[Pw_forum] SCF run not converging

[Paolo Giannozzi]

On Wed, Dec 14, 2016 at 3:00 PM, sayan chaudhuri <csayan895 at gmail.com> wrote:

>    How to get rid of the small unit cell problem?

what is the "small unit cell problem"?

Paolo
>    When it is a pure system, Wycoff positions with Atomic positions card set
> at alat works. So, is there any definite procedure to give the position of
> the atoms in the system when I am doping in the system?
>
>  Thanking you,
>         Sayan Chaudhuri
>
> On Fri, Dec 9, 2016 at 7:07 PM, Lorenzo Paulatto
> <lorenzo.paulatto at impmc.upmc.fr> wrote:
>>
>> It may be difficult to converge LDA+U calculations in general, starting
>> with
>> initial magnetizations that aren't absurd may help
>>
>> hth
>>
>> On Friday, December 9, 2016 5:29:01 PM CET Максим Арсентьев wrote:
>> > Dear Lorenzo,
>> >
>> > I have the same problem - cannot achieve SCF convergence. I use higher
>> > ecutwfc = 39.0, ecutrho = 300 but not coverging.
>> >
>> > Regards, Maxim Arsentev.
>> >
>> > 2016-12-09 12:52 GMT+04:00 Lorenzo Paulatto
>> > <lorenzo.paulatto at impmc.upmc.fr>
>> > > Dear Sayan,
>> > > it looks to me like your unit cell is too small, the atoms are all
>> > > crumped
>> > > together.  Please note that celldm(1) is specified in bohr atomic
>> > > units.
>> > >
>> > > Also:
>> > > 1. a cutoff of 30Ry is probably very small for BHS pseudopotentials
>> > > 2. ecutrho=default (4*ecutwfc ) is probably not enough for all the
>> > > ultrasoft
>> > > pseudopotentials you are using
>> > >
>> > > I would recommend you first spend some time reproducin the
>> > > single-element
>> > > metal, and once you can correctly reproduce geometry, band structure,
>> > > physical
>> > > properties, you move to simulating the alloy.
>> > >
>> > > HTH
>> > >
>> > > On Friday, December 9, 2016 1:59:44 PM CET sayan chaudhuri wrote:
>> > > > Hi,
>> > > >
>> > > >    I am running QE self - consistently for my heusler alloy(Fe2TiSn)
>> > > >
>> > > > system, where 25% of Sn were replaced by Sb. But after 800
>> > > > iterations
>> > > > and
>> > > > almost 3 hours of running also still it is not converged.
>> > > > The code I am using is added bellow. Please tell me what is the
>> > > > source
>> > > > of
>> > > > error.
>> > > >
>> > > > Thanking you,
>> > > >
>> > > >    Sayan Chaudhuri
>> > > >
>> > > > *&control    prefix='fts',    calculation  = 'scf',    verbosity =
>> > > > 'low',    pseudo_dir   = '/home/ltp/Desktop/espresso-5.4.0/pseudo',
>> > > > outdir       = './tmp', / &system    ibrav=2    celldm(1)=11.43,
>> > > > nat=16,    ntyp=4,        nspin=2,    ecutwfc=30.0,
>> > > > starting_magnetization(1) =  0.0,    starting_magnetization(2) =
>> > > > 0.0,
>> > > > starting_magnetization(3) =  0.5,    starting_magnetization(3) =
>> > > > 0.0,
>> > > > occupations='tetrahedra',    / &electrons    electron_maxstep =
>> > > > 3000,
>> > > > diagonalization = 'david',    mixing_mode = 'plain',    conv_thr =
>> > > > 1e-8,
>> > > > mixing_beta=0.1, /ATOMIC_SPECIES  Sb   121.76   Sb.pz-bhs.UPF  Sn
>> > > > 118.71   Sn.pz-dn-rrkjus_psl.0.2.UPF  Fe   55.845
>> > > > Fe.pz-sp-van_ak.UPF
>> > > > Ti   47.867   Ti.pz-sp-van.UPFATOMIC_POSITIONS {crystal} Sb
>> > > > 0.000000000         0.000000000         0.000000000 Sn
>> > > > 0.000000000         0.500000000         0.500000000 Sn
>> > > > 0.500000000         0.000000000         0.500000000 Sb
>> > > > 0.500000000         0.500000000         0.000000000 Fe
>> > > > 0.250000000         0.250000000         0.250000000 Fe
>> > > > 0.750000000         0.750000000         0.750000000 Fe
>> > > > 0.750000000         0.750000000         0.250000000 Fe
>> > > > 0.250000000         0.250000000         0.750000000 Fe
>> > > > 0.750000000         0.250000000         0.750000000 Fe
>> > > > 0.250000000         0.750000000         0.250000000 Fe
>> > > > 0.250000000         0.750000000         0.750000000 Fe
>> > > > 0.750000000         0.250000000         0.250000000 Ti
>> > > > 0.500000000         0.500000000         0.500000000 Ti
>> > > > 0.500000000         0.000000000         0.000000000 Ti
>> > > > 0.000000000         0.500000000         0.000000000 Ti
>> > > > 0.000000000         0.000000000         0.500000000 K_POINTS
>> > > > {automatic}
>> > > > 2 2 2 0 0 0*
>> > >
>> > > --
>> > > Dr. Lorenzo Paulatto
>> > > IdR @ IMPMC -- CNRS & Université Paris 6
>> > > phone: +33 (0)1 44275 084 / skype: paulatz
>> > > www:   http://www-int.impmc.upmc.fr/~paulatto/
>> > > mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris
>> > > Cédex 05
>> > >
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>>
>>
>> --
>> Dr. Lorenzo Paulatto
>> IdR @ IMPMC -- CNRS & Université Paris 6
>> phone: +33 (0)1 44275 084 / skype: paulatz
>> www:   http://www-int.impmc.upmc.fr/~paulatto/
>> mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
>>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222