[CP2K-user] [CP2K:12146] Re: Problems in geometry optimization

Chn chen... at gmail.com
Thu Aug 29 13:31:07 UTC 2019


Dear Patrick,
Thanks a lot for your patient response! All these advices is really of 
great help to me, and the problem seems to be solved by setting &KPOINTS in 
&DFT section.
regards,
chn

在 2019年8月28日星期三 UTC+8下午8:30:20,Patrick Gono写道:
>
> Dear Chen,
>
> A CELL_OPT calculation automatically finds the optimal atomic 
> configuration as well. In general, the DFT lattice parameter will not be 
> identical to the experimental one. Therefore, it makes sense to run a 
> CELL_OPT calculation to determine the correct unit cell parameters and the 
> atomic structure. In practice, such calculations do not take much more time 
> than a GEO_OPT simulation. Note that in the case of bulk Pt, you know that 
> the cell is cubic, and thus can constrain the angles during CELL_OPT by 
> switching the option KEEP_ANGLES in the &CELL_OPT subsection of the &MOTION 
> section to true.
>
> But regarding your original issue: CP2K, by default, only uses a single 
> k-point, the Gamma point. Whereas in a plane-wave code you would converge 
> any results with respect to the k-point mesh density, in CP2K you must 
> converge the results with respect to the supercell size. I would suggest 
> running a CELL_OPT calculation with at least a 2x2x2, preferably a 3x3x3 
> supercell, and compare the lattice parameters with literature (still, the 
> number will be off due to the functional used, so compare with PBE results).
>
> Note that you must specify the MULTIPLE_UNIT_CELL keyword in both the 
> &TOPOLOGY and the &CELL subsections!
>
> Of course, get rid of that extra charge, you most probably want to study a 
> neutral system. And if you are dealing with bulk systems, keeping fixed the 
> position of an atom is not necessary, as the system will not float around. 
> This might only be relevant in the case of e.g. molecules or 2D sheets in 
> vacuum.
>
> Yours sincerely,
> Patrick Gono
>
> On Wed, 28 Aug 2019 at 12:54, Chn <ch... at gmail.com <javascript:>> wrote:
>
>> Dear Daniele,
>>
>> Thanks for your answer! I annotated the keyword "CHARGE" and the 
>> constraint part as you mentioned, but it still doesn't work. Could you 
>> please tell me some reasons that why does this situation happen in general? 
>> I am wandering that whether it is caused by the input file.
>> Does the variation of cell volume you mentioned above mean that I need to 
>> do the CELL_OPT before GEO_OPT?
>>
>> thanks again,
>> chn
>>
>> 在 2019年8月28日星期三 UTC+8下午5:26:58,Daniele Passerone写道:
>>>
>>> Dear Chn
>>>
>>> Apart from the size of the cell that could give you some trouble, the 
>>> problem is the keyword
>>>
>>> CHARGE 1
>>>
>>> that you added in the &DFT section, meaning that you are simulating a 
>>> charged system. Removing that would work.
>>>
>>> Indeed in the output we see:
>>>
>>>                           Hirshfeld Charges
>>>
>>>
>>>   #Atom  Element  Kind  Ref Charge     Population                    Net 
>>> charge
>>>
>>>       1       Pt     1      18.000         17.750                       
>>>   0.250
>>>
>>>       2       Pt     1      18.000         17.750                       
>>>   0.250
>>>
>>>       3       Pt     1      18.000         17.750                       
>>>   0.250
>>>
>>>       4       Pt     1      18.000         17.750                       
>>>   0.250
>>>
>>>
>>>   Total Charge                                                          
>>>   1.000
>>>
>>>
>>>
>>>
>>>
>>>
>>> Also not necessary is the constraint on the position of one atom that 
>>> you have in the optimization section.
>>> In general you should also vary the cell volume and find what is the 
>>> equilibrium volume for the PBE functional.
>>> Hope this helps
>>>
>>> Daniele
>>>
>>>
>>> On Wednesday, August 28, 2019 at 10:43:05 AM UTC+2, Chn wrote:
>>>>
>>>> Dear experts in CP2K,
>>>>
>>>> I am a learner of CP2K package and I am really thankful if my naive 
>>>> question can be explained.
>>>> I tried to do geometry optimization toward Pt bulk or Pt(111) by set 
>>>> the keyword "RUN_TYPE" as GEO_OPT and the *.inp file was referred to the 
>>>> exercises "Adsorption of acetylene on an intermetallic surface" about PdGa 
>>>> at CP2K website. But when the calculation done after several hours, I found 
>>>> that the atoms in cell distorted seriously. I think it should be obvious 
>>>> incorrect but I have no idea about how to fix it. Many thanks in advance.
>>>> The imported .xyz was prepared by using materials studio and VESTA. I 
>>>> have tried to use larger supercell (3*3*3) or to set the keyword 
>>>> "MULTIPLE_UNIT_CELL" as 3 3 3 and tried to optimize other structures like 
>>>> TiO2 but no use..is it that the cell I used still too small?
>>>> The attachments were the input files I used.
>>>>
>>>> Regards,
>>>> chn
>>>>
>>>> [image: o.png][image: d.png]
>>>>
>>>> -- 
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>
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