[Pw_forum] the problem of scf convergence

[hyello25 Qgrui]

hi,
  I performed other USPPs tests (blyp-van_ak, pw91-van_ak, pz-van_ak) and
found that all these calculations with USPPs were not convergence both in
press and Etot.For example, with blyp-van_ak( result is at the bottom of the
mail).All these USPPs are downloaded from the homepage of
PWSCF/pseudopotential.
  However, this unconvergence situation disappeared with NCPP (PBE-TM-GGA,
converted from fhi format PP using fhi2upf code). The result is at the
bottom as well.
  As Axel Kohlmeyer mentioned:
  "please try a different Li pseudopotential (i.e. a non-ak one).
the one you are using seems to have some not yet understood
problems for higher-order properties: lattice constant from
EOS fit, MD and geometry optimizations were fine, phonons
were bad."
  And can anyone tell me what does the 'ak'(in blyp-van_ak) mean? What kind
of systems are these 'ak' USPPs suitable for calculation?

WITH blyp-van_ak USPP:------------------------------------------------------
    ---!   convergence scf caculation for Li2O   !---
 ecutwfc = 100 Ry,  ecutrho = 320 Ry :
!    total energy              =   -61.82021122 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
19.03
 ecutwfc = 100 Ry,  ecutrho = 360 Ry :
!    total energy              =   -61.82317722 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -
6.75
 ecutwfc = 100 Ry,  ecutrho = 400 Ry :
!    total energy              =   -61.82694596 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
4.67
 ecutwfc = 100 Ry,  ecutrho = 600 Ry :
!    total energy              =   -61.82089409 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
4.29
 ecutwfc = 100 Ry,  ecutrho = 800 Ry :
!    total energy              =   -61.81983678 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
19.40
 ecutwfc = 100 Ry,  ecutrho = 1000 Ry :
!    total energy              =   -61.82031614 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
22.33
 ecutwfc = 200 Ry,  ecutrho = 800 Ry :
!    total energy              =   -61.82432402 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
9.13
 ecutwfc = 200 Ry,  ecutrho = 1000 Ry :
!    total energy              =   -61.82480674 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
12.09
 ecutwfc = 200 Ry,  ecutrho = 1600 Ry :
!    total energy              =   -61.82437317 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
6.83
 ecutwfc = 200 Ry,  ecutrho = 1800 Ry :
!    total energy              =   -61.82423710 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=
5.72
-------------------------------------------------------------------------------

WITH PBE-MT-GGA
NCPP:-----------------------------------------------------------
    ---!   convergence scf caculation for Li2O   !---
 ecutwfc = ecut = 50 Ry :
!    total energy              =   -33.53719310 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P= -
329.31
 ecutwfc = ecut = 80 Ry :
!    total energy              =   -33.60362083 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.81
 ecutwfc = ecut = 100 Ry :
!    total energy              =   -33.60420031 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
48.44
 ecutwfc = ecut = 140 Ry :
!    total energy              =   -33.60518304 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.36
 ecutwfc = ecut = 180 Ry :
!    total energy              =   -33.60525632 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
45.97
 ecutwfc = ecut = 200 Ry :
!    total energy              =   -33.60552604 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.30
 ecutwfc = ecut = 240 Ry :
!    total energy              =   -33.60553853 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.24
 ecutwfc = ecut = 280 Ry :
!    total energy              =   -33.60553917 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.23
 ecutwfc = ecut = 300 Ry :
!    total energy              =   -33.60553970 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.24
 ecutwfc = ecut = 340 Ry :
!    total energy              =   -33.60553987 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.23
 ecutwfc = ecut = 400 Ry :
!    total energy              =   -33.60554013 Ry
          total   stress  (Ry/bohr**3)                   (kbar)     P=  -
46.23
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