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Beamline 11-BM is a dedicated high-resolution powder diffractometer at the APS. It offers high resolution powder diffraction data (< 1.2 x 10-4 Δd/d) over moderate time scales (10 minutes – 1 hour). Beamline 11-BM offers both on-site and mail-in modes of access. On-site experiments allow for a wide variety of sample environments, including variable temperature (5 K – 1800 C), electrochemical cells, and gas flow and loading.

Data Formats

To better serve a diverse user community, 11-BM mail-in data is available in different formats. Users may select the format(s) most appropriate for their analysis needs. A description of these different formats is given below.

During an 11-BM scan individual patterns from the sample are collected simultaneously on all 12 detectors. These data are later merged into a pseudo-single pattern. Data consisting of a single merged pattern are appropriate for nearly all 11-BM users.

Corrections are applied to the data when it is merged. The corrections are necessary to merge the data from the 12 separate detectors, and correct for small offset variations, differences in sensitivity, and minor fluctuations in wavelength (typically ~ 0.003%). The correction values are determined by a Rietveld refinement performed regularly on scans of a mixture of NIST standard reference materials, Si (SRM 640c) and Al2O3 (SRM 676), where the Si lattice constant determines the wavelength for each detector.

The pattern intensity and uncertainties (e.g. error or esd) are corrected to account for the number of contributing detectors at each 2θ value. The final merged single pattern has a 2θ offset of exactly zero degrees, and a single wavelength value that is provided with the dataset. Users may request the calibration data set used for their samples be sent by contacting beamline staff; please reference the name of the calibration file (e.g. aug09/11bmb_0311.calib)

Still having trouble with data formats? The 11-BM FAQ page answers a few common questions, or contact us: 11-BM staff may be able to help.

Merged Data Formats

GSAS data (.fxye)

GSAS supports many formats for powder diffraction data input. The .fxye format for GSAS has an intial header line followed by a variable number of comment lines (prefixed by a # character), then an addtional header line. The data are listed next in three columns: 1st column is 2θ position (in centidegrees, i.e. degrees × 100), 2nd is intensity, and 3rd is standard uncertainty for the intensity values (esd). This format may not be supported by all software that claims to read GSAS input files (see GSAS .raw format below)

This format is supported by recent versions of GSAS+EXPGUI and other Rietveld software including recent versions of Jana2006. The freely distributed powder diffraction data utility CMPR will also read .fxye files. CMPR can be used to display and index the diffraction data (just a few its many features) as well as export to alternative ASCII data formats.

Note for JADE users: although recent verions of Jade do appear to open .fxye files, we have heard reports that it may truncate significant digits in the intensity and ESD value columns. The pdCIF format (see below) is a better choice for Jade users.

When GSAS format files (.fxye or .raw) are requested from the web site, the appropriate GSAS instrument parameter file (.prm) is generated and included.


GSAS data (.raw)

GSAS also supports a second common format. In this format, the angular range of the data and the step size are indicated in a header and the intensities and their uncertainties (esd) are alternated with five pair of numbers per line (8 characters per number), as described in the GSAS manual.

Several different file extensions, including .gsa, .gsas, .raw, or .gs are used by different programs for this type of file. These various file extensions occasionally cause some software confusion. Feel free to rename your file extension as required for a given software package.

When GSAS format files (.fxye or .raw) are requested from the web site, the appropriate GSAS instrument parameter file (.prm) is generated and included.


TOPAS data (.xye)

The TOPAS .xye file is similar to the three column GSAS .fxye format, except 2θ position angles are expressed in degrees, not centidegrees. Topas will ignore the file header information which is bracketed between the characters "/*" and "*/", and prefixed by a "#" character.


pdCIF data (.cif)

The Crystallographic Information File (CIF) is a standard format developed by the IUCr for communication of diffraction data and results. The pdCIF format defines data names that allow CIF to be used for powder diffraction data. A number of programs, including JADE, EXPGUI, CMPR, FOX and pdCIFplot can read diffraction data from pdCIF files.


Spreadsheet text format (.csv)

This text spreadsheet format contains three columns of comma separated values, proceeded by a short file header. The first 2θ position (in degrees), second is intensity, and third is standard uncertainty for the intensity values (esd). This format may be conveniently opened in most spreadsheet or plotting programs.


Fullprof (.xy)

The Fullprof INSTRM=10 format containing three columns of data; position (in degrees), intensity, and sigma. The file begins with the keyword XYDATA, and the header also contains values for the INTER and TEMP keywords which enable use of sequential refinements with FullProf. Comment lines in the file header begin the "!" character.