[Wien] A question regarding a calculation for a 56 atoms unit cell

Mon Jun 6 10:47:18 CEST 2011

Dear Dr. Peter Blaha Sir,

We are using a version with MSEC1 in case.inm

Sir it was experimentally verified that it is an insulator (conductivity in
the range of 10^ -7 in room temperature).

Each iteration is taking 1hr. 50 mins and it has crossed already more than
60 iterations (considering time loss of around 10 hr due to power
failure....*but each time we have started from where it ends...we have used
"run anyway" option)*
*
*
Sir we have set OMP_NUM_THREAD = 8 and it using all the 8 processors as can
also been seen from CPU_MONITOR

Sir we will wait for another week and see what happens. We have data for
experimental band gap and we can compare it with the theoretically obtained
one.

Sir thank you very much for your reply.

with best regards,
Shamik Chakrabarti

On Mon, Jun 6, 2011 at 11:47 AM, Peter Blaha
<pblaha at theochem.tuwien.ac.at>wrote:

> Are you using a recent version with MSEC1 in case.inm or an older one ?
>
> As was mentioned several times gefore: changing the mixing parameter will
> most likely
> NOT help with the new methods.
>
> Using TEMP instead of TETRA may help convergence (but a too large value is
> dangerous).
>
> Do you have a metallic or insulating state (I understand it SHOULD be an
> insulator, but do
> you get it ?)
>
> How many iterations did you run ? Sometimes (but not very often) more than
> 40 are required ..
>
> Timing is strange. 56 atoms is not that big and it should not take a week
> ...
> (? 2-fold k-point parallelization ?; OMP_NUM_THREAD =2??? to utilize all 4
> cores ??)
>
> I guess nobody can answer if your convergence is sufficient or not. It
> depends on the prupose
> of your calculation. You need to monitor other
> quantities like MMT or MMIxxx, FER, forces, :GAP,....
>
> Am 05.06.2011 22:17, schrieb shamik chakrabarti:
>
>> Dear wien2k users,
>>
>>                        We are running a SCF calculation for a *56
>> inequivalent atoms* unit cell. We have included spin polarization and self
>> interaction correction (GGA+U) in
>> this calculation. The calculation has been run for one week now without
>> any errors. We are using a system having *Intel Xeon quad core processor and
>> 8GB RAM*. We are using *14 K
>> points* and a *mixing factor 0.1*. The energy and charge convergence were
>> achieved up to *0.04*. Once energy convergence has also gone up to 0.008 but
>> then again a bit diverges to
>> come up to 0.04. Now my question is::
>>
>> (1)  Is it possible to achieve charge and energy convergence up to 0.0001
>> with this unit cell using the above mentioned system if we consider that all
>> the interactions applied for
>> this
>>      material is proper?
>> (2) If it is achievable then can we estimate how much time it can take
>> given the no. of inequivalent atoms, K points, mixing parameter and nature
>> of the processor?
>> (3) If we are not able to achieve that much of convergence (0.0001) even
>> after a long time (say 2 weeks) then is it right to stop the calculation if
>> we achieve a stability in
>> convergence
>>     and say it is up to 0.01?
>> (4) If we take the convergence up to 0.01 then how much reliable will be
>> the further calculation of its properties (DOS) given the no. of K points is
>> 14?
>>
>> (5) If we do not get the convergence say at least up to 0.01 is it right
>> to increase the mixing parameter to say 0.15 or 0.20 given the system is a
>> *localized magnetic system*?
>>
>> The system is an insulator and also contain Fe. Thats why we have also
>> consider self interaction correction (GGA+U).
>>
>> Please forgive us for such a long email. We have to right it in this way
>> as the calculation has already been taken a long time and are indicating to
>> take longer time still.
>> Any reply in this regard will be very helpful for us. Thanks in advance.
>>
>> with best regards,
>>
>> --
>> Shamik Chakrabarti
>> Research Scholar
>> Dept. of Physics & Meteorology
>> Material Processing & Solid State Ionics Lab
>> IIT Kharagpur
>> Kharagpur 721302
>> INDIA
>>
>>
>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
>
> --
>
>                                      P.Blaha
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
> Email: blaha at theochem.tuwien.ac.at    WWW:
> http://info.tuwien.ac.at/theochem/
> --------------------------------------------------------------------------
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>

-- 
Shamik Chakrabarti
Research Scholar
Dept. of Physics & Meteorology
Material Processing & Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
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