Fractional occupation


Just Got Here
Hello,

I am new to nwchem and want to calculate the energy of a single C-atom in a closed shell dft calculation with fractional occupation of each of the three 2p orbitals with a value of 0.66666666.

I tried to achieve this by smearing, but for every value I choose in the smearing Gaussian I achieved a different result (and even much lower energies could be achieved what I actually don't understand). I also tried with the rabuck option, but the calculation was not converging. What is the right way do do this ?

My input file is

title "C_pv3z"
geometry units au
C      0.0 0.0 0.0
end
basis
C library aug-cc-pvtz 
end
dft
grid xfine
smear 0.001
xc slater perdew81
iterations 150
# convergence rabuck 30
end
TASK DFT

Thanks for your answers

Volker

Forum Vet
need to use symmetry
Volker,
The only ingredient that you are missing in your input file is symmetry.
Unfortunately NWChem 1) does not have spherical symmetry (the one appropriate for atoms) and 2) we leave c1 as the point group for atoms.
The trick is to assign oh as a point group, then you will get the desired (and correct) 2/3 occupation of the p orbitals;
have a look at the input file at the bottom.
Cheers, Edo

title "C_pv3z"
geometry
C 0.0 0.0 0.0
symmetry oh
end
basis
C library aug-cc-pvtz
end
dft
grid xfine
smear 1d-6
xc slater perdew81
end
TASK DFT

Just Got Here
Thanks
Thanks a lot, worked perfectly

Volker


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