[CP2K-user] [CP2K:12801] how to improve energy convergence parameters for water molecule in gapw

[pavan kumar behara]

Thank you very much Prof. Hutter.

On Wed, Jan 22, 2020 at 5:34 AM <hut... at chem.uzh.ch> wrote:

> Hi
>
> the GAPW accuracy (compared to QC codes) depends also on your
> basis set. Small basis sets (like 6-31G*) have typically a
> larger error than large basis sets (see also the literature for examples).
>
> Besides that, there are many possible parameters besides the Lebedev grids
> that
> could be adjusted. I don't think they will make a difference, but you
> never know
>
> CP2K_INPUT / FORCE_EVAL / DFT / QS
>
> EPSFIT
> EPSISO
> EPSRHO0
> LADDN0
> LMAXN0
> LMAXN1
> ALPHA0_HARD
>
> best 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
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----cp... at googlegroups.com wrote: -----
> To: cp... at googlegroups.com
> From: "pavan kumar behara"
> Sent by: cp... at googlegroups.com
> Date: 01/20/2020 06:21PM
> Subject: [CP2K:12793] how to improve energy convergence parameters for
> water molecule in gapw
>
>
> Hello CP2K developers,
>
> I am using CP2K-6.1  and performed HF energy calculation for water
> molecule using GAPW method with an all electron basis. I used UHF for the
> run. When I use the same basis set and do the  same calculation with Gamess
> package (using spherical harmonics), I  observed energy differences of the
> order of 1E-04 with CP2K. I encountered similar issue before for atoms and
> increasing the size of atomic grids (lebedev and radial) and tightening
> convergence parameters solved it. Even with tighter convergence I am
> getting a slight mismatch for water molecule calculation. It was mentioned
> in an earlier post that it is common to observe energy differences in few
> microhartree for small molecules with GAPW method. Is it okay to ignore
> this small difference or is there a chance to improve my calculation?
>
>     Energy in a.u.        CP2K    -76.01997566        GAMESS
> -76.02037291        difference    0.000397257
>
> I attached all the inputs and outputs for cp2k as well as gamess for your
> reference.
>
> Thank you very much for your time, any help is appreciated.
>
>
> Best regards,
> Pavan.
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> .
>
>
> [attachment "cp2k-input.inp" removed by Jürg Hutter/at/UZH]
> [attachment "gamess-water.out" removed by Jürg Hutter/at/UZH]
> [attachment "gamess-water.inp" removed by Jürg Hutter/at/UZH]
> [attachment "cp2k-output.out" removed by Jürg Hutter/at/UZH]
> [attachment "water.basis" removed by Jürg Hutter/at/UZH]
> [attachment "water.potential" removed by Jürg Hutter/at/UZH]
>
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> .
>


-- 
==================================
Pavan Kumar Behara
Department of Chemical and Biological Engineering
514 Furnas Hall
University at Buffalo, The State University of New York
Buffalo, NY 14260-4200
Tel: 814-441-7156
<ko... at buffalo.edu>
www.linkedin.com/pub/pavan-kumar-behara/1a/23b/a02/
==================================
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