Calculates extinction coefficients and writes a data file for
least squares
Description:
-
Reads one or more files containing reflection indices, structure factors
and their standard deviations. Each file may correspond to data measured
on a different scale or with a different wavelength. Using the given
wavelength, the program calculates the 4 coefficients involved in
the Becker Coppens extinction correction and writes a single file
containing the original hkl's stucture factors and esd'd followed by the 4
coefficients and finally a scaling zone number which is incremented by 1
for each input file given. In calculating CEXT(1) the program assumes
a constant path length of 2mm.
Input:
-
The crystal data file which must contain:
-
S cards
giving the symmetry
A
C card
with the cell dimensions
An
E card
indicating the type of extinction cerrection required
If the indices are non-integral
-
I cards
giving multipliers for the indices (MULx x=P,H,K or L),
- or a
Q PROP card
(as used in ARRNGE)
The data files containing lists of h, k, l, Fobs, esd(Fobs)
in format (3I5,2F10) or (3F8.3,2F10) for floating indices, these
are the formats written by ABSMSF.
Output:
-
The usual listing file reporting what was read from the CDF
An output file giving: h, k, l, Fobs, esd(Fobs), CEXT(i),i=1,4, iscale,
FORMAT (3I5,6F10.4,I5) or (3F8.3,6F10.4,I5) ie. suitable for input to
least squares programs in MODE 5 or 8.
Notes:
-
The scale factor allows data measured on very different scales to be
brought to approximately the same level. Useful if using unit weights in
least squares.
Note that this program does not deal with path dependent
extinction. AVEXAR should be used if the path dependence is thought
to be important.
Running the program:
-
On runung the program the user is asked for the name of the crystal data
file and then asked to choose a name for the output file. Following
that, for each input file, the user must give its name (default
extension .sf), the measurement wavelength and an optional scale
factor. Replying to this question with just "RETURN" terminates
the program.
Calls:
- ASK
EXTPAR
ICDFMT
INDFLO
INPUTI
LATABS
MESS
NOPFIL
PREFIN
RDREAL
RDWORD
RECIP
SYMOP
Common blocks used:
-
- /EXTN/ to use CEXT
- /IOUNIT/ to use LPT ITO
- /SCRACH/ to use all members
*** EXTCAL updated by PJB 18-Nov-1997 ***
Classification:
Specific Least Squares Refinement . . . . . . . Main Program
P. Jane Brown
e-mail: brown@ill.fr
Institut Laue Langevin,
Grenoble, FRANCE