[CP2K-user] [CP2K:15419] Re: Argon lattice constant

[Lucas Lodeiro]

If you have the reference for that lattice constant, share it... I do a
short search and I cannot find something similar. For example in
https://doi.org/10.1063/1.1726009 says that the lattice constant is 5.3A.
Nicholas comments about materials Project data, probably this:
https://materialsproject.org/materials/mp-23155/
About materials Project data, is worth mentioning, the calculation was done
using just the gamma point, which does not appear to be a converged
calculation. Also the MP lattice constant is larger than experimental data.

Probably if you use a higher kpoint grid, higher cutoff and a little bit
larger basis set, your calculation will get closer to experimental data,
but do not think GGA DFT functionals (PBE among others) will give you
exactly the correct lattice constant. Depending on what you want in terms
of precision, maybe a hybrid functional will be necessary to improve the
lattice constant, but remember that hybrid functional are more expensive
than GGA ones... you have to define a proper balance between precision and
cost.

regards

El mar, 18 may 2021 a las 17:04, Nicholas Winner (<nwi... at berkeley.edu>)
escribió:

> 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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