[Pw_forum] vc-relax convergence

Manu Hegde mhegde at uwaterloo.ca
Mon Aug 7 17:07:41 CEST 2017


Dear Giuseppe,
Thank you very much!
Manu

On Mon, Aug 7, 2017 at 7:18 AM, Giuseppe Mattioli <
giuseppe.mattioli at ism.cnr.it> wrote:

>
> Dear Manu
>
> > Is EXX-ACE implemented in QE 6.1v by default or do I have to compile it
> > separately?.
>
> Honestly, I would not give it for granted! Put the ACE flag in the
> make.inc file, it should not harm. :-)
>
> > If I am not using HSE , do I have to use LDA level theory for TiO2 with
> > defects?.
>
> Note that there are tons of papers on TiO2 defects. If you do not want
> to use EXX, then you can try with DFT+U(Ti,O). I've used it here
>
> J. Phys. Chem. C 2010, 114, 21694
> J. Phys. Chem. C 2014, 118, 29928
>
> with apparently good results. I would suggest these values or
> something around:
>
>      lda_plus_u=.true.,
>      Hubbard_U(1)=3.2, <----Ti
>      Hubbard_U(2)=2.0, <----O
>
> HTH
> Giuseppe
>
> Quoting Manu Hegde <mhegde at uwaterloo.ca>:
>
> > Hi Stefano and Giuseppe,
> >
> > Thanks for your feedback.
> >
> > I just wanted to try 48 atom supercell initially and see how it goes (to
> > save computation time as well). I will try 108 atom supercell definitely.
> >
> > Is EXX-ACE implemented in QE 6.1v by default or do I have to compile it
> > separately?. I will try to run it (if our busy HPC facility permits!).
> >
> > If I am not using HSE , do I have to use LDA level theory for TiO2 with
> > defects?.
> >
> > Thanks
> > Manu
> > (University of Waterloo)
> >
> > On Sun, Aug 6, 2017 at 6:08 PM, Giuseppe Mattioli <
> > giuseppe.mattioli at ism.cnr.it> wrote:
> >
> >>
> >> On the top of Stefano's answer, I would add that in a 48 atom
> >> supercell the interaction between the relaxation sphere of an oxygen
> >> vacancy and its periodic images along the 100 or 010 directions is too
> >> strong and can lead to an improper description of the electronic
> >> properties of the defect that can not be considered as an "isolated
> >> defect" anymore. I suggest that you use at least a 3x3x1 108-atom
> >> supercell. With the new EXX-ACE implementation you may probably afford
> >> an HSE calculation, otherwise remember also that the small-polaron
> >> character of excess electrons in TiO2 such as those induced by the O
> >> vacancy is not at all well described at the GGA level of theory.
> >> HTH
> >> Giuseppe
> >>
> >> stefano de gironcoli <degironc at sissa.it> ha scritto:
> >>
> >> > yes
> >> > start from the perfect relaxed geometry (as obtained from vc-relax)
> >> > remove an atom and relax the internal structure.
> >> > at the end also perform a vc-relaxation (from the fixed-cell relaxed
> >> > geometry)
> >> > stefano
> >> >
> >> > On 06/08/2017 17:33, Manu Hegde wrote:
> >> >> Hello Stephano,
> >> >> Thanks for your reply. Just to double check what you meant before
> >> >> starting the calculations, you mean take the equilibrium values
> >> >> from the vc-relax calculation (perfect cell,  only co-ordinates)
> >> >> and do the 'relax' calculation with defect?.
> >> >> Manu
> >> >> (University of Waterloo).
> >> >>
> >> >>
> >> >> On Sun, Aug 6, 2017 at 11:15 AM, stefano de gironcoli
> >> >> <degironc at sissa.it <mailto:degironc at sissa.it>> wrote:
> >> >>
> >> >>    does the energy (enthalpy) decreases as the vc-relaxation
> >> >>    progresses ?
