[CP2K:3477] energy convergence question

hut... at pci.uzh.ch hut... at pci.uzh.ch
Fri Sep 2 17:15:18 UTC 2011


if you change the box size for a given cutoff you might get
oscillations due to the integer number of grid points.

- Test the cutoff for a fixed box size by increasing the cutoff
  (I would use larger intervals and higher cutoffs if convergence
    is important)

- find the best box size at this cutoff by enlarging the box.
  Use isolated boundary conditions (Ewald method and periodicity none)
  for best results.



Juerg Hutter                         Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich               E-mail:  hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland

-----cp... at googlegroups.com wrote: -----
To: cp... at googlegroups.com, s.me... at caspur.it
From: Alin Marin Elena 
Sent by: cp... at googlegroups.com
Date: 08/31/2011 01:06PM
Subject: [CP2K:3477] energy convergence question

Dear All,

I try to determine the good box size and density cut-off for a small cluster 
(HF(H_2O)_7) for HCTH120 functional.
However the results that I obtained left me with few questions.
I played with three functionals PBE, BLYP and HCTH120 for different cut-offs 
(280 to 330 in step of 10Ry and Ngrid 5) and plotted the total energy for each 
of them against the box size (a cube) -- see the attached figures pbe.eps, 
blyp.eps and hcth.eps. The calculation seems to converge after but I am a 
little bit troubled by the oscillation that shows. 

Do I miss anything in my input that gives this behaviour?
I attached the input files too..

I used the TZV2P basis set from this
# Joost VandeVondele and Juerg Hutter
# J. Chem. Phys. 127, 114105 (2007)
# URL: http://link.aip.org/link/?JCP/127/114105
# DOI: 10.1063/1.2770708

and the GTH potentials.

I also investigated two other basis sets TZVP and TZV2PX the behaviour is the 
same.. just the energies different as expected...


 Without Questions there are no Answers!
  Alin Marin ELENA
  Advanced Molecular Simulation Research Laboratory
  School of Physics, University College Dublin
  Ardionsamblú Móilíneach Saotharlann Taighde
  Scoil na Fisice, An Coláiste Ollscoile, Baile Átha Cliath


[attachment "blyp.eps" removed by Jürg Hutter/at/UZH]
[attachment "hcth120.eps" removed by Jürg Hutter/at/UZH]
[attachment "pbe.eps" removed by Jürg Hutter/at/UZH]
[attachment "inputs.tar" removed by Jürg Hutter/at/UZH]
[attachment "signature.asc" removed by Jürg Hutter/at/UZH]

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