[Pw_forum] the problem of scf convergence

[hyello25 Qgrui]

hello, everyone.
  These days, I performed the convergence of scf calculation with some USPP,
but never see a good ecut convergence. The system only contains 3 atoms,
with 12x12x12 kpoints automatic generated in MP grids.
  Why does the press differ each so mush? Is 200ev Ry too high for USPP? And
which press is more convictional?
  Can anyone give me some suggestion? Thanks in advance.
 ecut=80 :
!    total energy              =   -61.89999202 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
0.59
 ecut=100 :
!    total energy              =   -61.90651146 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -
5.39
 ecut=140 :
!    total energy              =   -61.90331161 Ry
          total   stress  (Ry/bo hr**3)                   (kbar)     P=
0.97
 ecut=180 :
!    total energy              =   -61.90482904 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
10.64
 ecut=200 :
!    total energy              =   -61.90542701 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -
4.55
 ecut=240 :
!    total energy              =   -61.90875043 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
5.92
 ecut=280 :
!    total energy              =   -61.90854533 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
1.68
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20070913/7ecef9a0/attachment.html>