Convergence problems with Au cluster


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Dear NWChem users and developers,
I have some problems in reaching convergence with a pretty simple calculation on an Au20 cluster.
The geometry should reproduce that of the bulk gold, so I would expect to achieve fast convergence in an energy dft run. But the calculation does not converge.
I am using lanl2dz_ecp basis set (common in literature) with effective core potential.
I tried to vary the damping factor and I increased it up to 99, but still it does not converge, even after thousands of iterations.

Here is the input file (a part from the geometry)

basis spherical
  Au library lanl2dz_ecp
end
ecp
  Au library lanl2dz_ecp
end

dft
  iterations 990
convergence damp 99
convergence ncydp 990
grid fine
direct
noio
end

task dft energy

Any suggestion on how to overcome this problem? Does anyone ever face the same problem?
Thanks a lot

Alessandro