Thank you very much.

There is no problem

Dear Tian,
If possible, please let me ask you a short question in SAPT-DFT:
To obtain DFT_Grac_Shift value for two interacting monomers, I am using PBE0/def2-TZVPPD level to optimize monomers geometry (and to obtain HOMO energy) and also to compute Vertical IP value. Then, DFT_Grac_Shift (in a.u.)= VIP(in a.u.)+E_HOMO(in a.u.).

Please let me know if you completely agree with the computational level I employed for mentioned purposes.

Sincerely,
Saeed