[Pw_forum] CuBTC open metal organic frameworks CONVERGENCE

[Francesco Pelizza]

Thank you very much Nicola, I am going to set the runs immediately and I 
will let you know if the problem persist.


Grazie mille !!



On 23/01/17 11:53, Nicola Marzari wrote:
> On 23/01/2017 12:37, Francesco Pelizza wrote:
>> Hello dear community,
>>
>>
>> Here in strathclyde some colleagues are using QE to relax and than study
>> some MOF's.
>>
>> The problem starts from the beginning, no convergence in the first SCF
>> cycle before a fixed cell relaxation.
>
> One more, if unrelated - the conv_thr you use is extremely tight
> (this is not related to your original problem, but it only means that
> once you have found a robus recipe for convergence, it might be tough
> to get to such a tight tolerance). This is because, as mentioned in
>
> http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html
> ---
> Convergence threshold for selfconsistency:
>      estimated energy error < conv_thr
> (note that conv_thr is extensive, like the total energy).
> ---
>
> it means that if say 1e-6 is a good conv_thr value for a system with a
> few atoms,
> if a system is 10 times larger conv_thr should typically be 10 times larger
> as well (i.e. 1e-5)
>
> 			nicola
>
>
>
>>
>> We took care of spin polarized calculation, switched to non polarized
>> calculation and many other things, WFC from 50 to 80 Ry and RHO cutoffs
>> 10 times the WFC, with gamma sampling and 3 x 3 x 3.
>>
>> Also checked the smearing, degauss values, nothing seemed to make the
>> convergence better.
>>
>> Here you can find some input files and output files.
>>
>>
>> We used ultrasoft pseudopotentials applying PBE and then vdW-DF
>> functionals.
>>
>>
>> No success at all.
>>
>>
>> Please some of you have better experience of us in these systems to tell
>> us what we do wrong?
>>
>>
>> BW
>>
>> Francesco Pelizza and Chris Campbell
>>
>>
>> Strathclyde University
>>
>>
>>
>>
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