The purpose of a Instrument parameter file is to set default values
for that instrument. These files are described in the GSAS manual
(p158 in the 1990 version, p176 in the 1994 version).
Below are two files, one for a CW neutron instrument and one for a
synchrotron instrument. I will try to explain what I know.
BANK It is possible to describe several different instrument
configurations in a single file and then select the appropriate
bank number. In most CW cases this is not needed.
Data for bank 1 is prefixed by "INS 1..." Data for bank 2
would be "INS 2..."
The HTYPE statement describes the type of data.
The first letter is P for powder S for single xtal
The second letter is N or X for neutron or X-ray
The third letter is T for TOF or C for CW
I forget what the 4th letter is for, I think it means ready for use.
The ICONS entry (for CW) describes wavelength1, wavelength2, zero and POLA
(change these values in the overall parameters-instrument
constants menu)
The "I HEAD" entry can have any text
The "I ITYP" entry describes an incident spectrum correction needed
for energy dispersive but not CW instruments.
Put 0 as the 1st number and
your maximum 2theta range for the second two numbers
the 4th does not matter.
"INS 1 IRAD" specifies a x-ray radiation type. Use 3 for CuKa radiation.
The "INS 1PRCFnn" defines the default profile parameters where the
first set specified is the default.
on the first card ("INS 1PRCF1" or "INS 1PRCF2") the entries are
profile#, # of parameters, cut-off
the remaining cards are the profile parameters for that profile function
(U, V, W,...)
The best way to set these is to complete a refinement on a standard with
pretty sharp peaks and then copy the values from the .EXP file (see below).
Change the prefix "HAPn" to "INS ". With good data and a reasonable structure,
you can start a refinement with pretty rotten starting values and then fit
them. Start by fitting W only... You probably won't be able to refine V with a
conventional instrument.
in .EXP file:
HAP1 1PRCF 2 12 0.00500 0YYYNYNNNNNNNNNNNNNNN
HAP1 1PRCF 1 0.205738E+03 -0.160655E+03 0.117736E+03 0.000000E+00
HAP1 1PRCF 2 0.103780E+02 0.000000E+00 0.500000E+01 0.000000E+00
HAP1 1PRCF 3 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00
CW Neutron instrument parameter file:
-------------------------------------
INS BANK 1
INS HTYPE PNCR
INS 1 ICONS 1.54020 0.00000 0.04000 0
INS 1I HEAD NIST BT-1 instrument
INS 1I ITYP 0 5.0000 168.0000 1
INS 1PRCF1 1 6 0.00500
INS 1PRCF11 0.179000E+03 -0.301000E+03 0.181000E+03 0.500000E+01
INS 1PRCF12 0.000000E+00 0.000000E+00
INS 1PRCF2 2 12 0.00500
INS 1PRCF21 0.179000E+03 -0.301000E+03 0.181000E+03 0.000000E+01
INS 1PRCF22 0.000000E+00 0.000000E+00 5.000000E+00 0.000000E+00
INS 1PRCF23 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00
Synchrotron Neutron instrument parameter file:
----------------------------------------------
INS BANK 1
INS DTYPE STND
INS HTYPE PXCR
INS 1 ICONS 1.540510 0.000000 0.0 0
INS 1 IRAD 0
INS 1I HEAD DUMMY INCIDENT SPECTRUM for x7a
INS 1I ITYP 0 0.0000 150.0000
INS 1PRCF1 2 12 0.01
INS 1PRCF11 0.000000E+00 0.000000E+00 0.800000E+02 0.000000E+00
INS 1PRCF12 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00
INS 1PRCF13 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00
Hope this helps,
Brian
-- ***************************************************************************Brian H. Toby Reactor Radiation Division E151/235Brian.Toby@NIST.gov National Institute of Standards & Technologyvoice: 301-975-4297 FAX: 301-921-9847 Gaithersburg, MD 20899***************************************************************************