[Pw_forum] converge problem in calculating the vacancy on TiO2 surfaces
lan haiping
lanhaiping at gmail.com
Sun Mar 1 13:20:58 CET 2009
Hi, Weijia,
In fact, you can have a look at mix_rho.f90 for detailed agorithms used
in QE package for density mixing scheme .
The scheme is just modified Broyden's method for charge density mixing
, please see D.D. Johnson PRB 38, 12807 (1988).
regards,
On Sun, Mar 1, 2009 at 8:09 PM, vega lew <quantumdft at gmail.com> wrote:
> 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?
>
> ------------------------------------------------
>
> Electronic minimizer: Specify the electronic minimization method to be
> used for the SCF calculation. Two options are available, Density Mixingand 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?
>
> -----------------------------
>
> 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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>
>
--
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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