[Pw_forum] converge problem in calculating the vacancy on TiO2 surfaces
vega lew
quantumdft at gmail.com
Sun Mar 1 13:09:06 CET 2009
Dear friend,
I found there is few supporting materials decribing what the exact meaning
for mixing_beta. do you think the following paragraph from the manual of
Materials Studio is suitable for this parameters?
------------------------------------------------
SCF tab
Electronic minimizer: Specify the electronic minimization method to be used
for the SCF calculation. Two options are available, Density Mixing and All
Bands/EDFT.
Tip. The Density Mixing option is recommended, particularly for variable
occupancy calculations. The All Bands/EDFT method is usually slower and
requires more memory. However, the EDFT scheme is recommended for metallic
systems where converging electronic structure using Density Mixing option
proves problematic.
Charge: Specify the amplitude for charge density mixing (i.e., the amplitude
of the output charge density to mix with the input charge density to obtain
input for the next iteration).
Note. This option is enabled only if the Density Mixing minimization method
is selected.
Spin: Specify the amplitude for spin density mixing, i.e. the amplitude of
the output spin density to mix with the input spin density to obtain input
for the next iteration.
Note. This option in enabled only for spin-polarized calculations
using the Density
Mixing minimization method.
-------------------------------------------------
Shoul I consider the mixing_mode option in PWSCF is equal to Density Mixing
option in MS, and value of mixing_bate in PWSCF is equal to the one of Charge
in MS?
Do you think I should swich on the boardening by 'occupations', 'degauss'
and 'smearing' command in PWSCF?
I also found no detail description for this three options.
do you think the following text suitable for the three command in PWSCF?
-----------------------------
SCF tab
Smearing: Specify the broadening to be applied to the electronic occupation.
Note. This option is enabled only for variable occupancy calculations.
-----------------------------
If the answer is no, could you please give me some suggestion to
understanding the command and make a better use of it.
thank you so much for reading
best wishes,
vega
On Sun, Mar 1, 2009 at 7:44 PM, vega lew <quantumdft at gmail.com> wrote:
> Dear APSI
>
> thank you for you suggestions to me.
>
> I will try it ASAP.
>
> vega
>
> On Sun, Mar 1, 2009 at 5:08 PM, Ari Paavo Seitsonen <
> ari.p.seitsonen at iki.fi> wrote:
>
>>
>> Dear Vega,
>>
>> Just my guesses and suggestions: One could try mixing of the density,
>> like
>>
>> &electrons
>> mixing_beta = 0.7
>> /
>>
>> (or a value even smaller than 0.7, or some other parametres for the
>> mixing) since with a defect you might now have defect levels in the band
>> gap, leading to a more difficult a convergence. Eventually one could also
>> switch on the broadening of the occupation numbers, eventually switching it
>> off for the physical/production jobs, but just to check if the problem in
>> convergence comes due to this.
>>
>> And in the original paper the authors discuss spin-polarisation, one
>> might test also this (nspin = 2), with different initial magnetisations
>> [starting_magnetization(xx) = ...] for the atoms surrounding the defect.
>>
>> Greetings,
>>
>> apsi
>>
>>
>> On Sun, 1 Mar 2009, vega lew wrote:
>>
>> Dear all,
>>>
>>> I am planning to calculate the Oxygen vacancy properties of TiO2
>>> surfaces.
>>> The calculation for the ideal surfaces are quite normal and the results
>>> are
>>> in line with the one that literature reported. But, when I tried to
>>> calculate the anatase 101 surface with an Oxygen vacancy (O2c was removed
>>> directly from the stoichiometric Anatase 101as described in J. Phys.
>>> Chem. C
>>> 2007, 111, 16397-16404, I encounter the problem of convergence for SCF
>>> cycle. I tried to add 20% more empty band to the system the problem
>>> still
>>> laid in. How could I overcome the problem?
>>>
>>> my input file was attached at the bottom of the mail
>>>
>>> thank you for reading. Any hints will be appreciated.
>>>
>>> vega
>>>
>>>
>> ...
>>
>>
>>
>>> &SYSTEM
>>> ibrav = 8,
>>> celldm(1) =19.3269,
>>> celldm(2) = 1.1094,
>>> celldm(3) = 1.7450,
>>> nat = 71,
>>> ntyp = 2,
>>> nosym = .true.,
>>> ecutwfc = 30,
>>> ecutrho = 300,
>>> /
>>>
>>> &ELECTRONS
>>>
>>> /
>>>
>>> &IONS
>>> ion_dynamics = 'bfgs',
>>> /
>>>
>>>
>> --
>>
>> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
>> Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/<http://www.iki.fi/%7Eapsi/>
>> IMPMC, CNRS & Université Pierre et Marie Curie
>> Tel: +33-1-4427 7542, Fax: +33-1-4427 3785, GSM: +33-6-6736 3820
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>>
>
>
> --
>
> ==================================================================================
> Vega Lew ( weijia liu)
> PH.D Candidate in Chemical Engineering
> State Key Laboratory of Materials-oriented Chemical Engineering
> College of Chemistry and Chemical Engineering
> Nanjing University of Technology, 210009, Nanjing, Jiangsu, China
>
> ******************************************************************************************************************
> Email: vegalew at gmail.com
> Office: Room A705, Technical Innovation Building, Xinmofan Road 5#,
> Nanjing, Jiangsu, China
> ******************************************************************************************************************
>
>
--
==================================================================================
Vega Lew ( weijia liu)
PH.D Candidate in Chemical Engineering
State Key Laboratory of Materials-oriented Chemical Engineering
College of Chemistry and Chemical Engineering
Nanjing University of Technology, 210009, Nanjing, Jiangsu, China
******************************************************************************************************************
Email: vegalew at gmail.com
Office: Room A705, Technical Innovation Building, Xinmofan Road 5#, Nanjing,
Jiangsu, China
******************************************************************************************************************
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