[Q-e-developers] problem in DFT+U: muted U_projection_type

[Andrea Ferretti]

I've done the commit to the main trunk, though I was rejected when 
attempting to commit on GIPAW (I attach a patch with the changes toi be 
applied).

concerning the tests, we can surely add one of those that were showing the 
problem (perhaps made a bit more general eg including kpts)

Andrea

> By the way: variable U_projection_type is never tested anywhere. With
> a test this wouldn't have happened (or wouldn't have gone unnoticed
> for so long)
>
> Paolo
>
> On Thu, May 25, 2017 at 10:55 AM, Paolo Giannozzi
> <paolo.giannozzi at uniud.it> wrote:
>> Oops ... I think I forgot that piece of code when I deleted "npw" as
>> global variable almost everywhere. The patch is perfect. If you commit
>> please also add a line in Doc/release-notes.
>>
>> Paolo
>>
>> On Thu, May 25, 2017 at 10:30 AM, Andrea Ferretti
>> <andrea.ferretti at nano.cnr.it> wrote:
>>>
>>> Dear All,
>>>
>>> while looking at some tests using DFT+U, Mike and I found an issue related
>>> to the input variable U_projection_type:
>>>
>>> in a situation where the overlap of U-atomic orbitals is quite large, we
>>> find no difference in the pw output when setting
>>>
>>> U_projection_type = "atomic"        # no orthonormalization
>>> U_projection_type = "ortho-atomic"  # orthogonalization and normaliz
>>> U_projection_type = "norm-atomic"   # no orthogonalization, just normaliz
>>>
>>> except for an output message saying that the variable was read consistenly.
>>>
>>> One can also see that the occupations on the Hubbard manifold sum to a
>>> number of electrons larger that the actual N, suggesting that the basis is
>>> either not orthogonal or not normalized or both.
>>>
>>> The problem is present since qe-6.0 (espresso 5.3.0 works fine with me)
>>>
>>> After a bit of investigation, we found that the problem is in
>>> PW/src/orthoatwfc.f90, where, in ortho_swfc
>>>
>>> npw is used from a module but apparently is not initialized (or init to 0)
>>> resulting in zero overlap matrix (collinear case) and basically leaving
>>> unchanged the atomic vectors which were to be orthogonalized/normalized.
>>> (it is also funny that pw.x, compiled with intel 12, didn't complain about a
>>> zero ovp while taking ovp^-1/2)
>>>
>>> ----
>>>
>>> the problem should be of little impact for reasonably localized (and
>>> normalized) d/f states, which do not change too much upon lowding ortho
>>> procedure, while more evident on p and s states (though luckily less
>>> relevant physically)
>>>
>>> ----
>>>
>>> In order to fix the problem we have slightly changed the interface of
>>> ortho_swfc passing npw explicitly (similarly yo what is done for init_us_2
>>> or calbec)
>>>
>>> attached the fixed version and a patch showing the changes.
>>>
>>> ortho_swfc is also used in a couple of other places (Xspectra and GIPAW),
>>> which need to be changed accordingly (not a big deal apparently)
>>>
>>> If there are no strong opinions against, I'll commit (the only other option
>>> I see is to pass the info via modules, which I don't like too much, getting
>>> the code flow more implicit and entangled)
>>>
>>> Take care
>>> Andrea
>>>
>>>
>>>
>>> --
>>> Andrea Ferretti, PhD
>>> S3 Center, Istituto Nanoscienze, CNR
>>> via Campi 213/A, 41125, Modena, Italy
>>> Tel: +39 059 2055322;  Skype: andrea_ferretti
>>> URL: http://www.nano.cnr.it
>>>
>>> _______________________________________________
>>> Q-e-developers mailing list
>>> Q-e-developers at qe-forge.org
>>> http://qe-forge.org/mailman/listinfo/q-e-developers
>>>
>>
>>
>>
>> --
>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>> Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>

-- 
Andrea Ferretti, PhD
S3 Center, Istituto Nanoscienze, CNR
via Campi 213/A, 41125, Modena, Italy
Tel: +39 059 2055322;  Skype: andrea_ferretti
URL: http://www.nano.cnr.it
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