energy convergence question

Alin Marin Elena alinm... at
Wed Aug 31 11:05:50 UTC 2011

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:
# 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

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