[Pw_forum] conversence problem in vc-relax (Atom Mass in relaxation)

Yukihiro Okuno okunoyukihiro2000 at yahoo.co.jp
Sat Sep 8 18:02:49 CEST 2007


Dear PWScf Users.

I'm Yukihiro Okuno.

I had posted about the Atom Mass in vc-relax, and thank you for the responces.
We set same atom mass 20.0 ( average of atom mass), and do vc-relax calculation as
the following input file,


&control
    calculation  = 'vc-relax',
    restart_mode = 'from_scratch',
    pseudo_dir   = '/pseudo/',
    outdir       = './', 
    prefix='vc-test'
    nstep = 100
    etot_conv_thr = 1.0D-5
    forc_conv_thr = 1.0D-4
    dt = 80.0
    tstress = .true.
    tprnfor = .true.
  /
 &system
    ibrav=6
    celldm(1)=6.83994507291
    celldm(3)=1.09801321247
    nat=5
    ntyp=3
    nbnd=26
    ecutwfc=60.0
    ecutrho = 600.0
    occupations = 'fixed'
    degauss=0.00
 /
 &electrons
    conv_thr = 1e-10,
    mixing_beta=0.3,
 /
&IONS
 ion_dynamics='damp' 
 bfgs_ndim=3
 pot_extrapolation = "second_order"
 wfc_extrapolation = "second_order"
/
&CELL
  cell_dynamics  = 'damp-w',
  press = 0.0
  wmass = 0.02
/


But the calculation is not conversed and oscillate. The system has only five atoms 
and simple P4mm perovskite structure. 
I had change wmass as default value, but the convergence is not achieved.
Is it too hard to converse to set  forc_conv_thr = 1.0D-4 in VC-relax calculation ? 
( I want to get severe internal atomic coordinate, and forc_conv_thr=1.0D-3 is not 
sufficient.) Simple atomic internal relaxation, I can get converged result. 


The stress and total force of output file is as follow.

stress values ,,

    entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.13
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -2.09
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -1.17
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.60
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.07
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.37
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.84
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.95
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    1.07
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    1.22
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    1.36
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    1.47
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    1.55
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.96
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.65
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.39
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.20
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=    0.04
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.08
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.13
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.13
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.63
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -0.89
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -1.05
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -1.04
     entering subroutine stress ...
          total   stress  (Ry/bohr**3)                   (kbar)     P=   -1.13


and  The total force, 

     Total force =     0.000512     Total SCF correction =     0.000057
     Total force =     0.000499     Total SCF correction =     0.000063
     Total force =     0.000472     Total SCF correction =     0.000024
     Total force =     0.000411     Total SCF correction =     0.000022
     Total force =     0.000385     Total SCF correction =     0.000053
     Total force =     0.000527     Total SCF correction =     0.000012
     Total force =     0.000487     Total SCF correction =     0.000188
     Total force =     0.000572     Total SCF correction =     0.000010
     Total force =     0.000537     Total SCF correction =     0.000016
     Total force =     0.000484     Total SCF correction =     0.000016
     Total force =     0.000440     Total SCF correction =     0.000007
     Total force =     0.000407     Total SCF correction =     0.000017
     Total force =     0.000369     Total SCF correction =     0.000016
     Total force =     0.000391     Total SCF correction =     0.000045
     Total force =     0.000552     Total SCF correction =     0.000015
     Total force =     0.000569     Total SCF correction =     0.000130
     Total force =     0.000683     Total SCF correction =     0.000026
     Total force =     0.000623     Total SCF correction =     0.000025
     Total force =     0.000544     Total SCF correction =     0.000020
     Total force =     0.000404     Total SCF correction =     0.000015
     Total force =     0.000280     Total SCF correction =     0.000028
     Total force =     0.000219     Total SCF correction =     0.000011
     Total force =     0.000348     Total SCF correction =     0.000039
     Total force =     0.000552     Total SCF correction =     0.000015
     Total force =     0.000688     Total SCF correction =     0.000019
     Total force =     0.000741     Total SCF correction =     0.000013
     Total force =     0.000723     Total SCF correction =     0.000013
     Total force =     0.000638     Total SCF correction =     0.000018
     Total force =     0.000504     Total SCF correction =     0.000017
     Total force =     0.000368     Total SCF correction =     0.000029
     Total force =     0.000256     Total SCF correction =     0.000020
     Total force =     0.001173     Total SCF correction =     0.000016
     Total force =     0.001841     Total SCF correction =     0.000271
     Total force =     0.001924     Total SCF correction =     0.000220
     Total force =     0.002328     Total SCF correction =     0.000057
     Total force =     0.002448     Total SCF correction =     0.000019
     Total force =     0.002318     Total SCF correction =     0.000016
     Total force =     0.002004     Total SCF correction =     0.000018
     Total force =     0.001547     Total SCF correction =     0.000022
     Total force =     0.001029     Total SCF correction =     0.000026
     Total force =     0.000669     Total SCF correction =     0.000015
     Total force =     0.002834     Total SCF correction =     0.000206
     Total force =     0.003057     Total SCF correction =     0.000170
     Total force =     0.001864     Total SCF correction =     0.000273
     Total force =     0.001107     Total SCF correction =     0.000101
     Total force =     0.000870     Total SCF correction =     0.000021
     Total force =     0.000355     Total SCF correction =     0.000068
     Total force =     0.000613     Total SCF correction =     0.000114
     Total force =     0.000484     Total SCF correction =     0.000038
     Total force =     0.000338     Total SCF correction =     0.000180
     Total force =     0.000372     Total SCF correction =     0.000125
     Total force =     0.000460     Total SCF correction =     0.000028
     Total force =     0.000482     Total SCF correction =     0.000014
     Total force =     0.000528     Total SCF correction =     0.000018
     Total force =     0.000652     Total SCF correction =     0.000008
     Total force =     0.000729     Total SCF correction =     0.000017
     Total force =     0.000740     Total SCF correction =     0.000013
     Total force =     0.000684     Total SCF correction =     0.000005
     Total force =     0.000573     Total SCF correction =     0.000005
     Total force =     0.000446     Total SCF correction =     0.000012
     Total force =     0.000369     Total SCF correction =     0.000010
     Total force =     0.000408     Total SCF correction =     0.000005
     Total force =     0.000602     Total SCF correction =     0.000044
     Total force =     0.000897     Total SCF correction =     0.000015
     Total force =     0.001145     Total SCF correction =     0.000020
     Total force =     0.001247     Total SCF correction =     0.000004
     Total force =     0.001348     Total SCF correction =     0.000050

Sincerely.


----
Yukihiro Okuno  okunoyukihiro2000 at yahoo.co.jp


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