[Smeagol-discuss] Convergence problem

[Zeila Zanolli]

Hi Ivan,

I'm always asking smeagol to converge the DM down to 1e-6 and - in  
most of the cases -  the convergence is achieved.
Saying that 1e-6 is too small for smeagol do you mean that
- in smeagol there are weaker tolerances and, hence, it doesn't make  
sense to ask for 1e-6?
- or that it is too difficoult, while still makes sense numerically,  
to achieve it?

When I had convergence problems, I had oscillations of the dDmax  
among something like 0.00n and 0.000n
and, honestly, this behaviour does not look nice to me....
i.e. can we trust such a calculation?


All the best,
Zeila



On 5 Feb 2010, at 11:39, Ivan Rungger wrote:

> Hello Nicolas,
>
>   can you please also send the CHR and buffer.out file for the input
> file you sent?
>
> You use a value of 1e-6 as tolerance for convergence DM.Tolerance, but
> this is too small for smeagol. Usually we converge the code to  
> 1e-4. I'd
> say for most cases once you get below 1e-3 the results are already  
> more
> or less OK, and once you get to 1e-4 they are for sure converged. I
> think if you use very well converged leads then it should be  
> possible to
> converge to 1e-5, but I think you will never get to 1e-6.
>
> Cheers,
>
>  Ivan
>
> Nicolas Leconte wrote:
>> Hi all,
>>
>> This question has been raised several times on the mailing list. I
>> tried several of the suggestions given, but none seemed to work  
>> for me.
>> I attach my input file.
>>
>> My system gets close to convergence on the *CHR file (should give a
>> value of about 1401 |e|) and the buffer.out file, but it oscillates
>> close to it without ever converging.
>>
>> I tried changing my basis (DZ instead of DZP), linear mixing and
>> NumberPulay 3, 5 and 10, NSlices 0 and 1, MD.Tolerance 0.00001 and
>> 0.000001. Maybe it is related to the small smearing with the flag
>> ElectronicTemperature, but I kinda need for my spin polarized
>> calculation. The EnergLowestBound is about 3 Ry lower than my lowest
>> EigenValue of my bulk calculation for the leads, so that shouldn't be
>> the cause either. I played with the integration points (on the circle
>> 8 --> 60, on the line 8 --> 60) and the number of poles : 5 --> 20.
>>
>> The Smeagol version used : smeagol-1.2
>>
>> Any advice?
>>
>> Thanks in advance,
>> Nicolas
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------------------------------------------------------------------------ 
---------------------
Dr. Zeila Zanolli

Université Catholique de Louvain (UCL)
Unité Physico-Chimie et de Physique des Matériaux (PCPM)
Place Croix du Sud, 1 (Boltzmann)
B-1348 Louvain-la-Neuve, Belgium
Phone: +32 (0)10 47 3501
Mobile: +32 (0)487 556699
Fax: +32 (0)10 47 3452
e-mail: zeila.zanolli at uclouvain.be
web: http://www.nano2hybrids.net/
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