geometry data

For submissions reporting crystal structures, all symmetry-unique bond lengths and angles, as well as those involving H atoms, should be included in the submitted results file (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.

4.12. Geometry tables

For Word submissions reporting crystal structures, geometry tables can be created using the table tools within the Word template (available from https://journals.iucr.org/services/wordstyle.html).

For CIF submissions, 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 https://journals.iucr.org/c/services/extratables.html.

4.13. Chemical scheme

A chemical structure diagram (typical examples are shown below) should be included for crystal structure reports of all but noncovalent inorganic structures. Authors are required to submit such diagrams electronically in one of the formats listed in Section 5. 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.

Authors are also encouraged to submit chemical connectivity (MOL, CML, CHM, SMI) files of reported structures with their articles; these can often be generated by the software used to generate the scheme. These files will be made available as part of the supporting information for each article and will be used to provide InChI (International Chemical Identifier) keys for the article, making the structures easier to find in the chemical literature.

4.14. Diagrams to be included in the publication

Diagram requirements are given in Section 5. 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.

For articles reporting molecular structures, a labelled displacement ellipsoid diagram showing each symmetry-independent species is required; solvent molecules or H atoms may be omitted if desired. 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. For noncovalent inorganic structures, a packing or polyhedron diagram is required. 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 article.

Authors are welcome to supply additional diagrams, such as packing diagrams, showing extended structures or intermolecular interactions, or diagrams depicting noncrystallographic information, e.g. spectra. These diagrams can either be included in the published article or made available as part of the supporting information. 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.

An image which summarizes the message of the article, and can be used as a thumbnail on the contents pages and the first page of the article, should be provided.

4.15. Structure factors

The reflection data h, k, l, Y_meas, σY_meas, Y_calc (where Y is I, F² or F), should 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 Section 4.7).

4.16. Powder diffraction data

Authors of powder diffraction articles should consult the notes provided at https://journals.iucr.org/c/services/powder.html. For articles that present the results of powder diffraction profile fitting or refinement (Rietveld) methods, the primary diffraction data, i.e. the numerical intensity of each measured point on the profile as a function of scattering angle, should be deposited. Articles reporting Rietveld refinements should include a figure showing the diffraction profile and the difference between the measured and calculated profiles.

4.17. 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.

4.18. Absolute structure

Absolute structure is relevant in any noncentrosymmetric 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].

5.1. Size, lettering and symbols

Diagrams should be as small as possible consistent with legibility. They will normally be sized so that the greatest width including lettering is less than the width of a column in the journal (8.8 cm). Fine-scale details and lettering should be large enough to be clearly legible (ideally 1.5–3 mm in height) after the whole diagram has been reduced to one column 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.

5.2. Figure numbering and captions

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

5.3. Video and multimedia content

Multimedia content (e.g. time-lapse sequences, three-dimensional structures) is welcomed. The preferred file formats for multimedia are given at https://journals.iucr.org/services/filetypes.html.

6.1. 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'.

6.2. 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. As far as possible the crystallographic nomenclature should correspond to the systematic name. Any accepted trivial or nonsystematic name may be retained and the corresponding systematic (IUPAC) name can 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 should correspond with the enantiomeric composition and the selected configuration.

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

6.3. Crystallographic nomenclature

Authors should follow the general recommendations produced by the IUCr Commission on Crystallographic Nomenclature (see reports at https://www.iucr.org/resources/commissions/crystallographic-nomenclature/).

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 + 1/2, y − 1/2, −z + 3/2]. For the labelling of symmetry-related atoms in diagrams, see Section 5.1.

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].

A symbol such as 123 or hkl without brackets is understood to be a reflection, (123) or (hkl) a plane or set of planes, [123] or [uvw] a direction, {hkl} a form and 〈uvw〉 all crystallographically equivalent directions of the type [uvw]. Other bracket notations should be explicitly defined.

9.1. Author tools

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

(a) Word templates are available from https://journals.iucr.org/services/wordstyle.html.

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

(c) For CIF submissions, articles can be edited using publCIF, available from https://publcif.iucr.org.

(d) For CIF submissions, a preview of an article may be printed using the printCIF service at https://publcif.iucr.org/services/tools/printcif.php.

9.2. Status information

Authors may obtain information about the current status of their article at https://journals.iucr.org/services/status.html.

9.3. Proofs

Proofs will be provided electronically in portable document format (pdf). The submitting author will be notified by e-mail when the proofs are ready for downloading.

9.4. Reprints

After publication, the submitting author will be able to download the electronic reprint of the published article, free of charge.

9.5. Publication and social media

Section C is available online at https://journals.iucr.org/c. Once your article has been published it will also appear on Twitter @ActaCrystC.

9.6. Open-access articles

The final published version of each open-access article is deposited with PubMed Central on behalf of the authors.

9.7. Publicising your article

There are many ways in which the IUCr promotes and raises awareness of articles published in its journals. More information on this and suggestions on how to publicize your articles can be found at https://journals.iucr.org/c/services/articlepublicity.html.