[Pw_forum] vc-relax convergence
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Mon Aug 7 13:18:50 CEST 2017
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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>>
>> 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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********************************************************
- 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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