Energy of atomic oxgyen and smearing

[Natalie Austin]

Hello,

I wanted to calculate the atomic energy of oxygen. I used the CP2K tutorial 
for GEO_OPT of H2O as an example to generate the input file.  What I 
noticed is that the energy calculation for atomic did not converge after 
500 SCF steps if I did not use smearing. Would anyone be able to explain 
why this is? Because I thought for such a small atom smearing would not be 
necessary. The energy for atomic oxygen also converged when I used the OT 
method but I thought it best to use diagonalization to keep consistent with 
the input I use for calculations on my metal systems. 
  
This is what I believe is the relevant part of the input form the 
calculation that converged. I indicated which lines were omitted from the 
calculation that did not coverge: 
&FORCE_EVAL
  METHOD QS
  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    &MGRID
      CUTOFF 400
      REL_CUTOFF 60
      NGRIDS 4
    &END MGRID
    &QS
       EPS_DEFAULT 1.0E-14
       MAP_CONSISTENT
    &END QS
  &SCF
     SCF_GUESS  ATOMIC
     EPS_SCF 1.0E-7
     MAX_SCF 500
     ADDED_MOS  200                                       *Added MOS was 
omitted in the calculation that did not converge.* 
     CHOLESKY INVERSE
     &SMEAR  ON
         METHOD FERMI_DIRAC
         ELECTRONIC_TEMPERATURE [K] 700     * This smear section was 
omitted in the calculation that did not converge. *
     &END SMEAR
     &DIAGONALIZATION
          ALGORITHM STANDARD
     &END DIAGONALIZATION
     &MIXING
          METHOD BROYDEN_MIXING
          ALPHA   0.1
          BETA    1.5
          NBROYDEN  8
     &END MIXING
  &END SCF
    &XC
      &XC_FUNCTIONAL PBE
      &PBE
      PARAMETRIZATION REVPBE
      &END PBE
      &END XC_FUNCTIONAL
      &VDW_POTENTIAL
         DISPERSION_FUNCTIONAL PAIR_POTENTIAL
         &PAIR_POTENTIAL
           TYPE DFTD3
            REFERENCE_FUNCTIONAL PBE
            CALCULATE_C9_TERM .TRUE.
            PARAMETER_FILE_NAME dftd3.dat
            R_CUTOFF 15.0
            VERBOSE_OUTPUT .TRUE.
         &END PAIR_POTENTIAL
      &END vdw_POTENTIAL
    &END XC
UKS .TRUE.
MULTIPLICITY 3


Any help with this would be appreciated. 
Thanks

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