> >> >>    The local structure around the defect may be quite different. It
> >> >>    may just take long.
> >> >>
> >> >>    I would start by performing a fixed cell relaxation with the cell
> >> >>    parameters fixed at the undefected equilibrium values. And only
> >> >>    after that I would start the vc-relax calculation from the so
> >> >>    relaxed configuration to evaluate the vacancy formation volume.
> >> >>    The local arrangement around the defect should be already more or
> >> >>    less ok (if the supercell is large enough).
> >> >>
> >> >>    HTH
> >> >>    stefano
> >> >>
> >> >>
> >> >>
> >> >>    On 06/08/2017 16:40, Manu Hegde wrote:
> >> >>>    Hello,
> >> >>>
> >> >>>    I am trying to optimize anatase TiO2 supercell with 48 atoms. The
> >> >>>    supercell converges in 15 BFGS cycles for a perfect cell. But
> >> >>>    when I introduce defect (by removing one of the oxygen atom), the
> >> >>>    vc-relax is not t all converging. I am using the same parameters
> >> >>>    in both the cases. Can anyone give some feedback on this.?.  Here
> >> >>>    is my input,
> >> >>>
> >> >>>
> >> >>>    &control
> >> >>>     calculation = 'vc-relax' ,
> >> >>>    restart_mode = 'from_scratch' ,
> >> >>>    outdir = '/work/mhegde/tmp_tiodef/',
> >> >>>    pseudo_dir = '/home/mhegde/tio_project/def_tio/',
> >> >>>    prefix = 'tioan',
> >> >>>     verbosity = 'high',
> >> >>>
> >> >>>     /
> >> >>>     &system
> >> >>>     ibrav = 0,
> >> >>>     nat = 47,
> >> >>>      ntyp = 2,
> >> >>>     ecutwfc =40,
> >> >>>     ecutrho=400,
> >> >>>     occupations='smearing',
> >> >>>    degauss=0.003
> >> >>>
> >> >>>     /
> >> >>>     &electrons
> >> >>>    conv_thr = 1.D-6,
> >> >>>    mixing_beta=0.1
> >> >>>    /
> >> >>>    &ions
> >> >>>    ion_dynamics='bfgs'
> >> >>>
> >> >>>    /
> >> >>>    &cell
> >> >>>    cell_dynamics='bfgs'
> >> >>>
> >> >>>    /
> >> >>>    ATOMIC_SPECIES
> >> >>>       Ti  47.867000  Ti.pw91-nsp-van.UPF
> >> >>>       O   15.99900 O.pw91-van_ak.UPF
> >> >>>
> >> >>>    ATOMIC_POSITIONS angstrom
> >> >>>    Ti 0.00000000       2.84182500 1.20970000
> >> >>>    Ti 1.89455000       2.84182500 3.62910000
> >> >>>    O  0.00000000       0.94727500 1.99939216
> >> >>>    O  0.00000000       2.84182500 4.41879216
> >> >>>    O  1.89455000       0.94727500 2.83940784
> >> >>>    Ti  -1.89455000       0.94727500  -3.62910000
> >> >>>    Ti 0.00000000       0.94727500  -1.20970000
> >> >>>    O -1.89455000      -0.94727500  -2.83940784
> >> >>>    O -1.89455000       0.94727500  -0.42000784
> >> >>>    O  0.00000000      -0.94727500  -1.99939216
> >> >>>    O  0.00000000       0.94727500  -4.41879216
> >> >>>    Ti 0.00000000      -0.94727500 1.20970000
> >> >>>    Ti 1.89455000      -0.94727500 3.62910000
> >> >>>    O  0.00000000      -2.84182500 1.99939216
> >> >>>    O  0.00000000      -0.94727500 4.41879216
> >> >>>    O  1.89455000      -2.84182500 2.83940784
> >> >>>    O  1.89455000      -0.94727500 0.42000784
> >> >>>    Ti  -1.89455000      -2.84182500  -3.62910000
> >> >>>    Ti 0.00000000      -2.84182500  -1.20970000
> >> >>>    O -1.89455000       2.84182500  -2.83940784
> >> >>>    O -1.89455000      -2.84182500  -0.42000784
> >> >>>    O  0.00000000       2.84182500  -1.99939216
