[CP2K-user] [CP2K:19288] Band gap-HSE06-UiO-66

[Jingyun Ye]

Hello Lucas,

Thank you for sharing your thoughts. So normally for the MOFs system,
either VASP or CP2K, gama point is usually selected for calculation since
the unit cell has several hundreds of atoms. For the test materials, it
only has the direct band gap.

The xyz coordinate, lattice constants are the same for both VASP and CP2K
tests.

I don't think it is because of  EPS_DEFAULT, EPS_PGF_ORB because they are
in the magnitudes of -14, and -60.

I used the basis set: DZVP and auxiliary basis set (ADMM): a combination of
c-FIT11 and cFIT3, which are the maximum I can afford, or else, the
calculation will run out of memory. I think this might be the case for the
large systems.

Could you please share more about the CUTOFF? You mean the GHT basis set
(400) and plane wave cutoff (60), right? I think my cutoff is reasonable
since I test the convergence for energy but for PBE functional.

I think this will be a very helpful discussion for all.

Thank you,
Jenny





On Tue, Oct 3, 2023 at 6:48 PM Lucas Lodeiro <elunicolomo at gmail.com> wrote:

> Hello Jenny,
>
> AFAIK HSE functional is shortrange functional by definition... it is
> constructed using the erf(wr) technique and leaving only the short range
> term. WRT the value of the band gap, the band gap is very dependent on the
> reciprocal space sampling, whether the band gap is not vertical in
> reciprocal space or either the eigenvalues are highly dependent on the
> sampling, so I guess you use kpoints in VASP, did you use the same
> structure/cell and kpoints in CP2K instead? This is very important to
> compare both results.
> Also, the accuracy must be set by your calculation settings, as
> EPS_DEFAULT, EPS_PGF_ORB, your basis set and auxiliary basis set (ADMM).
> Also the possible screening for the HF part, and the cutoff, which must be
> sufficient long to ensure the short range decay to low values...
> Regards - Lucas
>
> El mar, 3 oct 2023 a las 17:37, jingyu... at gmail.com (<
> jingyun.ye324 at gmail.com>) escribió:
>
>> Hello everyone,
>>
>> I am trying to compare with HSE06 functional using VASP and CP2K. I found
>> out that the band gap calculated using VASP is about 3.7 eV for UiO-66
>> which is very close to the experimental value 3.6-3.7 eV.
>>
>> However, when I use CP2K, the band gap is 4.07 eV, which is almost the
>> same with the data reported by the following paper.  (Understanding
>> Intrinsic Light Absorption Properties of UiO-66 Frameworks: A Combined
>> Theoretical and Experimental Study, *Inorg. Chem.* 2015, 54, 22,
>> 10701–10710)
>>
>> I wonder if the developer could comment on the accuracy? Or any room to
>> improve the accuracy.  (HSE06 functional section I used is the default
>> that posted on the CP2K website or lectures by Dr. Sanliang Ling. )
>>
>> Another question: Only shortrange keyword is allowed to use for HSE06?
>>
>> Thank you,
>> Jenny
>>
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