Dear Mingchao Wang, as far as i know, the best case is to use Pseudopotentials of the same kind for all atoms, and preferably full-relativistic, so the spin-orbit coupling can be accurately taken into account, since it its known that Eg calculated without relativistic spin-orbit coupling is , although not very different that the no-relativistic calculated one due to cancelling over- and under- estimation issues in non-relativistic pseudopotentials, not a good obtained one. Long words short: you're getting a Eg value from a not so much physically accurate calculation framework.
On the other hand, you not need to use H atoms to calculate Band Structure, since their contribution is only in the deep levels of valence and conduction bands (not near the band gap), unless you are into studying deep band structure actually. Finalliy, I think that noncolin=true is a must for spin-orbit calculations in pw.x , but i'm not 100% sure if that's true for an hybrid inorganic-organic system such as a CH3NH3PbI3 unit cell crystal at any temperature and crystal system of those this material can form. Anyway, Would you mind to put your pw input file, so i can compare my calculations with yours, since i'm currently working on the same system? that would be very very helpful to me and for others fellows in the forum and all would help you more and better, also. Best regards, Josué Clavijo, PhD. Assistant Professor Universidad Nacional de Colombia _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
