[Pw_forum] The stress in the output of the scf.

[Axel Kohlmeyer]

On Sat, 16 Sep 2006, lyw1983 wrote:

> Dear all,
>    when I test the ecutwfc for CrO2, I found that the stress at the end of the output file change largely with differenr ecutwfc values, I choose the ultrasoft pseudopotential for Cr and O, the pseudopotential as follow:
>   Cr  Cr.pbe-sp-van.UPF
>   O   O.pbe-rrkjus.UPF
>    what can cause this result and who can tell me?

hi,

this behavior is normal. the stress tensor is a quantity that 
converges rather slowly with the wavefunction cutoff.

please check the mailing list archives.

axel.


>    The input file as below:
> 
> 
> . ../../environment/environment_2
> for ecut in 30 35 40 45 50  
> do
>  rm -rf $TMP_DIR/*
> 
> cat > cro2.scf.in << EOF
>  &control
>     calculation = 'scf'
>     restart_mode='from_scratch',
>     prefix='cro2',
>     tstress = .true.
>     tprnfor = .true.
>     pseudo_dir = '$PSEUDO_DIR/',
>     outdir='$TMP_DIR/'
>  /
>  &system
>        ibrav=  6, celldm(1) = 8.3544825, celldm(3) =0.65957928, nat= 6, ntyp= 2,
>     nspin = 2,  starting_magnetization6(1)=0.7,starting_magnetization(2)=0.0,ecutwfc =$ecut,ecutrho=400,
>     occupations = 'smearing',smearing = 'methfessel-paxton',degauss = 0.03
> 
>  /
>  &electrons
>       mixing_beta = 0.7
>     conv_thr =  1.0d-8
>  /
> ATOMIC_SPECIES
>  Cr  52.000  Cr.pbe-sp-van.UPF 
>  O   15.999  O.pbe-rrkjus.UPF
> ATOMIC_POSITIONS {crystal}
> Cr 0.000000  0.000000  0.000000
> Cr 0.500000  0.500000  0.500000
> O  0.301000  0.301000  0.000000
> O  0.699000  0.699000  0.000000
> O  0.199000  0.801000  0.500000
> O  0.801000  0.199000  0.500000
> K_POINTS {automatic}
> 4 4 6 0 0 0
> 
> EOF
> 
> $PARA_PREFIX /home/pwscf/pwscf_215/bin/pw.x $PARA_POSTFIX < cro2.scf.in >cro2.scf.out_$ecut
> done
> 

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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