cif2cell (GitHub) is a tool to generate the geometrical setup for various electronic structure codes from a CIF (Crystallographic Information Framework) file. The code will generate the crystal structure for the primitive cell or the conventional cell. It can generate CASTEP CELL input files from CIF files. It is included in the CASTEP academic source bundle. Since CASTEP is proprietary code, the input files sometimes cause problems when using ASE or VESTA. Also, cif2cell works better for creating CELL supercells.
It seems to cause problems in Windows, so you may want to use Windows Subsystem for Linux (WSL) to run it on that platform. You can download Linux distros such as Ubuntu for WSL from the Microsoft Store.
On Linux, install with:
pip install cif2cell -U
You can use cif2cell to create a CELL file from a CIF file.
You can create a supercell in the process with an extra argument, replacing k,l,m with the size of the supercell.
Additionally, you can specify the output name with the -o tag.
cif2cell TEST.cif -p castep --supercell=[k,l,m] -o TEST.cell
To translate the cell,
cif2cell TEST.cif -p quantum-espresso --supercell-translation-vector=[k,l,m]