I am trying to perform DFT calculations on lead halide perovskite system using Quantum Espresso However, I am confused in choosing the pseudopotentials. The hybrid pseudopotentials are recommended to use but I am unable to find the hybrid pseudopotentials. Is there any library for hybrid pseudopotentials?
It is suggested to use other pseudopotentials (such as PBE) and put input_dft variable in &SYSTEM card. What will change in the calculations by putting this variable?
TLDR: enforce the hybrid functional using input_dft keyword. Check the exchange-correlation (XC) functional of your hybrid functional and use any pseudopotentials that has the same XC functional.
From Quantum ESPRESSO's FAQ:
2.7 WHERE CAN I FIND PSEUDOPOTENTIAIS FOR HYBRID/NONLOCAL FUNCTIONALS? Short answer: nowhere, for the time being. Use pseudopotentials for the non-hybrid functional that is closer to the hybrid you like: PBE for PBE0 and HSE, BLYP for B3LYP. Same for nonlocal (e.g. vdw-DF) functionals: use pseudopotentials generated for the closest GGA functional.
This means there is no special pseudopotentials for hybrid calculation. You need to use the keyword input_dft in the &SYSTEM namelist to specify the type of hybrid functional you are using. Every hybrid functional has two parts: one coming from the exact exchange and the other coming from some other sources. The pseudopotentials should be chosen from the set of regular pseudopotentials that has the same other XC functional. For example, HSE06 or PBE0 or gauPBE functionals are formed from a combination of PBE functional and exact exchange. So, you should set input_dft='hse' or input_dft='pbe0' or input_dft='gaup', respectively and use any pseudopotentials with PBE XC functional. See this for a list of all allowed values for input_dft keyword.
If you do not put your preferred hybrid functional in the input_dft variable, then QE will assume that the calculation is not done with hybrid functional and it will read the functional from the pseudopotential file. So, if you use a pseudopotential with PBE functional and leave the input_dft unspecified, then it will give you a regular PBE level result. You use the input_dft keyword to specify that you are using a hybrid functional.
