[QE-users] C anion SCF convergence

[Giuseppe Mattioli]

Dear Aulia Sukma Hutama
Please look into the
your_path_to_QE/PW/examples/example05
directory. You will find suggestions for the calculation of isolated  
(neutral) atoms. Remember also that due to the strong delocalization  
errors of LDA and GGA xc functionals, negative ions may have unbound  
states, that is, excess electrons fully delocalized across the plane  
wave basis set rather than localized on a given atomic orbital.
HTH
Giuseppe

Quoting Aulia Sukma Hutama <hutamaaulia at gmail.com>:

> Dear All,
>
>
> I am unable to achieve SCF convergence of simple C- anion in its quartet
> ground state. It appears there is an energy oscillation from the output
> file so I terminated the calculation. I have tried to change the
> mixing_beta value, mixing_mode, starting_magnetization value but there
> seems no improvement on the results. Does anyone have any idea how to solve
> this problem or did I make a mistake when trying to calculate anion?
>
> Below are my input files for this calculation and the few last lines of the
> output.
>
> ================================================================
>
> &CONTROL
>   calculation = "scf",
>   pseudo_dir  = "/media/metal/Work/qe_pseudo",
>   prefix      = "C"
> /
> &SYSTEM
>   ibrav       = 0,
>   nat         = 1,
>   ntyp        = 1,
>   ecutwfc     = 45.0,
>   ecutrho     = 400.0,
>   nspin = 2,
>   tot_charge = -1
>   starting_magnetization(1)=1.0
>   tot_magnetization = 3.0
>   starting_charge(1) = -1
> /
> &ELECTRONS
>   conv_thr    = 1.D-6,
> /
> CELL_PARAMETERS angstrom
> 20.0  0.0  0.0
>  0.0 20.0  0.0
>  0.0  0.0 20.0
> ATOMIC_SPECIES
> C  1.0  C.pbesol-n-kjpaw_psl.1.0.0.UPF
> ATOMIC_POSITIONS crystal
> C     0.500000000         0.5000000         0.5000000
> K_POINTS gamma
>
> ======================================================================
>
>     iteration # 55     ecut=    45.00 Ry     beta= 0.70
>      Davidson diagonalization with overlap
>      c_bands:  1 eigenvalues not converged
>      ethr =  2.60E-06,  avg # of iterations = 10.5
>
>      total cpu time spent up to now is      758.7 secs
>
>      total energy              =     -17.72466906 Ry
>      Harris-Foulkes estimate   =     -17.72579866 Ry
>      estimated scf accuracy    <       0.85267583 Ry
>
>      total magnetization       =     3.00 Bohr mag/cell
>      absolute magnetization    =     3.00 Bohr mag/cell
>
>      iteration # 56     ecut=    45.00 Ry     beta= 0.70
>      Davidson diagonalization with overlap
>      c_bands:  1 eigenvalues not converged
>      ethr =  2.60E-06,  avg # of iterations = 11.5
>
>      total cpu time spent up to now is      773.3 secs
>
>      total energy              =     -17.70913541 Ry
>      Harris-Foulkes estimate   =     -17.72533527 Ry
>      estimated scf accuracy    <       1.03751336 Ry
>
>      total magnetization       =     3.00 Bohr mag/cell
>      absolute magnetization    =     3.00 Bohr mag/cell
>
> ==================================================================
>
> Aulia Sukma Hutama



GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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E-mail: <giuseppe.mattioli at ism.cnr.it>