[Pw_forum] convergence of sigma 5 GB
Ravi Kiran
ravikirans.87 at gmail.com
Wed Oct 8 18:24:16 CEST 2014
Dear Dr.Nicola Marzari,
Thank You very much for your kind reply. I am changed my system and
electron parameters according to your kind suggestions. I have few
questions regarding the convergence of the grain boundary. When the grain
boundary converged the magnetic moment per site of each atom has become
zero and in some cases negative.Does this mean the system has lost
magnetism? .Also
I have checked the converged structure, there is the separation at the
grain boundary.How can I reduce the forces at grain boundary and how can I
keep the GB stable without separation?
On 6 October 2014 12:22, Nicola Marzari <nicola.marzari at epfl.ch> wrote:
>
>
> also, read this:
> http://theossrv1.epfl.ch/Main/ElectronicTemperature
>
> nicola
>
> -------- Original Message --------
> Subject: Re: [Pw_forum] convergence of sigma 5 GB
> Date: Mon, 06 Oct 2014 20:12:51 +0200
> From: Nicola Marzari <nicola.marzari at epfl.ch>
> Organization: École Polytechnique Fédérale de Lausanne
> To: PWSCF Forum <pw_forum at pwscf.org>
>
>
>
> Provided your cell looks good in xcrysden (i.e. no errors in using an
> odd unphysical structure) I would start reducing the beta mixing to 0.2,
> or 0.1, or 0.05 - see if any is sufficient to converge, and if so, which
> is faster. Try using some of the more sophisticated mixing schemes.
>
> Before doing that, note that your pseudopotential is ultrasoft, so
> you need to have an ecutrho between 6 and 12 times larger than
> ecutwfc (ultrasoft pseudopotentials allow for smoother wavefunctions,
> but the charge density is what it is - it can't be made smoother.
> so the usual relation ecutrho=4*ecutwfc, that is correct for a
> rho=|wfc|^2, breaks if the wfc is smoother, and the real rho is
> reproduced by |wfv|^2 + augmentation charges, as it happens in ultrasoft
> pseudos).
>
> Last, given that your unit cell is much longer around z, you should
> sample with a 4 4 2 mesh, not a 4 4 4. Maybe a 2 2 1 mesh would
> be good enough to get things started, and then you increase it at the
> end for the last iterations around the converged geometry.
>
> Note also that typically a 1 1 1 shift (i.e. 2 2 1 1 1 1, or
> 4 4 2 1 1 1) gives better sampling earlier - but something you could
> test in a unit cell of 4 atoms only, with one atom displaced by 5-10%:
> check how the forces converges to the true value as you increase the
> sampling using n n n 0 0 0 or n n n 1 1 1 meshes.
>
> nicola
>
>
> On 06/10/2014 19:52, Ravi Kiran wrote:
>
>> Dear Quantum espresso users,
>>
>> I am looking to study the properties of sigma 5 grain boundary with 80
>> atoms.I am using scf calculations for initial convergence. I am using
>> the following script. The problem is that the values dont converge even
>> after 100 iterations .Can anyone please tell me how can I converge the
>> total energy in order to obtain relaxed atomic coordinates.
