[Pw_forum] Improve convergence, slab and electric field.

[joaquin peralta]

Sorry , my mistake 'again' I wrote bad units I'm using :

1V/nm = 0.0019447 [au] (Input for espresso)
with this the convergence is ok.

When i increase the electric field to  (using previous charge density)

3V/nm = 0.00583431 [au]

The convergence energy present the jumps.
    total energy              =    -261.46819272 Ry
    total energy              =    -261.46815798 Ry
    total energy              =    -261.46816720 Ry
    total energy              =    -261.46260676 Ry
    total energy              =    -261.37365516 Ry
    total energy              =    -261.46820680 Ry
    total energy              =    -261.46821935 Ry
    total energy              =    -261.46807352 Ry
    total energy              =    -261.46825528 Ry
    total energy              =    -261.46820900 Ry
    total energy              =    -261.46803348 Ry

I'm using as reference the paper of Sanchez (Molecular Physics, 102: 9,
1045-1055). In this study they use from 0 to 2 ev/A (this units are right
now)

Any hint I really appreciate it,

Thanks in advance
Joaquin Peralta

On Thu, Sep 2, 2010 at 8:44 AM, Stefano de Gironcoli <degironc at sissa.it>wrote:

> 1 eV/A is a already a Huge electric field...
> how thick is your slab ? how many eV is the potential drop from one side to
> the other ? is that a reasonable situation ?
> stefano
>
>
> Quoting joaquin peralta <jperaltac at gmail.com>:
>
>  Thanks, i obtain more fast convergence for 1V/A, but ...
>>
>> If I use the previous results from 1V/A in order to calculate an increase
>> in
>> the Field i obtain fluctuation in the energy.
>>
>>     total energy              =    -261.46819272 Ry
>>     total energy              =    -261.46815798 Ry
>>     total energy              =    -261.46816720 Ry
>>     total energy              =    -261.46260676 Ry
>>     total energy              =    -261.37365516 Ry
>>     total energy              =    -261.46820680 Ry
>>     total energy              =    -261.46821935 Ry
>>     total energy              =    -261.46807352 Ry
>>     total energy              =    -261.46825528 Ry
>>     total energy              =    -261.46820900 Ry
>>     total energy              =    -261.46803348 Ry
>>
>> for my case, is recommendable reduce the precision by default of the
>> energy
>> convergence from 1D-4 to 1D-3? i mean with 3 decimal is good for me, but i
>> don't know if a similar scheme happen at different electric field.
>>
>> Best Regards
>> Joaquín Peralta
>>
>> On Tue, Aug 31, 2010 at 1:59 AM, Tone Kokalj <tone.kokalj at ijs.si> wrote:
>>
>>  On Mon, 2010-08-30 at 14:43 -0500, joaquin peralta wrote:
>>> >
>>> > Sorry, I have now a slab put in the middle of the cell in the Z axis,
>>> > from z=32 to z=50 (maximum).
>>>
>>> I see. If the slab is located in the middle of the cell (i.e. at 0.5 in
>>> crystal units) then the dipole layer at 0.0 is OK!
>>>
>>> In this case here is the suggestion:
>>> Your 1 V/Angs is rather strong field. First perform SCF with lower field
>>> or no field (what Paolo suggested) and then use that as an input guess.
>>>
>>> Regards, Tone
>>>
>>> --
>>> Anton Kokalj
>>> J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
>>> (tel: +386-1-477-3523 // fax:+386-1-477-3822)
>>>
>>> Please, if possible, avoid sending me Word or PowerPoint attachments.
>>> See:  http://www.gnu.org/philosophy/no-word-attachments.html
>>>
>>>
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>>>
>>
>>
>> --
>> ----------------------------------------------------
>> Group of NanoMaterials
>> ----------------------------------------------------
>> http://www.gnm.cl
>> ----------------------------------------------------
>> Joaquín Andrés Peralta Camposano
>> ----------------------------------------------------
>> http://www.lpmd.cl/jperalta
>>
>> In a world without frontiers,
>> who needs Gates and Win.
>>
>>
>
>
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-- 
----------------------------------------------------
Group of NanoMaterials
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http://www.gnm.cl
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Joaquín Andrés Peralta Camposano
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http://www.lpmd.cl/jperalta

In a world without frontiers,
who needs Gates and Win.
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