Hi,

The software VESTA is pretty good for this purpose (https://jp-minerals.org/vesta/en/). Here is a tutorial video.

https://www.youtube.com/watch?v=dBtq1GhOpd4&ab_channel=PhDzzz

After you created the supercell you can either export the data as a cif file and use the quantum espresso input file generator (https://qeinputgenerator.materialscloud.io/) or just export a 'P1' structure file that contains all atomic positions in cartesian coordinates and copy these in your quantum espresso input file.

HTH,

Johannes

As suggested by Johannes M. Meusburger, VESTA does an excellent job with crystal structure manipulation. However, if you want to expose a specific crystal plane, you must manually input the transformation matrix, which can be tricky at times ~depending on the complexity of the structure you're working with. So, keep an eye on BIOVIA Materials Studio for more automated and complex manipulations. I recently started using it and deeply regret not having access to it a long ago. MS really boosts productivity!

You can create super cell with the help of phonopy sofware using the command "phonopy --qe -d --dim="2 2 2" -c scf.in" . Important to note is that in scf.in, you have to set ibrav=0 (free lattice along with the lattice vector specifying your system's crystal symmetry). For more information please visit https://phonopy.github.io/phonopy/