how to improve energy convergence parameters for water molecule in gapw

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pavan kumar behara

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Jan 20, 2020, 12:21:15 PM1/20/20
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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.
gamess-water.out
gamess-water.inp
water.basis
water.potential
cp2k-input.inp
cp2k-output.out

hut...@chem.uzh.ch

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Jan 22, 2020, 5:34:51 AM1/22/20
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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...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

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From: "pavan kumar behara"
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Date: 01/20/2020 06:21PM
Subject: [CP2K:12793] how to improve energy convergence parameters for water molecule in gapw
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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]

pavan kumar behara

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Jan 22, 2020, 9:05:31 AM1/22/20
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Thank you very much Prof. Hutter.



--
==================================
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
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