[CP2K-user] [CP2K:12793] how to improve energy convergence parameters for water molecule in gapw

[hut... at chem.uzh.ch]

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.    
  -- 
 You received this message because you are subscribed to the Google Groups "cp2k" group.
 To unsubscribe from this group and stop receiving emails from it, send an email to cp... at googlegroups.com.
 To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/CAJ1pDDoM_DOHG6W4TS3a%3DXoVk3TEdARaijCQuCLSdsvKX67K5Q%40mail.gmail.com.
 

[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]