I am attempting to determine the phonon density of states (via DFPT method) of a relatively large unit cell (52 atoms) using Phono3py from my VASP outputs. However, attempts to produce even a simple supercell (2 1 1) from the POSCAR using a recommended method, with command:

phono3py -d --dim="2 1 1"

This results in 27754! POSCAR files and the SPOSCAR before the memory runs out and no more can be printed (so, no phonopy_disp.yaml). What am I doing wrong? I do not think I can make the unit cell smaller for this structure.