chi90s

chi90s is a program which searches through a CAD4 data file trying to find reflections which are suitable to use as psi scan reflections. The new twist on this is that if a reflection meets certain preliminary criteria, but does not have a suitable chi value, the program then calculates the chi values for the non-Friedel symmetry equivalents. If one of these symmetry equivalents are suitable, then that reflection is output.

The preliminary criteria are a minimum net intensity and a maximum theta value. Sensible defaults are set by the program (see chi90s.h file), and can be changed with command line options. Here is a list of options: 

-c   -- specify minimum chi value.
-h            -- gets  a help screen.
-i  -- specify minimum net intensity.
-t -- specify maximum theta value.
-s            -- include symmetry equivalent reflections.
-u            -- unique data (use only data in cad4 data file).
-f  -- use filename as output file.
Options -c, -i, -t take mandatory numerical arguments. Option -f takes mandatory argument.

An example of use is shown below:

chi90s -t15 -i900 -s x96017.dat
In this case the -t15 option tells to program to disregard all reflections which have theta greater than 15 degrees, and the -i900 option tells the program to use reflections which have a net intensity above 900. The -s option tells to generate symmetry equivalents. The -s option invokes an input dialog to specify the Laue group. Output from that command is written to a file and looks like this:

Minimum Chi             =   80.00
Minimum Intensity       =  900.00
Maximum Theta           =   15.00
CAD4 Data File          = x96017.dat

 Nrefl   h   k   l      Theta     Chi      Int          sigI    SymmEqv (*)
    50   0   1   1       2.56   -86.83    4663.3        41.23
    93   0   3   3       7.69   -86.83    7612.7        51.75
   101   0   4   4      10.28   -86.83    1068.0        20.31
   102   0   4   5      10.98   -81.12    2655.0        30.97
   135   0   5   4      12.30   -87.69    1506.3        24.04
   136   0   5   3      11.82   -82.18    1713.0        25.37
   147   0   6   4      14.40   -84.09    1286.3        22.26
   461  -1   6   5      14.92   -84.44    2884.7        32.63      *
   543  -1   4   4      10.31   -81.83    2309.7        29.02      *

Wavelength:      0.710730 angstroms
Filter Factor:  19.090
Orientation Matrix:
                 0.065709 -0.029181  0.034949
                -0.040978 -0.039247  0.043276
                -0.003178 -0.097293 -0.027914
The asterisks (*) for the last 2 reflections, indicates these are symmetry equivalents generated by the program.

The program is written in ANSI C and uses the getopt(3) library function available on most Unix systems to parse the command line. If you are compiling for a system which does not have getopt(3), then edit the Makefile to include -DNO_GETOPT in the CFLAGS variable definition. This option then causes the program to use an input dialog to get information from the user.

The program assumes that normal crystallographic conventions are being adhered to, i.e. b axis is unique in monoclinic, and c axis is unique in symmetries higher than orthorhombic.

Requirements for use:

The program is free of charge, however donations are always welcome. In addition, the following stipulations apply:

Paul D. Boyle
boyle@laue.chem.ncsu.edu
27 August 1997