Notes for authors

Acta Crystallographica Section C: Structural Chemistry is the journal of choice for publishing any science to which structure contributes a role, with a particular focus on the field of structural chemistry. As well as research papers, the journal publishes lead articles, feature articles, letters to the editor and scientific comments. The journal specializes in the rapid publication of articles that highlight interesting research enabled by the determination, calculation or analysis of small-molecule crystal and molecular structures in the chemical sciences; articles are not limited to just reports of crystal structures. The journal has a reputation for publishing high-quality crystal structures, but articles describing difficult or challenging structures and the strategies used to handle them are also welcomed.

1. Categories of submission

Contributions should conform to the general editorial style of the journal. Acta Crystallographica Section C: Structural Chemistry pub­lishes the following categories of articles, all of which are peer reviewed.

1.1. 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.

1.2. 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 Editor. The Section Editor will discuss the treatment of the topic, the length of the article and the delivery date of the manuscript with invited author(s).

1.3. 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.

1.4. Scientific Comment

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

1.5. 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 Editor.

1.6. 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 Editor.

2. Submission requirements

2.1. Article preparation

Guidelines for the preparation and editing of an article are available from the online author help page at //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 //journals.iucr.org/services/wordstyle.html , where full instructions are given.

For CIF submissions, a free editor, publCIF, may be obtained from //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 //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 page at //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 //journals.iucr.org/services/cif/printcif.html or by using publCIF.

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

2.2. Method of submission

Full details of the submission procedure can be found at //journals.iucr.org/c/services/submitinstructions.html. Articles should be sub­mitted at //journals.iucr.org/c/services/submit.html or via the online publCIF interface.

During the submission procedure, authors will be required to submit additional electronic files; these include the chemical scheme (see §3.12), diagrams to be included in the publication (see §3.13) and structure factors (see §3.14) or powder diffraction data (see §3.15).

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.

2.3. Handling of articles

Each article is handled by an 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 //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. Further information on the peer-review process can be found at //journals.iucr.org/c/services/peerreview.html .

If, after review, no revisions are necessary, the article will be accepted and prepared for immediate electronic publication. If the review reveals that revisions are required, the submitting author will be contacted directly and asked to revise the article (see §2.4).

Once an article is accepted, it is the responsibility of the Managing Editor to prepare the 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 article will be the date on which the Managing Editor receives the last item needed. The Section Editor reviews all accepted articles and reserves the right to request or make appropriate changes to ensure conformity with Section C standards; in the unlikely event of significant changes being required at this stage, the authors will be contacted promptly.

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 manuscript is not acceptable after two revision cycles, it will not be considered further. An article that has been rejected must not be resubmitted to any IUCr journal unless the reasons given for the rejection have been fully addressed in the revised version.

2.5. Author's warranty

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 manuscript 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 inclusion of material in an informal publication, e.g. a preprint server or a newsletter, does not preclude publication in an IUCr journal.

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 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. 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 //journals.iucr.org/services/languageservices.html .

2.7. Author grievance procedure

An author who believes that an article has been unjustifiably treated by the Co-editor may appeal initially to the Section Editor for a new review and, finally, to the Editor-in-chief of IUCr journals if the author is still aggrieved by the decision. The initial appeal must be made within 3 months of rejection of the article. The decision of the Editor-in-chief is final.

2.8. Copyright

Except as required otherwise by national laws, an author will be required to agree to the transfer of copyright before a manuscript can be accepted. Authors selecting open-access publication do not need to transfer copyright. Details of author rights can be found at //journals.iucr.org/services/authorrights.html .

2.9. Open access

Authors are given the opportunity to make their articles `open access ' on Crystallography Journals Online . 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 //journals.iucr.org/services/openaccess.html .

2.10. Publication fees

There are no fees for colour figures or electronic reprints. If authors require open access or printed reprints there is a charge and details will be given at the proof stage.

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 at //journals.iucr.org/c/services/cifinfo.html .

3.1. Title and authors

The Title should be short and informative.

The full first name of each author is preferred. 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 article.

3.2. 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 Table of Contents.

3.3. 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 each studied compound should be given here if it is not included in the Title. Authors should also supply at least five keywords.

3.4. 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.

3.5. 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.

3.6. 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 //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 page at //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.

3.7. Acknowledgements

Acknowledgement should be given for any assistance provided to the study (see §2.5). 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.

3.8. References

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

3.9. Atomic sites

Recommendations for defining atom coordinates and atom labelling are given in the online author help page at //journals.iucr.org/services/cif/tips.html . See also §5.3.

3.10. 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 from Crystallography Journals Online (see §8.7).

3.11. Geometry tables

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

3.12. Chemical scheme

A chemical structure diagram (typical examples are shown below) must 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 §4. 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.

3.13. Diagrams to be included in the publication

Diagram requirements are given in §4. 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 paper 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.

3.14. Structure factors

The reflection data h, k, l, Y_meas, σY_meas, Y_calc (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 §3.6).

3.15. Powder diffraction data

Authors of powder diffraction articles should consult the notes provided at //journals.iucr.org/services/cif/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.

3.16. 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.

3.17. 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 //journals.iucr.org/c/services/help/artwork/guide.html . Figures and chem­ical structure schemes (see §3.12 for typical examples) 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).

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 the width of a column in the journal (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 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.

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. For details of how to prepare enhanced three-dimensional figures, see §4.4.

4.4. Interactive online figures

An online tool for authors to prepare standard and corresponding three-dimensional interactive structural diagrams is available from https://submission.iucr.org/jtkt .

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 (https://www.chemaxon.com/products/marvin ) and ACD/ChemSketch (https://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 https://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 + , y − , −z + ]. For the labelling of symmetry-related atoms in diagrams, see §4.1.

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 ].

6. References

The publCIF editor (see §2.1) 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 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 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. (2014). 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.

Ferguson, G., Schwan, A. L., Kalin, M. L. & Snelgrove, J. L. (1997). Acta Cryst. C53, IUC9700009.

International Union of Crystallography (2012). (IUCr) Structure Reports Online, //journals.iucr.org/.

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

Satomura, T., Sakuraba, H., Hara, Y. & Ohshima, T. (2014). Acta Cryst. F70, 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). Private communication (refcode: PYMTLI01). CCDC, Cambridge, England.

Yariv, J. (1983). Personal communication.

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

7. Supporting information

7.1. Purpose and scope

Supporting information (such as experimental data, additional figures and multimedia content) that may be of use or interest to some readers but does not form part of the article itself will be made available from the IUCr archive. Arrangements have also been made for such information to be deposited, where appropriate, with other relevant databases.

7.2. IUCr archive

All material for deposition in the IUCr archive should be supplied in one of the formats described at //journals.iucr.org/services/filetypes.html . Structural information (for small-molecule structures) should be supplied in CIF format.

8. Author information and services

Full details of guidelines for the preparation and editing of an article, 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 //journals.iucr.org/c/services/cifinfo.html .

8.1. Author tools

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

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

(b) The checkCIF/PLATON service at //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 //publcif.iucr.org .

(d) A toolkit for preparing enhanced figures is available at https://submission.iucr.org/jtkt .

(e) For CIF submissions, a preview of an article may be printed using the printCIF service at //journals.iucr.org/services/cif/printcif.html .

8.2. Status information

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

8.3. 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).

8.4. Reprints

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

8.5. Open-access articles

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

8.6. 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 //journals.iucr.org/c/services/articlepublicity.html .

8.7. Crystallography Journals Online

All IUCr journals are available on the web via Crystallography Journals Online at //journals.iucr.org/.