> >> >>>    O  0.00000000      -2.84182500  -4.41879216
> >> >>>    Ti  -3.78910000       2.84182500 1.20970000
> >> >>>    Ti  -1.89455000       2.84182500 3.62910000
> >> >>>    O -3.78910000       0.94727500 1.99939216
> >> >>>    O -3.78910000       2.84182500 4.41879216
> >> >>>    O -1.89455000       0.94727500 2.83940784
> >> >>>    O -1.89455000       2.84182500 0.42000784
> >> >>>    Ti 1.89455000       0.94727500  -3.62910000
> >> >>>    Ti  -3.78910000       0.94727500  -1.20970000
> >> >>>    O  1.89455000      -0.94727500  -2.83940784
> >> >>>    O  1.89455000       0.94727500  -0.42000784
> >> >>>    O -3.78910000      -0.94727500  -1.99939216
> >> >>>    O -3.78910000       0.94727500  -4.41879216
> >> >>>    Ti  -3.78910000      -0.94727500 1.20970000
> >> >>>    Ti  -1.89455000      -0.94727500 3.62910000
> >> >>>    O -3.78910000      -2.84182500 1.99939216
> >> >>>    O -3.78910000      -0.94727500 4.41879216
> >> >>>    O -1.89455000      -2.84182500 2.83940784
> >> >>>    O -1.89455000      -0.94727500 0.42000784
> >> >>>    Ti 1.89455000      -2.84182500  -3.62910000
> >> >>>    Ti  -3.78910000      -2.84182500  -1.20970000
> >> >>>    O  1.89455000       2.84182500  -2.83940784
> >> >>>    O  1.89455000      -2.84182500  -0.42000784
> >> >>>    O -3.78910000       2.84182500  -1.99939216
> >> >>>    O -3.78910000      -2.84182500  -4.41879216
> >> >>>
> >> >>>    K_POINTS {automatic}
> >> >>>
> >> >>>     2 2 2   0 0 0
> >> >>>
> >> >>>    CELL_PARAMETERS angstrom
> >> >>>
> >> >>>     7.57820000   0.00000000       0.00000000
> >> >>>     0.00000000   7.57820000       0.00000000
> >> >>>     0.00000000   0.00000000       9.67760000
> >> >>>
> >> >>>    Thanks,
> >> >>>    Manu
> >> >>>    (University of Waterloo)
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>>    _______________________________________________
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> >> >>
> >> >>
> >> >>
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> >> >>
> >> >>
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> >>
> >>     Giuseppe Mattioli
> >>     CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> >>     v. Salaria Km 29,300 - C.P. 10
> >>     I 00015 - Monterotondo Stazione (RM)
> >>     Tel + 39 06 90672836 - Fax +39 06 90672316
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> --
> ********************************************************
> - Article premier - Les hommes naissent et demeurent
> libres et égaux en droits. Les distinctions sociales
> ne peuvent être fondées que sur l'utilité commune
> - Article 2 - Le but de toute association politique
> est la conservation des droits naturels et
> imprescriptibles de l'homme. Ces droits sont la liberté,
> la propriété, la sûreté et la résistance à l'oppression.
> ********************************************************
>
>     Giuseppe Mattioli
>     CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
>     v. Salaria Km 29,300 - C.P. 10
>     I 00015 - Monterotondo Stazione (RM)
>     Tel + 39 06 90672836 - Fax +39 06 90672316
>     E-mail: <giuseppe.mattioli at ism.cnr.it>
>     http://www.ism.cnr.it/en/staff/giuseppe-mattioli/
>     ResearcherID: F-6308-2012
>
>
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