Department of Chemistry

Administration

The X-ray Laboratory Administration site. These files contain information for the administration of the X-ray Laboratory.

Acknowledgement.

If you use the data collected at the X-ray diffraction laboratory, please use this acknowledgment in your publications. Thank-you.

The X-ray diffractometers and crystallographic computing systems in the X-ray Diffraction Laboratory at the Department of Chemistry, Texas A & M University were purchased with funds provided by the National Science Foundation (CHE-9807975, CHE-0079822 and CHE-0215838).  The Bruker Venture, Quest and ECO diffractometers were purchased with funds provided by Texas A and M University Vice President of Research.

 

Standard experimental paragraph for X-ray Powder Diffraction.

The sample was placed in the sample holder of a two circle goniometer, enclosed in a radiation safety enclosure.  The X-ray source was a 2.2kW Cu X-ray tube, maintained at an operating current of 40 kV and 25 mA.  The X-ray optics was the standard Bragg-Brentano para-focusing mode with the X-ray diverging from a DS slit (1mm) at the tube to strike the sample and then converging at a position sensitive X-ray Detector (Lynx-Eye, Bruker-AXS).  The two-circle 250mm diameter goniometer was computer controlled with independent stepper motors and optical encoders for the theta and 2theta circles with the smallest angular step size of 0.0001 degrees 2theta.  The software suit for data collection and evaluation is windows based. Data collection is automated COMMANDER program by employing a DQL file. Data is analyzed by the program EVA.

 

 

 

 

X-ray Diffraction Laboratory Policy and Procedures

April 7 2021

Use of Single-crystal X-ray Diffraction Instrumentation.

These rules have been approved by the X-ray Users Committee and apply to all single-crystal X-ray Diffraction Instruments.            

Rule 1:

Users must reserve time through the Calendar Reservation system.

The calendar reservation will be limited to 7 days for the APEXII diffractometer (APEX22, room 2409), the Venture and the Quest diffractometers.  

 

Rule 2:

If you do not start using the instrument before 10:00 am on the day of your reservation, the instrument becomes open and available on a first-come-first-serve basis.  This rule will always apply unless users are notified in writing that the operator will be late for some reason.

 

Rule 3:

After your data collection finishes, you have 60 minutes from the time corresponding to the last frame collected to: (1) perform other minor measurements such as face indexing and crystal dimension determination; (2) to start working on a new crystal if you have reserved the instrument on that day. After 60 minutes, your crystal can be removed and the instrument becomes open and available on a first-come-first-serve basis. You are encouraged to measure and face index your crystal before collecting the data.  If you want to start a new experiment and need more than 60 minutes, you are required to leave a note on the keyboard of the instrument. This note should indicate the time, your name, and the amount of time (an extra 90 minutes maximum) that you need before starting your new experiment.

 

Rule 4:

After your indexing finishes, you have 60 minutes from the time corresponding to the last frame collected to start your data collection. After 60 minutes, your crystal can be removed and the instrument becomes open and available on a first-come-first-serve basis. You are encouraged to measure and face index your crystal before collecting the data. If you want to start a new experiment and need more than 60 minutes, you are required to leave a note on the keyboard of the instrument. This note should indicate the time, your name, and the amount of time (an extra 90 minutes maximum) that you need before starting your new experiment.

 

Rule 5:

If you have reserved a day and are unable to use the instrument, you are required to send an email to the user listserv (all_xray) indicating that the instrument is vacant. At this point, the instrument becomes open and available on a first-come-first-serve basis.

 

Rule 6:

Rule 6.1: When a data collection overruns the allotted reserved time on an instrument, the user who started the data collections must leave a note on the keyboard with their 24/7 telephone contact (email + phone) and contact the next user whose time will be affected.  Please consult the Calendar Reservation to find out who the next user is.

 

Rule 6.2: If a note is present on the keyboard, no user will stop a data collection unless instructed to do so by the person who started the data collection or by the facility manager.

 

Rule 6.3: In the absence of a note left on the keyboard, the facility manager will have the option of stopping the data collection and make the machine available for the next user. If the facility manager is not present in the facility, the user who reserved the instrument will have the option of stopping the data collection if a note was not left on the instrument.

 

Rule 7:

No user will reserve two consecutive days on the APEXII CCD Diffractometers