FAQs
Electron Diffraction Data in the CSD
Solution
Electron diffraction data is included in the CSD and this FAQ details how to find and deposit electron diffraction data as well as the criteria for inclusion. For more information about what data can be deposited into the CSD see our Deposit A Structure page.
The number of structures in the CSD measured using electron diffraction techniques is increasing; at the beginning of 2020 there were approximately 50 structures in the CSD measured with electron diffraction. As part of a CSD Improvement Project, we are working to ensure these structures are labelled consistently and can be searched for using CCDC tools.
To ensure structures can be reliably located, CSD entries that were identified as being measured with electron diffraction techniques should be flagged with the phrase ‘electron diffraction’. This information is added to the entry during Data Curation. Our curation software checks information in certain CIF fields to automatically identify electron diffraction studies, but this information can also be added manually (if one of our Scientific Editors identifies an electron structure during the curation process).
We are working to improve our tools to automatically identify and label more of these structures by recognising them from the information provided to us upon deposition of the structure to the CSD.
How to find structures:
Electron diffraction studies can be found using CCDC ConQuest. Select the ‘All Text’ button in the ‘Build Queries’ tab and then type ‘electron diffraction’ in the box which appears. This should return a list of results where the keyword ‘electron diffraction’ is associated with the entry.
There may be more information about the refinement process in the CCDC Notes section, found in the ‘Experimental’ Tab. This may include the type of electron diffraction collection method, if it is clear in the article. The level of detail varies in entries in the CSD. This information is also displayed in our WebCSD system in the ‘Remark’ field.
Image of Refcode DOBCAB showing how electron diffraction structures are displayed in WebCSD
Some of the structures identified are from a combination of techniques, e.g. using electron diffraction data to obtain a structural solution and powder X-ray diffraction data for the structural refinement. These structures and cases in which the paper mentions an electron diffraction study and we do not have the corresponding electron diffraction data in the CSD are labelled with the phrase ‘electron-diffraction’. This is so they will not appear in searches for ‘electron diffraction’ but remain findable. We are in the process of updating our labelling procedures.
How to deposit:
To ensure your structure is correctly identified as being measured with electron diffraction techniques we encourage you to document this within your CIF file, by including ‘electron’ in the _diffrn_radiation_probe field, e.g.:
_diffrn_radiation_probe electron
We also suggest including information about the data collection in the following CIF fields:
| CIF field | Information to include |
| _diffrn_measurement_method | The method used to measure the data e.g. ‘Rotation Electron Diffraction’ |
| _diffrn_radiation_type | ‘Electron’ |
| _diffrn_source | The general electron source used in experiment e.g. ‘electron microscope’ |
| _diffrn_source_type | Specific information about the electron source used, such as make/model or name of the equipment |
| _diffrn_measurement_device | The general name of the equipment used to collect the diffraction data |
| _diffrn_measurement_device_type | Specific make/model of the equipment used e.g. ‘FEI Tecnai F30ST’ |
| _diffrn_detector | The general name of the detector used |
| _diffrn_detector_type | Specific make/model of the detector used |
| _exptl_special_details | Any additional special details about the experimental setup |
| _diffrn_special_details | Any additional special details about the diffraction data collection |
The CCDC has a list of guidelines of the information that we recommend to be present in a CIF, which can be found here.
The current CCDC policy is that we will add electron data into the CSD if atom positions are provided, and the structure is the result of a least-squares refinement (e.g. has an R factor). Other electron data (without atom positions or that has not been refined) will still be stored as a non-CSD structure. These structures will be available from WebCSD/Access Structures – but will not appear in the CSD. For more information about non-CSD structures, please read this FAQ.
What next?
We are currently working to evolve our underlying database and associated systems and so we hope to be able to enhance our deposition processes and provide more options for you to recognise this type of structure and filter on these structures in the future.
Important information:
This is an ongoing improvement project at CCDC. As such, until the 2021 version of the database is released (estimated November 2020), a small proportion of the electron diffraction studies in the CSD may be incorrectly labelled. If you require a list of the identified electron structures in CSD before this release, please write to CCDC (data_edits@ccdc.cam.ac.uk) and we will provide one.