[CP2K-user] [CP2K:15650] geometry optimization completed

[Tahere Kheshti]

Dear Fabian

I am interested in studying the structural, electronic, and optical
properties of periodic systems. I used to calculate the gas phase using
Gaussian software. Now for the first time, I want to calculate in
solid-state by cp2k. I have got some basic questions about periodic
calculations. Please forgive me if I am asking very general questions, and
so many....!

I want to start from the crystal X-ray structure...you can see it in the
attached file!

1) Can I replace some of its atoms with arbitrary atoms? for example F atom
instead of H atom... If I can, I must do calculations by cell-opt run
type??? or geo-opt is also good?!

 2) As you see in the attached file, in my x-ray unit cell, there are some
atoms outside of the box.  Should such atoms be deleted before converting
the CIF file to XYZ format? or not?

3) Can this structure be investigated in 2D?

4) If I want to investigate the electronic and optical properties of this
structure, can I use the single unit cell or should it be in the form of a
supercell? Are the properties of the unit cell and supercell different?

5) There is an important physical concept in the solid-state called k
point! Is it necessary to enter its keyword ?! or it is set by default...I
don't know?  Do you think I should enter it in the input file? whether
unit-cell or supercell!


I am very sincerely eager to get an answer? please.

Thanks a lot for helping

On Tue, Jun 29, 2021 at 12:05 AM Tahere Kheshti <tahere... at gmail.com>
wrote:

> Dear Thomas
>
> Thanks for your helping! I am a new user and I do not know some points.
>
> Do you mean to use the default value for the number of optimization steps?
> Yes, unfortunately in the convergence of SCF, DIIS switched to SD, you
> suggested that I reduce the size. What value is good?
>
> On Mon, Jun 28, 2021 at 11:57 PM fa... at gmail.com <fabia... at gmail.com>
> wrote:
>
>> Hi
>>
>> Your initial guess seems to be pretty bad: The structure at step 0 has a
>> pressure of 5'546'592 bar and the first BFGS iteration reduces the energy
>> by more than 50 Hartree, which is enormous. The volume of your cell
>> increases by a factor of 2 over the 30 BFGS iterations. Maybe you could try
>> to improve the initial configuration. This would certainly help the
>> convergence of the SCF and BFGS.
>>
>> Cheers Fabian
>> On Monday, 28 June 2021 at 20:50:52 UTC+2 tkuehne wrote:
>>
>>> Dear Tahere,
>>>
>>> your geometry optimization is far from being converged. Instead of
>>> limiting the number
>>> of optimization steps to 30, better simply rely on the convergence
>>> criteria.
>>> SCF convergence, however, is much better when OT switches into the SD
>>> fallback mode
>>> is always bad news. Try to reduce the OT stepsize …
>>>
>>> Best,
>>> Thomas
>>>
>>> Am 28.06.2021 um 17:39 schrieb Tahere Kheshti <tah... at gmail.com>:
>>>
>>> Hello everyone
>>> I am attaching the input and output files. As you see none of the
>>> criteria for optimized geometry has been reached. Do I need to increase
>>> the number of optimization steps? how many is enough? (my structure has
>>> 114 atoms)
>>> Are the number of inner and outer SCF steps appropriate?
>>>
>>> Can you please tell me your suggestions?
>>> Thanks
>>>
>>>
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>>> .
>>> <In2Cl10C20H12Br4N4F8pbc.inp><In2Cl10C20H12Br4N4F8pbc.out>
>>>
>>>
>>> ==============================
>>> Thomas D. Kühne
>>> Dynamics of Condensed Matter
>>> Chair of Theoretical Chemistry
>>> University of Paderborn
>>> Warburger Str. 100
>>> D-33098 Paderborn
>>> Germany
>>> tho... at upb.de
>>> +49/(0)5251/60-5726 <+49%205251%20605726>
>>>
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