[CP2K-user] [CP2K:18648] About cutoff benchmarking in Cerium(III) chloride

[Lucas Lodeiro]

Hello Aditya,

It is not clear what basis set you are using, since there are two
DZVP-MOLOPT-SR-GTH for Ce, one with 12 electrons (-q12) and another with 30
electrons (-q30).
In my experience the best approach to know a cutoff estimate is from the
HIGHER_COEFFICIENT in the whole basis set. Taking the result from
HIGHER_COEFFICIENT*REL_CUTOFF you can get an approximate CUTOFF for
convergence.
>From BASIS_MOLOPT_UCL file, the DZVP-MOLOPT-SR-GTH-q12 basis set has
a  HIGHER_COEFFICIENT of 4.348 and DZVP-MOLOPT-SR-GTH-q30  basis set has
a  HIGHER_COEFFICIENT of 18.922, so with a REL_CUTOFF of 60Ry, the
convergence must be reached at 260Ry and 1135Ry respectively.
Also, if you are using smoothers (XC_GRID section), the convergence test
behavior will not be as expected, with a monotonous convergence... in my
experience always show more oscillations...
A last thing, the EPS_DEFAULT and EPS_SCF values are important to reach a
good CUTOFF convergence, values of 1E-12 and 1E-06, respectively, are
usually good.

Regards - Lucas

El mar, 11 abr 2023 a las 3:33, Aditya Goyal (<goyal.aditya74 at gmail.com>)
escribió:

> Dear CP2K users,
> I'm trying to simulate a molten cerium chloride system with 40CeCl3
> molecules. Before performing any extensive calculation, I'm trying to
> benchmark the cutoff energy used in the DFT section by performing
> single-point energy calculations. I'm using DZVP basis sets for Ce & Cl
> with PBE functional by taking 800 Ry as a benchmark for comparison.
>
> For a Relative cutoff of 60 Ry
> Cutoff          Energy(Ha)               Delta E (kJ/mol) wrt. 800 Ry
> 350 Ry -3357.32389476218      3.61119311934135
> 550 Ry -3357.3063307436      49.7255239006927
> 600 Ry -3357.27607335904     129.166287063426
> 650 Ry -3357.28237568966     112.619518020088
> 700 Ry -3357.31280473755      32.7280527853891
> 750 Ry -3357.31982535559      14.2954201205428
> 800 Ry -3357.32527019281       0.00000000000000
>
> Similarly, For a Relative cutoff of 100 Ry
> Cutoff          Energy(Ha)               Delta E (kJ/mol) wrt. 800 Ry
> 350 Ry -3357.31559413633    -49.9141589061937
> 550 Ry -3357.3107413093    -37.1730615379035
> 600 Ry -3357.29750596273      -2.42365911922866
> 650 Ry -3357.33819509308    -109.252970852155
> 700 Ry -3357.32224091494     -67.3652761456795
> 750 Ry -3357.30040482541     -10.0346230856023
> 800 Ry -3357.29658283985      0.00000000000000
>
> So, I'm not finding a convergence of energy or any particular trend at any
> cutoff (for both relative cutoff cases). Can anyone suggest some parameter
> changes that may be used to achieve convergence? Any help would be
> appreciated.
>
> Regards
> Aditya
>
>
>
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