[Pw_forum] "scf" calculation with "PBE0" hybrid functional

Narendranath Ghosh ghosh.naren13 at gmail.com
Mon Aug 8 22:39:57 CEST 2016 

Dear Dario
                I could not complete my last PBE0 "scf" job containing 434
atoms (CNT+Fullerene). The job could not stop but still running without
writing any more in the output file. These lines are written in  the output
34 hours ago .I have tried it twice but I found same thing.

     EXX: now go back to refine exchange calculation

     total cpu time spent up to now is    42069.2 secs

     Self-consistent Calculation

     iteration #  1     ecut=    30.00 Ry     beta=0.45
     Davidson diagonalization with overlap

I could not understand what's happening.I have used 24 node with 384
processors.I have alter ecut, cell length, beta values nothing happened.

Please suggest any idea.......



On Sun, Aug 7, 2016 at 10:53 AM, dario rocca <roccad at gmail.com> wrote:

> I will let the MD experts to reply to this question :)
>
> On Sat, Aug 6, 2016 at 2:49 AM, Narendranath Ghosh <
> ghosh.naren13 at gmail.com> wrote:
>
>> Dear Dario
>>
>> Thank you very much for your valuable suggestion. As my systems are quite
>> large and require high computational resources , I decided to compare one
>> of my result with that of PBE0.
>>
>> One problem that I am facing now "after successfully optimized the
>> (CNT+Fullerene) systems now I am looking for  to get 5 picosecond "md"
>> trajectory".
>> In QE which flags  allowed one to get *MD trajectories * *with NVE
>> ensemble. *I find some idea from http://qe-forge.org/piper
>> mail/pw_forum/2009-June/087573.html. But that is not clear to me.
>>
>> Please suggest any idea.....
>>
>> Thank you again
>>
>> *Narendra Nath Ghosh*
>>
>> *Research Associate*
>>
>> *University of Gour Banga*
>>
>> *Department of Computational Physics *
>>
>> *Malda-732102*
>>
>> *India*
>>
>> On Sat, Aug 6, 2016 at 10:48 AM, dario rocca <roccad at gmail.com> wrote:
>>
>>> Dear Narendra,
>>> If you do a PBE calculation with norm-conserving, ultrasoft, and PAW
>>> pseudopotentials very likely you will get very similar results (but it
>>> depends
>>> also on the quality of the pseudopotential, the property under
>>> consideration, etc.).
>>> In the case of PBE0 the type of pseudopotential will have a stronger
>>> effect on the final result.
>>> For purely esthetic reasons, if your previous calculations didn't take
>>> too long you could redo them with norm-conserving pseudopotentials and
>>> confirm that the results are indeed the same.
>>> Otherwise I don't see anything wrong in comparing, for example, a gap
>>> obtained at PBE level with US pseudos and a gap obtained at PBE0
>>> level with NC pseudos.
>>> Best,
>>> Dario
>>>
>>>
>>>
>>> On Fri, Aug 5, 2016 at 3:44 PM, Narendranath Ghosh <
>>> ghosh.naren13 at gmail.com> wrote:
>>>
>>>> Dear Dario
>>>>
>>>> Thank you very much  for your support.It works well and some of the
>>>> jobs have been finished successfully.
>>>>
>>>> But one thing in my mind. In my whole calculations , I used PBE with
>>>> ultrasoft pseudopotentials. But to do "scf" calculations with  PBE0 "hybrid"
>>>> functional I have to use "Norm conserving pseudopotential". So how can
>>>> I compare these two results.
>>>>
>>>> Please suggest any idea.....
>>>>
>>>> Thank you again
>>>>
>>>> *Narendra Nath Ghosh*
>>>>
>>>> *Research Associate*
>>>>
>>>> *University of Gour Banga*
>>>>
>>>> *Department of Computational Physics *
>>>>
>>>> *Malda-732102*
>>>>
>>>> *India*
>>>>
>>>>
>>>> On Thu, Aug 4, 2016 at 2:17 AM, dario rocca <roccad at gmail.com> wrote:
>>>>
>>>>> Dear Narendranath,
>>>>> Your calculation has reached convergence if you read the message "EXX
>>>>> self-consistency reached".
>>>>> You can learn some details about the scf procedure with hybrid
>>>>> functionals in PW/examples/EXX_example.
>>>>> PBE0 and hybrid functional calculations are in general very expensive.
>>>>> I would suggest you run an example to see what to expect.
>>>>> You might also try to perform a calculation on your system with
>>>>> minimal computational parameters (very small cut-off, few/one k-points)
>>>>> just to see that your run can indeed terminate smoothly. Then I would look
>>>>> for a set of parameters which are a good compromise between computational
>>>>> time and the accuracy you need.
>>>>> You might also try to modify the parameter ecutfock to gain some speed.
>>>>> For sure a hybrid functional calculation on a CNT+Fullerene system
>>>>> might be rather challenging.
>>>>> Best,
>>>>> Dario
>>>>>
>>>>> On Wed, Aug 3, 2016 at 11:16 AM, Narendranath Ghosh <
>>>>> ghosh.naren13 at gmail.com> wrote:
>>>>>
>>>>>> Dear all
>>>>>>
>>>>>>                    After optimizing a system "CNT+Fullerene" with
>>>>>> "PBE" I am trying to calculate "scf" calculation with "PBE0" hybrid
>>>>>> functional using  NC Pseudopotential.
>>>>>>
>>>>>> In output file I found "*convergence has been achieved in  15
>>>>>> iterations" *But the job was not finished even after more than one
>>>>>> week. I could not find any mistake in my input.
>>>>>>
>>>>>>
>>>>>> Please suggest any idea.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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