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Methods, Problems and Solutions

GSAS (General Structure Analysis System) Rietveld powder diffraction and Single Crystal software

GSAS - using Energy Dispersive Diffraction Data with GSAS

The CCP14 Homepage is at http://www.ccp14.ac.uk

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[The reference to use for GSAS in any resulting publications is: A.C. Larson and R.B. Von Dreele, "General Structure Analysis System (GSAS)", Los Alamos National Laboratory Report LAUR 86-748 (1994).]

Example GSAS Energy Dispersive X-ray Diffraction files


Hints and advice on using Energy Dispersive Diffraction Data with GSAS by Yusheng Zhao

Date: Mon, 30 Apr 2001 14:40:32 -0600
To: Lachlan Cranswick [lachlan@ldeo.columbia.edu]
From: yzhao@lanl.gov (Yusheng Zhao)
Subject: Le Bail refinement for EDX 


Dear Lachlan,

The following are something I prepared for GSAS users who want to analyze 
their energy dispersive data.  Hope it can help.

*****************************************************

The general approach to refine energy dispersive x-ray diffraction data

The GSAS package has a program called "x17bcnv.exe" which is used for 
converting the energy dispersive data "***.mca" collected at X17b, NSLS, to 
the GSAS format "***.dat". The GSAS formated data file will be recognized 
by current GSAS program.

Presently, we use LeBail (not Rietveld) technique to refine the energy 
dispersive x-ray diffraction data, which ignores intesity information. 
Therefore, the GSAS can only refine peak positions and lattice constants, 
and no refinement on atomic positions. Multiple phase mixture can also be 
refined. We are working on the technique to refine structure using energy 
dispersive data. It is not ready yet.

Attached are an original X17b data "jddi1004.mca" and the converted GSAS 
data "jddi1004.dat". Also attached is a instrument file for the energy 
dispersive data "inst_x17.prm". You should be able to figure out how to 
convert your data from there.

The energy dispersive data of NSLS X17B (Stony Brook) format (jddi1004.mca) 
can be converted to GSAS format (jddi1004.dat) using the X17BCNV.EXE in 
GSAS/exe package. One may try to convert his/her file to NSLS X17B format 
first and then run X17BCNV.exe to make GSAS format. After the convertion, 
he/she needs to use "inst_x17.prm" as the parameter file for the input.

**************************************

The header of "jddi1004.dat".

jadeite ambient 1995: 2: 9: 7:46:58 5.85335
BANK 1 2047 205 EDS 1.44982E-01 6.16793E-02 -2.91062E-07 1.23442E-10 STD

The 5.85335 is 2-theta for EDS data, only spaces after it in the first line.

Second line has polunomial fit of channel(start from ch.0 up to ch.2047) to 
energy(KeV).

Energy cal. parameter 1 0.14498218156313670E+00
Energy cal. parameter 2 0.61679316154140906E-01
Energy cal. parameter 3 -0.29106203137951869E-06
Energy cal. parameter 4 0.12344200227292932E-09

They are truncated to 5 digits after the decimal point in ".dat"

**************************************

The instrument parameter file: "inst_x17.prm"

123456789012345678901234567890123456789012345678901234567890
INS BANK 1
INS 1 IRAD 0
INS HTYPE PXER (indicate Powder X-ray Energy Dispersive)
INS 1 ICONS 5.8472 (indicate Two-Theta angle)
INS 1I HEAD DUMMY INCIDENT SPECTRUM FOR EDS DIFFRACTOMETER
INS 1I ITYP 0 0.0000 150.0000 1
INS 1PRCF1 1 4 0.01
INS 1PRCF11 0.173000E-03 -0.161000E-01 0.401000E+00 0.000000E+00
(indicate initial profile function)

Inside GSAS, you need to turn on the LeBail switch following the steps:

L - Least square refinement set up
L - Edit least square controls
E - Change poweder data Fobs extraxtion flags
C - Change Fo extraction method flages
& entering 1 for LeBail method.

Best Regards.

Yusheng Zhao.


