The easiest way to write down a suitable info.inp file for the analysis is by using the smart program (command s at the prompt in the interactive mode). Note that smart reads the DATA.INP file (so, any hkl file must be copied to it with the c command, at the equiv prompt) which should be in free format to avoid problems (you can transform it by means of the tras program).
In the Interactive and Batch modes (Linux/Unix version) the smart program is interactive, whereas in the graphical mode a form is displayed, to be filled with the relevant parameters.
Smart will ask for the cell parameters, the wavelength, the cut-off for the intensity distribution, which will be used to supply good values to the INTS card so that, on average, the intensity intervals over which the reflections will be divided (see the INTS card in the Keywords section) are set up in such a way that an equal number of reflections will fall in each interval. If the data file contains a lot of very weak reflections, in order to have a good distribution it is better to exclude them from this initial stage, by providing a suitable cut-off (which has to be found by trial; a value of 30. or 40. is generally good).
Then the title (for an initial TITL card), the point group (the symbol according to the TABLE), the percentage difference (perc parameter of the STAT card), the cut-off (ctf parameter of the STAT card) and the printing cut-off (lim parameter of the SHOR card) are required.
At this point, the file info.inp is generated (and can be modified by editing it).
The file equiv.prp, recording some key information of this preliminary stage, is also generated and is visible with the command e (in the graphical mode, equiv.prp is displayed in the console window of the Interface). Here is an example of equiv.prp obtained for a 4/m sample system:
Smart program - Unix version - Rel. 1.0 1/1/97
By M. Prencipe
Enter cell (a b c alpha beta gamma)
15.5320 15.5320 11.8210 90.0000 90.0000 90.0000
Enter wavelength
0.71069
Enter cutoff for intensity distribution
30.00
12313 reflections read. Theta min.: 2.2 Theta max.: 30.1
9210 reflections with int. higher than 30.0
0
reflections with int. less than 0.
Max. intensity: 20007.0 Min. int.: 30.0
Number of vectors per group: 2462
1) theta min.= 2.165 theta max.= 11.306 vect. 2464
2) theta min.= 11.307 theta max.= 17.128 vect. 2459
3) theta min.= 17.129 theta max.= 20.956 vect. 2459
4) theta min.= 20.957 theta max.= 25.865 vect. 2462
5) theta min.= 25.866 theta max.= 30.076 vect. 2469
Distribution of intensities on 10 intervals:
Mean num. of refl. for group: 921
N: 1252 1140 924 969 925
961 955 923 922 240
I: 43. 89. 129. 190. 290. 490. 889. 2346. 14108. 20007.
Smart ended, file info.inp generated.
The distribution of intensities is the point to be noted: the cut-off was chosen to be 30. so that the analysis was performed on 9210 reflections, with intensity higher than 30., out of 12313 total reflections; 10 intervals were defined with an average number of reflections of 921 for each one; only the first 2 intervals and the last one contain a number of reflections somewhat different from 921, but these differences are not so dramatic. If a value of 0 had been chosen for the cut-off, the results would be even worse:
Distribution of intensities on 8 intervals:
Mean num. of refl. for group: 1231
N: 3148 1568 1528 1281 1305 1258 1232
994
I: 9. 60. 121. 200. 381. 823. 3529. 20007.
that is: only 8 intervals and an even more uneven distribution. The right value for the cut-off should be chosen by trial, in such a way that a distribution comparable to the sample one is obtained.
The info.inp file obtained from this sample is shown below:
TITL
Sample system
CELL
15.532 15.532 11.821 90.000 90.000 90.000 0.710690
SYMM
14
EVAL
8 0
THET
1.66494 11.30607 1
THET
11.30707 17.12847 2
THET
17.12947 20.95555 3
THET
20.95655 25.86537 4
THET
25.86637 30.57637 5
SHOR
50
ORDT
COPY
0 1 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 2 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 3 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 4 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 5 0
STAT
1 1 1 0
2 10.0 0.0
INFO
SETZ
WEAK
8
SHOR
0
COPY
6 0 0
INTS
10 43. 89. 129. 190. 290. 490. 889. 2346. 14108. 20007.
SIGM
1 3 2
COPY
0 1 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 2 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 3 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 4 0
STAT
1 1 1 0
2 10.0 0.0
COPY
0 5 0
STAT
1 1 1 0
2 10.0 0.0
Look at the keywords section for a detailed explanation about each card in info.inp. The main points are:
- the symmetry selected is 14 (4/m, see the TABLE).
- The initial data file DATA.INP is splitted in 5 file DAT0i.OUT by the THET cards: the itr values (see THET card in the Keywords section) are evaluated by smart. Instead of the five THET card, a single SMRT card could be used, without any input parameter: this avoids the use of the smart program to find best theta values for the repartition.
- The file DAT01.OUT is copied in DUMMY.INP and an analysis of the reflections contained in it is performed (STAT card) marking all the reflections having intensities which differ from the average by more than 10%; such reflections are written in DATA.DBL if the ratio normal/anomal is greater or equal to 2.
- Then the second file DAT02.OUT is copied in DUMMY.INP, etc....
- As the last file has been analysed, a summary statistic is shown (INFO card) and the statistical variables are set to 0 (SETZ).
- The reflections contained in DATA.DBL are eliminated from DAT0i.OUT (WEAK) so that clean DAT0i.END files are generated; these files are copied back to DAT0i.OUT.
- The evaluation of the standard deviation from the equivalents is then prepared by means of the INTS and SIGM cards.
- The analysis restarts showing only summary statistic (SHOW 0), without writing any reflections in DATA.DBL and evaluating the new standard deviations according to the scheme specified by SIGM.