I have been trying to simulate ZnSe zinc blende quantum dots using Quantum Espresso and its GUI BURAI. But being a beginner I am a little confused about a few things:

  1. How do I passivate the surface, am I supposed to make a new .cif file after deciding which substance I wanna use for passivation and what coordinates do I wanna place these atoms at.
  2. Do I even need passivation? I am trying to obtain optical band gaps for now.
  3. How do I apply vacuum to my quantum dot. This procedure is fairly simple for molecules but when I do the same for quantum dot(I have been trying to simulate one with 8 unit cells which make a bigger cube of sort, is this a correct way to make a quantum dot?) but when I do the same for a qd, the atoms which are there on the cubic lattice(Zn) also move with the surface hence destroying the bonds between them and ones on the inside(Se). How do I fix this??
    Thanks and I am a bachelors student who has not had any proper course(except for DFT one from coursera) in this and any other addvice would be greatly appreciated.