[CP2K-user] [CP2K:15577] Poor force convergence wrt basis set size

[Arthur France-Lanord]

Hi,

Thank you for the suggestion. This contributed to reducing the noise on the
forces, and MAE's are now ~ 30% smaller. However, I still observe almost
similar performances for MOLOPT basis sets (from DZVP-MOLOPT-SR to
TZV2P-MOLOPT, vs. TZV2PX-MOLOPT). In fact, the MAE is even slightly smaller
for the smallest, short-range version of DZVP-MOLOPT. Could that be a
symptom of over-completeness of basis sets including diffuse functions for
this system?

best,
Arthur

Le mer. 16 juin 2021 à 10:56, <hut... at chem.uzh.ch> a écrit :

> Hi
>
> I to be sure that you don't pick up basis set dependent numerical noise
> I would suggest to use a more strict eps_default value, e.g. 1.E-14.
>
> regards
>
> Juerg Hutter
> --------------------------------------------------------------
> Juerg Hutter                         Phone : ++41 44 635 4491
> Institut für Chemie C                FAX   : ++41 44 635 6838
> Universität Zürich                   E-mail: hut... at chem.uzh.ch
> Winterthurerstrasse 190
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>
> -----cp... at googlegroups.com wrote: -----
> To: "cp2k" <cp... at googlegroups.com>
> From: "Arthur France-Lanord"
> Sent by: cp... at googlegroups.com
> Date: 06/06/2021 12:01PM
> Subject: [CP2K:15521] Poor force convergence wrt basis set size
>
> Hi,
>
> I'm currently testing atomic force convergence with respect to basis set
> size, for a crystalline polymorph of sulfur (an array of cyclic S8
> molecules). I've tested both standard GTH basis sets (DZVP to QZV2P
> compared to QZV3P), and MOLOPT (DZVP-MOLOPT-SR to TZV2P-MOLOPT compared to
> TZV2PX-MOLOPT). I'm observing a slow or poor convergence behavior, which
> can be seen in these two plots (MAE : mean absolute error, MAPE : mean
> absolute percentage error, both only computed on the x components of the
> forces):
>
> GTH basis sets:
>
>
> MOLOPT basis sets (the TZV2P-MOLOPT/QZV3P panel is just shown here for
> comparison) :
>
>
> In particular, TZVP-MOLOPT performs slightly better than TZV2P-MOLOPT..?
> I'm using a high energy cutoff (2500 Ry and a REL_CUTOFF of 100 Ry), and a
> rather tight SCF convergence criterion (1.0e-7) with the OT method.
> Convergence in the SCF is achieved rather fast.
>
> Are these errors expected? I was trying to reproduce something similar
> from what ccan be seen in https://arxiv.org/pdf/1409.4527.pdf (figures 1
> and 2), but didn't expect such high relative errors. The configuration I'm
> using is from a molecular dynamics run to obtain non-zero forces. I'm
> including a cp2k input file to reproduce the QZV3P calculation.
>
> many thanks,
> Arthur
>
>
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