I calculated the optical properties for NiTiO3 using Quantum Espresso. Even though I did not use USPP, I still got the error: USPP are not implemented. How to fix? Thank. This is my nscf file.
Can you send me the scf input file and also the epsilon.x output file? It looks like the software is not recognizing the pseudopotentials you are using.
I recommend you perform the calculation again by employing PZ pseudopotentials instead of kjpaw. As you can see in the following, the PZ pseudopotentials are optimized to this end.
It is difficult to say something without seeing the outpu files of epsilon.x and nscf calculation. In you nscf calculation input file, everything is OK. I think you need to attach also output files to this discussion.