>> &control
>> calculation='relax',
>> restart_mode='restart',
>> prefix='Ni',
>> tprnfor =.t.,
>> pseudo_dir = '/psuedo/',
>> outdir='/psuedo/tmp',
>> /
>> &SYSTEM
>> nat =80,
>> ntyp = 1,
>> degauss = 0.02,
>> nspin = 2,
>> starting_magnetization = 0.62,
>> ecutwfc = 24,
>> ibrav = 0,
>> occupations = 'smearing',
>> smearing = 'mv',
>> /
>> &ELECTRONS
>> conv_thr = 1e-6,
>> mixing_beta = 0.3,
>> /
>> &IONS
>> /
>> &CELL
>> /
>>
>> ATOMIC_SPECIES
>> Ni 58.69d0 Ni.pz-nd-rrkjus.UPF
>> K_POINTS automatic
>> 4 4 4 0 0 0
>> ATOMIC_POSITIONS
>> Ni 0.000000 0.000000 0.500000
>> Ni 0.000000 0.000000 0.250000
>> Ni 0.400000 0.200000 0.500000
>> Ni 0.400000 0.200000 0.250000
>> Ni 0.200000 0.600000 0.500000
>> Ni 0.200000 0.600000 0.250000
>> Ni 0.800000 0.400000 0.500000
>> Ni 0.800000 0.400000 0.250000
>> Ni 0.600000 0.800000 0.500000
>> Ni 0.600000 0.800000 0.250000
>> Ni 0.100000 0.300000 0.500000
>> Ni 0.100000 0.300000 0.250000
>> Ni 0.700000 0.100000 0.500000
>> Ni 0.700000 0.100000 0.250000
>> Ni 0.500000 0.500000 0.500000
>> Ni 0.500000 0.500000 0.250000
>> Ni 0.300000 0.900000 0.500000
>> Ni 0.300000 0.900000 0.250000
>> Ni 0.900000 0.700000 0.500000
>> Ni 0.900000 0.700000 0.250000
>> Ni 0.500000 0.000000 0.375000
>> Ni 0.500000 0.000000 0.125000
>> Ni 0.300000 0.400000 0.375000
>> Ni 0.300000 0.400000 0.125000
>> Ni 0.100000 0.800000 0.375000
>> Ni 0.100000 0.800000 0.125000
>> Ni 0.900000 0.200000 0.375000
>> Ni 0.900000 0.200000 0.125000
>> Ni 0.700000 0.600000 0.375000
>> Ni 0.700000 0.600000 0.125000
>> Ni 0.200000 0.100000 0.375000
>> Ni 0.200000 0.100000 0.125000
>> Ni 0.000000 0.500000 0.375000
>> Ni 0.000000 0.500000 0.125000
>> Ni 0.600000 0.300000 0.375000
>> Ni 0.600000 0.300000 0.125000
>> Ni 0.400000 0.700000 0.375000
>> Ni 0.400000 0.700000 0.125000
>> Ni 0.800000 0.900000 0.375000
>> Ni 0.800000 0.900000 0.125000
>> Ni 0.000000 0.000000 0.750000
>> Ni 0.000000 0.000000 1.000000
>> Ni 0.600000 0.200000 0.750000
>> Ni 0.600000 0.200000 1.000000
>> Ni 0.200000 0.400000 0.750000
>> Ni 0.200000 0.400000 1.000000
>> Ni 0.800000 0.600000 0.750000
>> Ni 0.800000 0.600000 1.000000
>> Ni 0.400000 0.800000 0.750000
>> Ni 0.400000 0.800000 1.000000
>> Ni 0.300000 0.100000 0.750000
>> Ni 0.300000 0.100000 1.000000
>> Ni 0.900000 0.300000 0.750000
>> Ni 0.900000 0.300000 1.000000
>> Ni 0.500000 0.500000 0.750000
>> Ni 0.500000 0.500000 1.000000
>> Ni 0.100000 0.700000 0.750000
>> Ni 0.100000 0.700000 1.000000
>> Ni 0.700000 0.900000 0.750000
>> Ni 0.700000 0.900000 1.000000
>> Ni 0.800000 0.100000 0.625000
>> Ni 0.800000 0.100000 0.875000
>> Ni 0.400000 0.300000 0.625000
>> Ni 0.400000 0.300000 0.875000
>> Ni 0.000000 0.500000 0.625000
>> Ni 0.000000 0.500000 0.875000
>> Ni 0.600000 0.700000 0.625000
>> Ni 0.600000 0.700000 0.875000
>> Ni 0.200000 0.900000 0.625000
>> Ni 0.200000 0.900000 0.875000
>> Ni 0.500000 0.000000 0.625000
>> Ni 0.500000 0.000000 0.875000
>> Ni 0.100000 0.200000 0.625000
>> Ni 0.100000 0.200000 0.875000
>> Ni 0.700000 0.400000 0.625000
>> Ni 0.700000 0.400000 0.875000
>> Ni 0.300000 0.600000 0.625000
>> Ni 0.300000 0.600000 0.875000
>> Ni 0.900000 0.800000 0.625000
>> Ni 0.900000 0.800000 0.875000
>> CELL_PARAMETERS
>> 14.87 0 0
>> 0 14.87 0
>> 0 0 26.60
>>
>>
>>
>> --
>> Thanks
>> Ravi
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>>
> --
>
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
>
> --
> ---------------------------------------------------------------------
> Prof Nicola Marzari Department of Materials Science and Engineering
> 13-5066 MIT 77 Massachusetts Avenue Cambridge MA 02139-4307 USA
> tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu
>
>
>
> --
>
> ----------------------------------------------------------------------
> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
>
--
Thanks
Ravi
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