[Pw_forum] The total forces of TiO2(101) surface do not converge

[Giovanni Cantele]

It seems to me that the input positions are wrong. For example O25 and Ti27 positions are:
 O     0.50000    0.85806    0.30060
Ti    0.50001    0.67902    0.33161

Their distance is about 1 A, whereas Ti-O bond length is, as far as I remember, typically twice.

It is a good habit to visualise a structure (using for example XCrysDen) before attempting any calculation,
because in typical cases where two or more atoms are too close to each other or even overlap the sci
cycles would never (or quite hardly) converge.

Moreover, What I would do is try first the simplest run (e.g. calculation=‘sci’), removing all flags that could/should be set
only if you thing you need them (mixing_mode, diagonalization, mixing_ndim).

conv_thr seems too high.

Do you have norm conserving pseudo potentials? In the case remove ecutrho.

The k-point sampling along x and y directions is most probably insufficient for obtaining converged results, I would start
with a 4x4x1 k-point grid at least.

Giovanni

> On 7 Sep 2017, at 18:58, Andrey Chibisov <andreichibisov at yandex.ru> wrote:
> 
> Dear Colleagues.
> I am studing the TiO2(101) surface. But during the structure relaxation the total energy do not converge.
> I attach the input file.
>  
> -- 
> Best regards,
> Andrey Chibisov. Ph.D.
> Numerical method of mathematical physics Laboratory,
> Computational Center, Russian Academy of Sciences.
> Khabarovsk, Russia
> Web page: https://www.researchgate.net/profile/A_Chibisov
> http://ru.linkedin.com/pub/andrey-chibisov/55/253/986/en
>  
> <TiO2.in>_______________________________________________
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-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.fisica.unina.it/~cantele

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