[QE-users] problem using vc-relax with organic crystal structure

[Paolo Giannozzi]

The input data use PBE + DFT-D3, that should do a decent job with
dispersion forces

Paolo

On Wed, Dec 2, 2020 at 10:13 PM Stefano Baroni <baroni at sissa.it> wrote:

> Besides, intermolecular distances in a molecular crystal sensitively
> depend on the XC functional, all of which have a hard time properly
> accounting for dispersion forces (some of them a worse time than others). SB
>
> On 2 Dec 2020, at 19:38, Claudio A. Perottoni <caperott at gmail.com> wrote:
>
> Dear Corrado,
>
> The ecutwfc in your input file seems a bit small. You may try using
> https://www.materialscloud.org/work/tools/qeinputgenerator to generate an
> input file for optimizing the crystal structure of your compound.
> Best regards,
> Claudio
>
>
> On Wed, Dec 2, 2020 at 3:15 PM Cuocci Corrado <corrado.cuocci at gmail.com>
> wrote:
>
>> I have determined the crystal structure of new organic compound from
>> X-ray powder diffraction data.
>>
>> First of all, I used quantum espresso to validate my new structure in a
>> 'relax' calculation obtaining a result in a good agreement with the
>> experimental structure.
>>
>> In a second step I tried to perform a 'vc-relax' but in this case the
>> result seems chemically unreasonable: I observed a large variation of
>> the cell parameters, final density too high for this type of compound,
>> short intermolecular distances.
>> Input and output files can be downloaded from:
>> https://cloud.ba.cnr.it/index.php/s/5RmA7MqA9gJeRdx/download
>> https://cloud.ba.cnr.it/index.php/s/qmnAwM5JeqDnHdG/download
>>
>> My experience in the use of the program is limited and I suspect I have
>> made some mistakes.
>> Do you have any suggestions to improve the calculation?
>>
>> Thanks a lot.
>> Corrado
>> --
>> ============================================
>> Cuocci Corrado
>> Istituto di Cristallografia - CNR
>> Via G. Amendola,122/o
>> 70126 Bari (Italy)
>> tel: +390805929161
>> fax:+390805929170
>> corrado.cuocci at ic.cnr.it
>> ============================================
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>> users mailing list users at lists.quantum-espresso.org
>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>
>
>
> --
>
> *Claudio A. Perottoni*
>
> Universidade de Caxias do Sul
> 95070-560 Caxias do Sul - RS - Brazil
> http://www.researcherid.com/rid/B-8409-2008
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users



-- 
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
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