[CP2K-user] [CP2K:15441] Re: Argon lattice constant
Travis
polla... at gmail.com
Sat May 22 21:04:00 UTC 2021
Hi,
Symmetry...
fcc crystal: 8 corners shared across 8 cells + 6 faces shared across 2
cells, reduced is 8*(1/8) + 6*(0.5) = 1 + 3 = 4 atoms. The CIF file has 4
atoms.
-T
On Saturday, May 22, 2021 at 9:11:56 AM UTC-4 sum... at gmail.com wrote:
> I have one more query: When we construct a fcc lattice there will be 14
> atoms (8 at the corner of the cube and 6 at center of the faces) in a 1x1x1
> unit cell. But when we download an argon crystal structure file from a
> material project, there are only four atoms. Why is this so?
>
> Here is the download file.
>
> On Sat, May 22, 2021 at 6:31 PM sumit agrawal <sum... at gmail.com>
> wrote:
>
>> Thanks, Lucas....It's very helpful!!
>>
>> On Fri, May 21, 2021 at 10:32 PM Lucas Lodeiro <el... at gmail.com>
>> wrote:
>>
>>> at the end of MP page, there is a table, # of K-points, when no kpoints
>>> are used, the calculation is computed on gamma point.
>>> About the functional... it is important to search some literature about
>>> your system and used functionals... but HSE06 is a good one for almost all
>>> solid state calculations.
>>>
>>> El mié, 19 may 2021 a las 5:17, sumit agrawal (<sum... at gmail.com>)
>>> escribió:
>>>
>>>> Thanks Lucas,
>>>>
>>>> Your suggestions are very helpful and informative.
>>>>
>>>> I have the following queries :
>>>>
>>>> Where it is mentioned that calculation is done using gamma points? In
>>>> the calculation summary I haven't found this.
>>>>
>>>> Second, can you suggest some good hybrid functional for such types of
>>>> calculations?
>>>>
>>>> Third, when I want to choose a lattice structure for my crystal (here
>>>> for argon it is fcc which is cubic in nature) from a material project,
>>>> which space group should I choose? I can see there are two space groups for
>>>> agon cubic structure (m3m and 6/mmm). For m-3m i can see all the
>>>> angles are 90 degree but for 6/mmm angles are not 90 degree then how could
>>>> it be a cubic structure ? Should I go with m-3m only then ?
>>>>
>>>> Thanks,
>>>> Sumit
>>>>
>>>> On Wed, May 19, 2021 at 12:48 PM sumit agrawal <sum... at gmail.com>
>>>> wrote:
>>>>
>>>>> Dear Nicholas,
>>>>>
>>>>> I also found it is 5.64 A on the Materials project. But i want to
>>>>> reproduce data from the following paper. In this paper they have calculated
>>>>> 5.2226 A.
>>>>>
>>>>> One query about kpoint mesh: I also use "SCHEME MONKHORST-PACK 8 8
>>>>> 8". Here also I get the cell constant of 5.54 A, but I am not getting below
>>>>> 5.54 A.
>>>>>
>>>>>
>>>>> PFA
>>>>>
>>>>>
>>>>> Phys. Chem. Chem. Phys., 2015, 17, 17159-17168
>>>>>
>>>>>
>>>>>
>>>>> On Wed, May 19, 2021 at 1:34 AM Nicholas Winner <n... at berkeley.edu>
>>>>> wrote:
>>>>>
>>>>>> Where is it reported as 5.2229A? On Materials Project, using PBE with
>>>>>> VASP, they calculated 5.64A as the lattice constant. Considering you are
>>>>>> using a dispersion correction, your calculation seems reasonably close to
>>>>>> that. If you're sure that 5.2229 is the 'correct' answer using PBE+D3 then
>>>>>> consider using a finer kpoint mesh.
>>>>>>
>>>>>> On Tuesday, May 18, 2021 at 12:04:31 AM UTC-7 sum... at gmail.com
>>>>>> wrote:
>>>>>>
>>>>>>> Dear cp2k users,
>>>>>>>
>>>>>>> I am trying to optimize the argon unit cell using KPOINTS. The
>>>>>>> reported cell constant for argon is 5.2229 A. But I am getting a cell
>>>>>>> constant of 5.5435 A. I have prepared a unit cell with the dimension of
>>>>>>> 5.2229 A. Then in the $CELL section I mention the same dimension.
>>>>>>>
>>>>>>> Here I am attaching my input and output files.
>>>>>>>
>>>>>>> Please give suggestions!!!
>>>>>>>
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>>>>>> .
>>>>>>
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>>
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