[CP2K-user] [CP2K:15385] Unreasonable CELL_OPT result obtained for TiO2

[Hasan Al-Mahayni]

Hi,

I’m gonna jump in if you don’t mind. I am trying to do cell optimization
of  fcc copper. I used k points and got 3.65A  which is different from the
3.62 that was expected. I was wondering for your latter option (using a
large simulation cell) , would Run CELL_OPT or GEO_OPT?

On Sun, May 16, 2021 at 8:46 PM Krack Matthias (PSI) <matthi... at psi.ch>
wrote:

> Hi Yike
>
>
>
> Your simulation cell is small and you use no k point sampling. Either you
> use k point sampling or you enlarge your simulation cell to at least a cell
> edge length of 12 A in each direction. I suggest the latter option for
> CP2K. Furthermore, you could reduce EPS_DEFAULT to 1.0E-12 and increase
> REL_CUTOFF to 60.
>
>
>
> HTH
>
>
>
> Matthias
>
>
>
> *Von:* cp... at googlegroups.com <cp... at googlegroups.com> *Im Auftrag von *Yike
> Huang
> *Gesendet:* Sonntag, 16. Mai 2021 18:23
> *An:* cp2k <cp... at googlegroups.com>
> *Betreff:* [CP2K:15385] Unreasonable CELL_OPT result obtained for TiO2
>
>
>
> Hello, cp2k developers and users,
>
>
>
> I try to optimize primitive cell of rutile TiO2 by running CELL_OPT
> calculation at PBE+U(presently set to 0 eV)/DZVP level, but I find cell
> parameters deviate from experimental values quite quickly during
> calculation.
>
> I have tried changing STRESS_TENSOR to both NUMERICAL and ANALYTICAL but
> it does not help, I also think it may be not the reason why I get this kind
> of strange result.
>
> I attach my input script and CIF file below, are there any parameters in
> input script I forget?
>
> In addition, anatase TiO2 CELL_OPT task also has such problem, but I
> remember that primitive cell of Co3O4 can be successfully optimized.
>
>
>
> Thanks in advance.
>
>
>
> Yike Huang
>
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