Using Energy Dispersive Diffraction Data with GSAS

Via Rietveld Mailing List

Date: Tue, 20 Jun 2000 16:38:37 -0400
To: [rietveld_l@ill.fr]
Subject: Conversion from Synchrotron to GSAS
Content-Disposition: inline

Hi everybody,

I have question regarding the synchrotron data.  I'd like to convert the Energy
Dispersive Data from Synchrotron to GSAS file.  It composes of energy (keV) and
intensity count.  What program should I use? Can anybody help me?

Regards,
Walairat


Subject: Re: Conversion from Synchrotron to GSAS
To: rietveld_l@ill.fr
Date: Wed, 21 Jun 2000 11:01:12 +0100 (BST)
Precedence: list
Reply-To: RIETVELD_L Distribution List [rietveld_l@ill.fr]


> I have question regarding the synchrotron data.  I'd like to
>convert the Energy Dispersive Data from Synchrotron to GSAS
>file.  It composes of energy (keV) and intensity count.
>What program should I use? Can anybody help me?
>
> Regards,
> Walairat

I would be interested in the procedure for GSAS to handle
Energy Dispersive data in a native fashion.

PowderX by Cheng Dong  and Powder v 2.00 by Nita Dragoe
can view, analyse and manipulate Energy Dispersive data
in a native fashion.

PowderX:
  http://www.ccp14.ac.uk/tutorial/powderx/

Powder v 2.00
 Tutorial:
   http://www.ccp14.ac.uk/tutorial/powder/index.html
Download:
   http://www.ccp14.ac.uk/ccp/web-mirrors/ndragoe/html/software.html

=====

To trick other software into being able to use energy
dispersive data - you could convert it into an angular

dispersive equivalent - which in theory any common diffraction
software could then use to a limited extent.

DLConvert for Windows can do this on Daresbury SRS and Argonne
format Energy Dispersive data.
  http://www.ccp14.ac.uk/projects/dl-conv/
The latest version has some minor bugs that a new
student programmer will be fixing next month and the
best version to get for the moment is 1.26:
  http://www.ccp14.ac.uk/projects/dl-conv/Dlconv1-26.exe

It will also do interpolation of the data into
constant steps when going from Channels/KeV to
2-theta format.

Lachlan.

--
Lachlan M. D. Cranswick

Collaborative Computational Project No 14 (CCP14)
    for Single Crystal and Powder Diffraction
Daresbury Laboratory, Warrington, WA4 4AD U.K
Tel: +44-1925-603703  Fax: +44-1925-603124
E-mail: l.cranswick@dl.ac.uk  Ext: 3703  Room C14
                           http://www.ccp14.ac.uk


Date: Wed, 21 Jun 2000 09:11:01 -0600
To: RIETVELD_L Distribution List [rietveld_l@ill.fr]
Subject: Re: Conversion from Synchrotron to GSAS
Precedence: list

Lachlan (and others),
GSAS will handle "native" energy dispersive data just fine. The raw data is
in the "standard" GSAS format (10 fields of 8 characters) with intensities
measured in constant energy steps. The "BANK" record looks like the following:

BANK 1 2047  205 EDS  1.67141E-01  6.13157E-02  4.89310E-08 -3.53527E-12
STD

The four values after "EDS" are the coefficients for the equation

E = c(1)+c(2)*s+c(3)*s^2+c(4)*s^3

that converts step number (s) to energy in keV. These coefficients must be
determined for each instrument setup by calibration with a standard
material. Changing 2theta for the detector will change these values. If the
measured intensities are "precorrected" then the alternative "ESD" data
format can be used instead.
The instrument parameter file for EDS data looks like:

             123456789012345678901234567890123456789012345678901234567890

NS   BANK      1
INS  1
IRAD     0
INS   HTYPE   PXER

NS  1 ICONS   7.81476
INS  1I HEAD  DUMMY INCIDENT SPECTRUM FOR EDS
DIFFRACTOMETER
INS  1I
ITYP    0    0.0000  150.0000         1
INS  1PRCF1     1    4      0.01

NS  1PRCF11   0.173000E-03  -0.161000E-01   0.401000E+00   0.000000E+00

A copy of this file is in the gsas distribution material as
\gsas\example\inst_x17.prm.
One should change the value on the "ICONS" record to what ever 2theta value
the detector was positioned at for your experiment.
Bob Von Dreele


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