[Pw_forum] Re: Problem with vc -relax

[shruba at gmail.com]

Thanks a lot Cesar.
  That works,  still I am facing a problem because the single point optimum
lattice parameter and the vc-relax optimum one is quite different
around 0.1angstrom, I tried changing cell _factor and wmass parameter
but those are
not affecting much on optimum lattice paraneter.
         if anybody can provide me any hints or  suggest some references on
this topic then it will be real helpful.
thanks in advance
                         shruba ganaygopadhy


shruba gangopadhyay
graduate student
department of chemistry
university of central florida
orlando, FL-32826



On 6/18/07, cesards at msi.umn.edu <cesards at msi.umn.edu> wrote:
>
> Dear Shruba,
>
>
> I notice that your input doe not contains the varables "dt" in &CONTROL
> namelist (dt = 80.0 is recommended for start) and "wmass" in &CELL
> namelist (wmass =  0.001 , for example). If get large negative stresses in
> the first MD step, try to reduce celldm(1).
>
> It is normal for the cell volume to oscilate. Things are going wrong only
> if the amplitude of oscilations are increasing.
>
>
> Yours,
>
>
> Cesar R.S. da Silva
>
>
>
>
> > ------=_Part_75233_9601271.1182103000930
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> > Content-Transfer-Encoding: 7bit
> > Content-Disposition: inline
> >
> > Hi all,
> >      I was trying to run vc-relax calculation for srfeo3 (
> > antiferromagnetic
> > mettalic ) system,  the problem I was facing for a unit cell it is
> running
> > for 3-4 days in processor , where as a single point 'scf' calculation is
> > taking only 5 minutes, the scf calculation is giving very nice agreement
> > with experimental data , but for vc -relax  i checked the cell volume
> was
> > decresing first then it started exapnding after a certain point, this is
> > my
> > input file . If any one can help me in this matter that will be really
> > great
> > help, I am using same cutoff and other parameters required for scf
> >
> > &CONTROL
> >
> > calculation = 'vc-relax',
> >
> > restart_mode = 'from_scratch',
> >
> > tstress = .TRUE.,
> >
> > tprnfor = .TRUE.,
> >
> > prefix = 'relax',
> >
> > pseudo_dir = '/............./',
> >
> > outdir='/................../'
> >
> > /
> >
> > &SYSTEM
> >
> > ibrav = 1,
> >
> > celldm(1) = 7.3
> >
> > nat =5,
> >
> > ntyp =3,
> >
> > ecutwfc = 45,
> >
> > ecutrho = 360,
> >
> > nspin=2,
> >
> > nelec=44
> >
> > nelup=26,
> >
> > neldw=18,
> >
> > nbnd=52,
> >
> > occupations = 'smearing',
> >
> > smearing ='marzari-vanderbilt',
> >
> > degauss=0.03,
> >
> > qcutz=150., q2sigma=2.0,ecfixed=10.0
> >
> > /
> >
> > &ELECTRONS
> >
> > electron_maxstep =200,
> >
> > emass =1000.d0,
> >
> > emass_cutoff = 4.d0,
> >
> > orthogonalization = 'Gram-Schmidt',
> >
> > startingwfc ='atomic',
> >
> > n_inner = 8,
> >
> > tcg = .TRUE.,
> >
> > passop=0.3,
> >
> > maxiter = 250,
> >
> > conv_thr=1.d-6,
> >
> > /
> >
> > &IONS
> >
> > ion_dynamics = 'damp',
> >
> > ion_damping = 0.,
> >
> > ion_positions = 'from_input',
> >
> > ion_temperature = 'not_controlled',
> >
> > /
> >
> > &CELL
> >
> > cell_dynamics = 'damp-w'
> >
> > /
> >
> > ATOMIC_SPECIES
> >
> > Fe 55.85 Fe.pbe-sp-van.UPF
> >
> > Sr 87.62 Sr.pbe-nsp-van.UPF
> >
> > O 16.00 O.pbe-van-bm.UPF
> >
> > ATOMIC_POSITIONS
> >
> > Sr 0.000 0.000 0.010
> >
> > Fe 0.500 0.500 0.500
> >
> > O 0.000 0.500 0.500
> >
> > O 0.500 0.500 0.000
> >
> > O 0.500 0.000 0.500
> >
> > K_POINTS {automatic}
> >
> > 8 8 8 1 1 1
> >
> > Thanks in advance , looking forward for your reply
> >                                 shruba
> >
> > --
> > shruba gangopadhyay
> > graduate student
> > department of chemistry
> > university of central florida
> > orlando, FL-32826
> > 'friendship doubles joys and reduces sorrows by half' (Francis Bacon).
> >
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>



-- 
shruba gangopadhyay
graduate student
department of chemistry
university of central florida
orlando, FL-32826
'friendship doubles joys and reduces sorrows by half' (Francis Bacon).
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20070620/89bca397/attachment.html>