Author Topic: atomization energy of O2  (Read 5329 times)

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Offline marcindulak

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atomization energy of O2
« on: April 26, 2012, 12:34 »
Hi,

i'm trying to calculate O2 atomization energy (2*E(O)-E(O2)) with PBE, hgh pseudopotentials
(i assume ATK uses http://www.abinit.org/downloads/psp-links/psp-links/hgh).
I'm having troubles getting ~5.71 eV from atk-12.2.r1.622604e-linux64.bin,
the result I expect based on the calculations with ASE-3.6.0/abinit-5.4.4p::

  python `which ase` abinit molecule O2 O --unit-cell='14.00,14.01,14.02' \
         -l -p 'xc=PBE,ecut=1500,width=0.001,toldfe=1.0e-7,nstep=250,pps=hgh'
  python `which ase` abinit molecule O2 O -s

My ATK script is attached. Could you help me to find out what i'm doing wrong?
I have also additional questions:

1. the SCF with current script settings does not converge, and it seems I have to increase
    the electron_temperature to ~5K in order to make SCF converge. In principle i need to run at 0K,
    so i tried to reduce the electron_temperature in order to get 0 entropy::

      ncdump *.nc | grep "entropy ="

    0K seems not accepted::

      NL.ComputerScienceUtilities.Exceptions.NLValueError: The parameter, electron_temperature,
      must be a positive temperature quantity - e.g. 300*Units.Kelvin

2. how can i determine what electronic state i get? I have singlet and triplet methylene (CH2) molecules.
    LCAOCalculator does not seem to accept initial_spin parameter, so i'm thinking about BulkConfiguration
    in order to perform such calculations. What other things need to be adjusted in order to describe
    a molecule by BulkConfiguration?