I have been trying to run DFT calculations on partially fluorinated vanadyl napthalocyanine (527 electrons) and unfluorinated vanadyl phthalocyanine (295 electrons) (both C4v symmetry, enforced) using simple basis sets (3-21g or 6-31g) and B3LYP as an exchange functional. While my jobs are successful, all of the outputs have included "symmetry fudging" and warnings about the HOMO and LUMO being degenerate. Some of the jobs barely reach convergence after 120 iterations. What can I do to improve my calculations? I am already using simple basis sets, so should I switch to HF instead of DFT? Here is one of my VONc-F16 input file without the coordinates:
start voncfjob9
ECHO
ECCE_PRINT /dtemp/bock788/VONcF/VONcFjob9/eccejob9.out
charge 0
geometry units angstroms
[coordinates here]
symmetry c4v print
end
basis spherical
end
dft
mult 2
iterations 120
xc b3lyp
end
driver
maxiter 60
end
task dft energy
And here are some of the common warning messages in my output files:
Warning: spatial symmetry breaking in UKS: alpha = 2.15E-02
d= 0,ls=0.0,diis 2 -4860.6199036872 2.46E+01 5.32E-03 4.58E+01 21.7
Symmetry fudging
Warning: spatial symmetry breaking in UKS: alpha = 3.09E-02
d= 0,ls=0.5,diis 47 -4887.6388975884 -1.53E-06 1.64E-06 5.28E-06 189.5
4.72E-07 5.19E-06
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Warning - the HOMO and LUMO are degenerate and you are using symmetry.
This can lead to non-variational energies and poor convergence.
Modify the initial guess, or use an open-shell wavefunction, or turn
off symmetry.
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Thanks in advance, any help is greatly appreciated.
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