international union of crystallography\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

ISSN: 2056-9890

Notes for authors

Keywords: Notes for authors.

Acta Crystallographica Section E: Structure Reports Online is the IUCr's open-access structural communications journal. It provides a fast, simple and easily accessible publication mechanism for crystal structure determinations of inorganic, metal-organic and organic compounds with validated structures. The electronic submission, refereeing and publication facilities of the journal ensure rapid and high-quality publication of fully validated structures. The journal encourages reports of routine as well as interesting and difficult structures. Two article types are published. Research Communications are longer articles describing one or more structure determinations with appropriate discussion of the science. Data Reports are extended abstracts reporting individual structure determinations with comments on the chemical significance of the structure.

1. Categories of submission

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

1.1. Research Communications

Research Communications describe one or more structure determinations and give the scientific context of the study. Research Communications should not normally exceed six journal pages (6000 words). A discussion on the immediate and wider significance of the results is encouraged.

1.2. Data Reports

Data Reports are extended abstracts, one page in length, each describing the structure of a single inorganic, metal-organic or organic compound.

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 . All articles must be submitted in Crystallographic Information File (CIF) format. A free CIF editor for authors, publCIF, may be obtained from . An online version of publCIF is also available.

Authors are required to validate their CIF and structure factors using the checkCIF service at . 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 , 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 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 . Articles should be submitted at or via the online publCIF interface. Authors will be asked whether their submission is to the Research Communications or Data Reports section.

During the submission procedure, authors will be required to submit additional electronic files; these include the chemical scheme (see §3.3.4[link]), diagrams to be included in the publication (see §3.3.5[link]) and structure factors (see §3.3.6[link]) or powder diffraction data (see §3.3.7[link]). Authors will also be asked to agree to an open-access licence (see §2.8[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 §8.5[link]).

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. hb3127), and should be used in all subsequent communications with the Editorial Office and Co-editor.

2.3. Handling of articles

All contributions will be seen by the Main Editors before peer review. The Main Editors will decide whether articles are considered for the Research Communications or Data Reports sections, or are rejected without further review.

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 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 Main Editors review all accepted articles and reserve the right to request or make appropriate changes to ensure conformity with Section E 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 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 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 . 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 .

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 Main Editors 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

Authors will not be asked to transfer copyright to the IUCr, but will instead be asked to agree during article 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 .

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. Research Communications

Research Communications describe a series of related structure determinations or an individual structure and should report results that are of scientific value. Authors are encouraged to report and discuss more than one structure rather than publishing a series of single-structure articles. Research Communications should normally include the following text sections: Abstract, Chemical context, Structural commentary, Supramolecular features, Database survey (optional), Synthesis and crystallization, Refinement. In addition, at least one figure per structure will be published, an ellipsoid plot being required for each molecular species and a polyhedral plot for each inorganic structure. A packing diagram should be supplied if there are interesting features. A chemical scheme is also required for metal-organic and organic structures. Authors are encouraged to include any relevant data files or extra figures in the supporting information for their article, which will also include data derived from the CIF.

3.1.1. Title and authors

The Title should be short and informative, e.g. `Crystal structures of …'. 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.

3.1.2. 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 three keywords.

3.1.3. Chemical context

The chemical context should be outlined in at least two informative introductory sentences that provide the background to the current study, the origins of the compound(s) reported and the relationship to earlier research. Authors should provide any relevant citations to related literature. Further discussion emphasizing the scientific focus of the work or any other relevant results concerning the presented compound(s) could be included, such as results from other chemical or physical techniques.

3.1.4. Structural commentary

Interesting or unusual aspects of the molecular structure and/or the extended connectivity should be described. This might include coordination geometry, molecular geometry, modes of association, conformation, configuration, contents of the asymmetric unit, any crystallographic symmetry, disorder, etc. For an extended or polynuclear structure, the description should allow the reader to readily understand the connectivity.

3.1.5. Supramolecular features

Any significant supramolecular features, and interesting or unusual aspects of the extended connectivity such as modes of association, aspects of the crystal packing, intermolecular interactions and hydrogen bonding, etc., should be discussed. A discussion of hydrogen bonding should describe the motifs and networks generated. A useful commentary on hydrogen bonds is available from the online author help page (see §7[link]).

3.1.6. Database survey (optional)

Authors are strongly encouraged to carry out a search of the relevant database for comparable structures and provide a commentary and analysis of the geometry in terms of a comparison with literature ranges.

3.1.7. Synthesis and crystallization

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.

3.1.8. Refinement

The description of the refinement should adequately document any non-routine procedures (e.g. twinning, disorder or excluded solvent, specific details of any restraints or constraints) so that the experiments or refinement strategies can be understood.

3.1.9. 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.

3.1.10. References

References to published work must be cited in the format detailed in §6[link]. Excessive self-citation is discouraged.

3.2. Data Reports

Data Reports are extended abstracts each describing the structure of a single inorganic, metal-organic or organic compound. The maximum length is one page. The Abstract is the main source of information while the Related literature section provides the context to the study. Essential references (e.g. to the origin of the material studied, related structural studies, and to information supporting the reported structure) should be cited in this section, with appropriate very brief explanatory text, for example `The synthesis of the complex is described by Jones (2001). The anhydrous complex has essentially the same coordination geometry (Smith, 2003).' In addition, all references included in the supporting information, but not elsewhere in the published article, should be given here. The number of references should not normally exceed 15.

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. The figures are published in the supporting information, along with data derived from the CIF.

3.3. Other considerations

3.3.1. Atomic sites

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

3.3.2. Experimental data

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.

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 SHELXL2014/3. 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 ). Co-editors may request any additional experimental data or material they feel necessary to complete a full review of the article.

3.3.3. Geometry data and tables

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[link]).

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 .

3.3.4. 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 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 supplementary materials 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.

3.3.5. 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 article.

Authors are welcome to supply additional diagrams, such as packing diagrams, showing extended structures or intermolecular interactions or diagrams depicting non-crystallographic information, e.g. spectra. For Research Communications, these diagrams can either be included in the published paper or made available as part of the supporting information. All figures for Data Reports are published in 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.

3.3.6. 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 §3.3.2[link]).

3.3.7. Powder diffraction data

Authors of powder diffraction articles should consult the notes provided at . 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.

3.3.8. 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.

3.3.9. 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 . Figures and chem­ical structure schemes (see §3.3.4[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 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.

3.4. 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[link].

4.4. Interactive online figures

An online tool for authors to prepare standard and corresponding three-dimensional interactive structural diagrams is available from .

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/products/marvin ) and ACD/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

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 \over 2], y − [1 \over 2], −z + [3 \over 2]]. 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 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. (2015). 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,

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

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.

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 . 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 .

8.1. Author tools

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

(a) The checkCIF/PLATON service at allows CIFs and structure factors to be checked.

(b) Articles can be edited using publCIF, available from .

(c) A toolkit for preparing enhanced figures is available at .

(d) A preview of an article may be printed using the printCIF service at .

8.2. Status information

Authors may obtain information about the current status of their article at .

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[link]).

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

Acta Crystallographica Section E is an open-access journal. The costs of peer review, of journal 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 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 an article to the journal.

Authors whose institution has a full subscription to Acta Crystallographica Section C are eligible for a discount on the open-access fee. In addition, discounts are available for advance payment of open-access fees.

Full details of the open-access arrangements for Section E are available at .

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 publicise your articles can be found at .

8.7. Crystallography Journals Online

All IUCr journals are available on the web via Crystallography Journals Online at

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