[CP2K-user] [CP2K:15441] Re: Argon lattice constant

[sumit agrawal]

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 <sumitag... at gmail.com>
wrote:

> Thanks, Lucas....It's very helpful!!
>
> On Fri, May 21, 2021 at 10:32 PM Lucas Lodeiro <eluni... 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 (<sumitag... 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 <
>>> sumitag... 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 <nwi... 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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