atomic C does not converge with nolevelshifting


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Hello Nwchem users

I am trying to converge the SCF of atomic carbon with nolevelshifting as I want to compare these energies finally with smeared metallic cluster calculations. Both the gas phase and solvent phase did not converge for specified # iterations upto 3000. I tried different strategies (damping, cgmin, input vectors from scf/b3lyp for my pbe96 calculation) for obtaining convergence but it fails always. However, with default levelshifting it converges fine. Below is my input file. Thank you for any help.

echo

start cluster
geometry autosym
C 0 0 0
end


basis "ao basis" cartesian
C library 6-311G** file /usr/local/NWChem/data/libraries/
end

dft
iterations 1000
direct
mult 1
XC xpbe96 cpbe96
convergence ncyds 1000 nolevelshifting
end

DRIVER
XYZ a.xyz
MAXITER 500
END

cosmo
dielec 80.4
solvent water
do_cosmo_smd true
end


set cosmo:map cosmo-bondi.par
task dft