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General info:

Users of X-ray diffractometers (powder XRD and SAXS) may request access to the X-ray lab and permission to work on x-ray equipment. This however reqiers to pass Radiation Safety traning and then training on specific instrument.

There are two levels of the lab access: 
  - Supervised (Individual) user is allowed to work on the instrument only under the supervision of XCC staff, an unsupervised user or the crystallographer (PI).
  - Unsupervised (Authorized) user is one who can access lab anytime and is allowed work on the instrument independently.

You should consider to get trained on the XRD instrument if you planning to use machine often as training takes a bit of time and is costly. If you need to use XRD only occasionally, you can submit samples and XCC stuff with perform experiment and basic analysis. In this case you will be referred as Submitting user.
Our Rates (updated 1/1/21).

How to become an XCC User:

• In order to operate X-ray systems, you have to be trained but first you should pass "Radiation Safety Training for Use of X-ray Devices" online (start here) and, on completion, request radiation safety certificate; for more see Radiation safety office website.
  
  
• To start training on the specific instrument: you should provide XCC with an electronic copy of the radiation safety certificate and filled out and signed by the advisor User Registration Form.
  

• For each training you should bring 2-3 samples and a filled out Sample Submission Form. After successful completion of the final training you will be given login to the online scheduling system (FACES) and card access to the lab.

  NOTE that there is a different SAXS submission form for submitting samples and training on SAXS instrument.
  

• On the completion of training you will become supervised user working under supervision of XCC staff, TA or any unsupervised user during normal working hours.

   

  After 2-3 weeks of experience (the length depends on how many samples and how often you run), you may apply for unsupervised user status to be able to work independently with full access anytime. This status is granted by the radiation safety office (RSO). To get this status please send a signed "Training and Experience" (T&E) form to the PI (pzavalij@umd.edu) who will sign an forward it to RSO. Note: RSO approval takes time so please be patient.

   

  Feel free to stop by if you want to discuss measurements or training. My office is next to XCC lab in the basement of wing 1 in the Chemistry building, office hours 1pm – 5pm, email: pzavalij@umd.edu, phone: 5-1861.

   

Submiting Samples for Analysis:

• Single Crystals for Crystal Structure Determiantion has to be submitted to the X-ray lab along with Single Crystal Sample Submission Form for Smart Apex2, D8Venture & Laue instruments.
  
  

• Powder Diffraction (XRD) samples have to be submitted along with Powder Sample Submission Form for D8Advance, C2/D8Discover, X'pertPro instruments.
  
  

• SAXS samples have to be submitted along with SAXS submision Form (Word).
   

• In cases when sample has to be stored under certain conditions, only the form may be submitted and the user will be asked to bring the sample when experiment is scheduled  

   

• First time users must have the sample submission form signed by advisor and are strongly encouraged to discuss experiemnt with XCC staff first, expecially SAXS samples.

• Internal users have to drop off samples atusers have to drop off samples at the XCC lab. DO NOT mail samples by internal mail

• External users may send sample by mail along with corresponding Sample Submission Forms. Note that regular mail takes too long so we suggest to use expedite services FedEx, UPS or alike.
   
   

Managing Data Files and Folders:

Data Folders:

• ALL FILES (raw experimental and reduced data) should be placed only in the directory "C:\<DataDirectory>\<PI>*", where <PI> is name assigned for each group (usually <PI> is Advisor last name or last name & initials, <DataDirectory> is a directory name where all data are stored and is specific for each instrument).

• It is advised that each user creates his/her own subdirectory <UserName> in the <PI> directory, especially when there are several users from the same group/advisor.

• It is also strongly recommended to create sub-subdirectory for each project (set of samples). When another project is stored in the same directory, it will be impossible to use original raw data from the first project as the instrumental parameter file will be overwritten with newer one that could be different.

• Please to not make copies of experiemntal files or folders on the instrument computer as all data are almost instrantly synchronized and it creates mess if there are multiple cop[ies of the same data. Yet you are welcome to make as many copies as you want on external disks and memory sticks.

• Sub-directory name could be for example <date+project-name, so that full path looks like:
  - On D8 Advance  - C:\_Data\<PI>\<UserName>\<Date-Project>\
  - On C2 Discover  - C:\FRAMES\<PI>\<UserName>\<Date-Project>\
  - On PANalytical  - C:\XRD data\<PI>\<UserName>\<Date-Project>\
  - LAUE system     - D:\_UserData\<PI>\<UserName>\<Date-Project>\

• SAXS data files are stored on Linux box in subdirectory inside directory external, for example:
  - Xeuss Linux PC - \\...\external\YYYY-MM-DD_Adisor-UserName\
  Details on how to create and organize files are provided during training an can be found in log book.
   

 Storing data files:

• Data folders and files are automatically archived/backed-up to server PC almost instantly. On a daily basis data is copied to external disk and less often (weekly and monthly) to external clouds and the university server.

• Nevertheless it is strongly recommended to users to make their own copy of data.

• All data is stored on the instrument computers for at least for 3 year. Then they may be archived and deleted in case of large raw data files, e.g. *.gfrm frames on C2. Yet all data is stored indefinitely on external hard drives and the university server and can be requested anytime.
   

Results sent to Users, Final Reports & Data Retrieval :

Powder Data are provided to users (who has no access to the lab):

• Text file (.xy) with powder diffraction pattern containing two columns: 2-theta and Intensity that can be imported in any spreadsheet or XRD software.

• Power Point slide(s) with diffraction pattern and (if performed) with identified phases and their approximate quantities.

• Sample image, copy of original experimental data (frames), powder diffraction pattern in other formats available on request.
   

Single Crystal data are usually provided in ready for publication form:

• The final results are always checked for chemical sense and consistency. Nevertheless it is strongly recommended that user double check geometry, charge balance, compare similar distances, angles, and especially amount of H atoms and their position, and H-bonds.

• In non-trivial cases, during the crystal structure determination/refinement user could be asked about additional information or supplied with preliminary structure for checking or in order to resolve problems/questions that arise and to determine necessity of finalizing the structure if it is not what was expected.

• If a specific labeling scheme is desired, please provide it in the crystal submission form.

Final structure is checked using Check-CIF procedure from Platon software (or online from IUCr site) and the final results are supplied in the following files named by 4-digit lab crystal number:

• Crystallographic Information File (.CIF) containing a variety of crystallographic and experimental information. Planes and dihedral angles between them are refined per request and added in the CIF file in _geom_special_details section.

• In case of substantial disorder often included is also cif file *DRAW.CIF (or *ORDERD.CIF) with removed alternative orientation of disordered species.

• Final report file (.HTML) containing 5 to 8 tables with crystal data, experimental conditions, atomic parameters, bond length, valence and torsion angles, occupation factors and H-bonds. Description of crystal, experimental setup and brief refinement details are also included. The final report usually includes an ellipsoid plot (unlabeled) and sometimes packing diagram.

• ShelX coordinate file (.RES) and final refinement output file (LST) are provided if requested. These files contain information which can be used to evaluate quality of the refinement and experimental data, e.g. largest peaks and holes from the residual difference Fourier map.

• Note: now ShelXL software embeds .RES and .hkl files inside .CIF and therefore they are usually not provided separately.

• Platon output files (.lis) with various geometric calculations and Check-CIF warning are generated and sent only when requested.

• Full final data set contains much more files including original files from the integration, crystal snapshots, structure drawing (usually included in the final report), and all refinement files. These data are compressed in ####.zip file and can be furnished per request.