McMaille is a program for indexing powder patterns by Monte Carlo and grid search (maille in french = cell in english). The necessary data file is quite simple in automated black box mode :

Running McMaille (by either clicking on McMaille.exe and giving the entry file name - no extension - or in a DOS box by typing "McMaille name" ) requires a parameters data file. A typical data file (should be named name.dat, name being your choice) follows :

Typical name.dat input file :

SR2CR2O7                       Title
1.54056 0.0 3                  Wavelength, Zeropoint, Ngrid
!!!                        A line starting by ! is ignored
11.180   345.                  2-theta, Intensity
12.217  1120.                  Etc
15.835   124.                  20 couples of positions and
18.709   455.                     intensities. You may put more
Etc                               but only 20 will be used.          

Line 2 :
Wavelength : your experiment wavelength. If you used CuKalpha, you should have stripped alpha2 before peak positions hunting.

Zeropoint : your powder pattern zeropoint (global value including the zero due to the diffractometer and the zero due to sample misplacement - will be added to the data). It is recommended to have a standard compound mixed with your sample or to apply the harmonics method for zeropoint estimation.

Ngrid : code for the process to be applied
             Ngrid = 3 : black box mode - Monte Carlo on all symmetries (recommended)
             Ngrid = 4 : black box mode - Monte Carlo on all symmetries + grid search

Next lines :
2-theta and intensities couples of values.

McMaille produces 4 or 5 types of output files :

name.imp   containing the details of the calculations and a final sorted summary. 
                   There are 2 verbosity levels, low and large. The large verbosity is
                    obtained by entering a negative wavelength (of which of course the
                    sign is then immediately changed).
name.ckm  containing an ordered total list of the "best cells" for the CHEKCELL 
                   program. Note that the FoMs are not real FoMs, but are calculated
                   as the inverse of Rp multiplied by 5... A pseudo-FoM larger than 20
                   is a priori interesting, corresponding to Rp < 25%. A pseudo-FoM
                   close to 50 or larger may indicate the correct cell (Rp < 10%).
                   Depending on the cell proposals, partial lists are also built ;
                      name_cub.ckm  :  cubic
                      name_rho.ckm  :  rhombohedral
                      name_hex.ckm  :  hexagonal/trigonal
                      name_tet.ckm    : tetragonal
                      name_ort.ckm    : orthorhombic
                      name_mon.ckm  : monoclinic
                      name_tri.ckm      : triclinic
                      name_two.ckm   : two phases mode output (manual mode)
name.mcm containing an ordered list of the "best cells" for CRYSFIRE.
name.prf    containing the "best profile" result (with lowest Rp), to be seen by the 
                   WINPLOTR program. For this calculation, Gaussian peak shape is 
                   used, having FWHM = W / 2, where W is the mean columnar width 
                   above (given that it is recommended to use W = 2 * FWHM as a 
                   minimum). The calculated pattern is obtained after 4 Le Bail fit 
                   iterations.
name-new.dat produced only for NGRID=3 or 4 (black box mode), containing 
                  control parameters for new searches with NGRID = 2 in cubic 
                   symmetry.

The screen output delivers for each symmetry examined the first cell proposal,
and then all the proposals which will correspond to a Rp decrease. This means
that the true cell may not appear here if a false one having a smaller Rp value
is encountered before it. Anyway, the screen output will give you an idea of the
smaller Rp attainable. Then look at the name.imp file and to its sorted summaries.

This black box mode should solve simple cases. If not, use the manual modes (NGRID = 0, 1 or 2).

For recognizing the very best solution in a black box mode output, you have to find, in principle, the cell proposal corresponding to the smallest Rp with highest symmetry and smallest volume, indexing the largest number of peaks. Not always an easy task... so, open your eyes ! Then check your choice(s) by the Chekcell program and by whole pattern fitting by the Pawley or Le Bail methods (Fullprof, Gsas, Rietica, Maud, etc, etc).

NOTE : pressing the K keystroke (capital letter - for Kill) will stop the program a few seconds later, saving the current results.