[Pw_forum] question about vacuum distance

[xywu]

  Dear all,

   I've a question about the pwscf.
   In calculation of surface, the slab model is used.  After pp.x and
chdens.x, the charge density and DOS at fermi surface can be  visualized  by
Xcrysden.
  My queation is about the distance between slabs and whether the charge
density of two slabs is overlapped.  Is the charge density in vacuum  region
is less than 1E-8  or equal to zero? When an external electric field is
added, how to check the distance between slabs is enough.



 Thank you in advance!

xywu
e-mail: xywu at imr.ac.cn