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PROGRAM AVEXAR

To read ARRNGE files and prepare for LSQ with extinction

Description:

The program will read one or more of the files written by ARRNGE or ARRINC and prepare a file for LSQ in which equivalent reflections are treated independently so that a path-length dependent extinction correction can be refined. It will average reflections which have been measured more than once. If the data are intensity measurements, and "G" cards are present on the crystal data file, absorption factors will be calculated and applied. In all cases the 4 constants needed for Becker Coppens extinction corrections will be calculated. If no "G" cards are present a standard path length of 2mm is used. The data are written in a form suitable for input to the CCSL least squares programs (SFLSQ, MAGLSQ etc.).

Input:

The crystal data file must contain:
S cards giving the symmetry
A C card with the cell dimensions
An I DTYP card describing the type of data (the same as used for
ARRNGE) it is only used to determine whether the data are flipping ratios or intensities and how many additional parameters such as angles were stored by ARRNGE

An E card indicating which type of extinction is to be used (Gausssian,
Lorentzian etc.)

D cards describing the diffraction geometry
G cards describing the crystal shape. These are optional and if absent no
absorption corrections will be made and a constant path length of 2mm will be assumed.

If the data are for a magnetic structure with non-integer indices a Q PROP card giving the propagation vector is required.

Basically the same crystal data as that used with ARRNGE to produce the input file should be used but with the addition of E, D and G cards . The data input is one or more files written by one of the ARRNGE type programs. Different files may correspond to different measurement wavelengths, but they should all have the same crystal orientation and measurement geometry.

Output:

The usual listing file reporting data read from the CDF. A file of averaged and (possibly absorption corrected) data suitable for input to one of the least squares programs L MODE 5 for integer indices and L MODE 8 for floating indices. This file has default extension .sf for structure factors and .fr for flipping ratios.

Notes:

This program replaces the three similar programs ABSEXF, ARREXF and AVEXTR

Running the program:

On running the program the user is asked for the name of the crystal data file and then for each data file: its name, the measurement wavelength and a possible scale factor. This latter is to allow data on very different scales to be scaled to approximately the same level, a scale of unity is usually OK. Each data set will be given a different scaling code so there should be one entry on the L SCAL card for each set.

Calls:

ASK DUMMY ERRMES ICDFMT INPUAR INPUTI LENGT NOPFIL ONCARD PATHS PREFIN RDREAL RDWORD RECIP SETABS SYMOP

Common blocks used:

/ABSDAT/ to use MODEA
/IOUNIT/ to use LPT ITO LUNI
/REFS/ to use SCALE INC ITEMS
/SCRACH/ to use all members

*** AVEXAR by PJB 14-Nov-1997 ***

Classification:

Data Collection and Reduction . . . . . . . Main Program

SUBROUTINE PATHS(IG,DOABS,ISFLIP)

Calls:

ABMULT EXTPAR GMEQ INDFIX WTMEAN

Called by:

AVEXAR

Common blocks used:

/DIRCOS/ to use all members
/EXTN/ to use CEXT
/IOUNIT/ to use LPT LUNI
/REFS/ to use LL SCALE INC II
/STATS/ to use WRK2

*** PATHS by PJB 10 Apr 87 ***




Contents Manual

P. Jane Brown e-mail: brown@ill.fr
Institut Laue Langevin,
Grenoble, FRANCE