Department of Chemistry & Biochemistry, University of Maryland, College Park, MD 20742

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Sample Submission

Single Crystal sample has to be submitted to the X-ray lab along with Single Crystal Sample Submission Form which has to be signed by PI/advisor.  In cases when sample has to be stored under certain conditions, only form can be submitted and the user will be asked to bring the sample when experiment is scheduled.

Single Crystal submission form: PDF or Word.

Powder experiments have to be scheduled (by all users) using sign-up sheets. Users who do not perform experiment on their own have to submit sample along with Powder Sample Submission Form to the PI or an authorized user (see below).

Powder Sample submission form: PDF or Word.

External users may send sample by mail along with Single Crystal Sample Submission and Payment Form or Powder Sample Submission Forms. The form can be submitted either with sample or by fax (301)314-9121.


 

     

Powder Diffractometer User Guide

Short guide can be downloaded here. (Complete guide will be provided online when ready)

   

Managing Data on the Powder Diffractometer:

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

◦ ASCII file with powder diffraction pattern containing two columns: 2-theta and Intensity that can be imported in any spreadsheet.

◦ Power Point file with diffraction pattern and (if performed) with identified phases.

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

Handling data:

ALL FILES (raw experimental and reduced data) should be placed only in the directory "C:\FRAMES\<PI>*", where <PI> is name assigned for each group (usually PI/Advisor last name).

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. The latter simplifies archiving data  and removing large arrays of raw data (frames) from the computer.

It is also strongly recommended to create sub-subdirectory for each project (set of samples), which can be for example date, so that full path will look like:
C:\FRAMES\<PI>\<UserName>\<Project>\
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 never one which may be different.

Storing data:

The lab does not archive/back-up data on regular basis. It is done only for purposes of accidental system failure.
Therefore:

1) It is solely responsibility of the users to make copy of their own data.

2) Large raw data (frames) stored in *.gfrm files have to be remove when not needed or after backup copy is made.

3) NOTE: Raw data files (*.gfrm) older than 6 month will be removed w/o warning in order to maintain reasonable disk space available. However other files might be stored as long as needed until users are affiliated with the university.

   

Single Crystal data: Final Reports & Data Retrieval

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, compare similar distances, angles, and especially amount of H atoms and their position, as well as H-bonds.

 

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

The final structure is checked using Check-CIF procedure (recommended by IUCr) and the final results are supplied in the following files named by 4-digit lab crystal number:

 

Crystallographic Information File (CIF) containing variety of crystallographic and experimental information. Planes and angles between them are usually refined for rings and added in CIF file in _geom_special_details section

 

Final report as word file containing 5 to 8 tables with crystal data, experimental conditions, atomic parameters, bond length, valence and torsion angles, occupation factors and H-bonds. Short comments and quality level (if not obvious) is usually included. The final repost includes XSHELL ellipsoid plot (usually unlabeled) and sometimes packing diagram

 

ShelX: original coordinate file (RES) and final refinement output file (LST). 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.

 

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Reflection data as FCF file containing list of unique observed reflections and their observed and calculated intensities. This file is required by some journal as supporting materials. This file is e-mailed on the user request.

 

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Platon output files (.lis) with various geometric calculation and Check-CIF warning. This file is e-mailed on the user request.

Full 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. 

 

All files are placed on the FTP server (128.8.178.98) in subdirectory UM#### within the PI/Advisor directory.

 

Users may request U-Serv account if they do not have one. Currently the ftp server is being updated and will be available soon.

 

In addition full data including frames are archived on CD or DVD disks and recently on the external hard drive. Copy of the data available on request.

 

There is ongoing project to provide web-based access to all data as well as to create searchable interface.