ATAT installation

ATAT and Atomsk should be downloaded from their respective websites given in the Dislcaimer section.
Other interesting repositories can be found on my personal website: sufyanshk.github.io

I suggest to install ATAT in the /bin/ directory so that all the users can use it. If you don't edit the makefile of ATAT then only the user who installed it, can use it.
Execute these commands sequentially (so that all the users will be able to use ATAT):

bash
cd atat  
sed -i '' '1s/\$(HOME)//' makefile #if OSX  
sed -i '1s/\$(HOME)//' makefile #if linux  
make  
make install  

Generate POSCAR file using Atomsk

#will create bcc W unit cell and will orient it along xyz, abc, pqr directions
atomsk --create bcc 4 W orient [x y z] [a b c] [p q r] pos

#will duplicate the unit cell along its axes
atomsk POSCAR -duplicate 2 2 2 # repeat the unit cell twice in x, y and z directions

rndstr.in from POSCAR generated by Atomsk

For generating supercell of specific dimensions, mcsqs requires rndstr.in file of the required supercell. The file make_rndstr.in edits the POSCAR file generated from atomsk code and creates the rndstr.in file.
Check the rndstr.in file before starting the calculations because sometimes the code can delete some of the lattice parameter values present in the first 3 lines of the generated rndstr.in file.
This rndstr.in can then be given as input to mcsqs to generate the SQS of required dimensions.
(Note: All the atomic sites in rndstr.in file should be given the relative concentration of the chemical species, according to the alloy chemistry. This should be done manually using sed or awk to avoid any mistakes.)

MCSQS from ATAT

I have added a file named check_sqs.sh which checks whether the Perfect_match for the correlation is found or not. If the Perfect_match is found in the bestcorr.out file, then the code creates a file named stopsqs. If the mcsqs code is running and when it sees the file stopsqs, then it cleanly stops its run. Included also is the sqscell.out file, which ensures that only one supercell is created according the rndstr.in file.

mcsqs -2=... -3=... #depending upon your requirements it can be pairs, triplets, etc.
mcsqs -rc

In the check_sqs.sh file you can define for how many seconds the mcsqs code should keep finding out the sqs'es. (I have put the default as 172800 seconds which is equal to 2 days)

Disclaimer

The ATAT code can be downloaded from ATAT's official website.
The Atomsk code can be downloaded from Atomsk's official website.
ATAT and Atomsk are the property of their respective creators.
No copyright infringement intended.