[gpaw-users] Convergence issue with mBEEF

[Jess Wellendorff]

Marcin: The mBEEf functional was fitted on PBEsol electron densities 
obtained using rather tight SCF criteria. I think something else must be 
the root cause of this issue. Perhaps GPAW does not supply LibXC with 
sufficiently accurate kinetic energy densities?

Monish: Honestly, I believe the only solution to your problem is to 
lower the SCF convergence criteria, perhaps even completely eliminate 
them for the eigenstates and rely only on density and energy criteria. I 
have successfully used this approach. It is not pretty, but it works :)

If you take a look at the mBEEF test script (gpaw/test/mbeef.py), the 
SCF criteria for very quick molecular calculatios are set to 
{'eigenstates':1.e+2, 'density':1.e-2, 'energy':1.e-4}. These are 
bullet-proof settings for a simple test. In general, the density and 
energy criteria can probably be tightened more. Also, I would expect the 
eigenstate issue to be much less pronounced in bulk calculations.

Hope this helps.
Best,
Jess

On 11/25/2014 06:53 PM, Marcin Dulak wrote:
> On 11/25/2014 04:37 PM, Wellendorff, Jess wrote:
>> Hi Monish, in my experience, the eigenstates can be hard to converge 
>> with metagga. Is this your problem?
> i remember even with the older BEEF-vdW molecules are hard to converge.
> Maybe this is due to loose SCF thresholds used when fitting the 
> functional (was it the case also for mBEEF?),
> so the resulting functional by design is not reaching a tight 
> convergence.
>
> Best regards,
>
> Marcin
>>
>> Best,
>> Jess
>>
>>
>>> On Nov 25, 2014, at 14:48, mohnish pandey <mohnish.iitk at gmail.com> 
>>> wrote:
>>>
>>> Dear all,
>>>
>>> I am trying to do some test calculations with mBEEF functional for 
>>> some solids like ZnO. But I am facing difficulty in converging the 
>>> calculations. I tried tweaking mixing, Fermi temperature etc, but it 
>>> didn't help. Would really appreciate if somebody helps me out with 
>>> the issue. Thanks a lot in advance.
>>>
>>> -- 
>>> Regards,
>>> Mohnish,
>>> -----------------------------------------------------------------
>>> Mohnish Pandey,
>>> PhD Student,
>>> Center for Atomic-scale Materials Design,
>>> Department of Physics,
>>> Technical University of Denmark
>>> -----------------------------------------------------------------
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>>> gpaw-users mailing list
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