Hi Hansly,
The error message:
This type of error is most commonly associated with calculations not reaching
convergence criteria
is in this case a complete red herring. The reason you get this message is because the energy calculation failed and this fact is passed up to the gradient or hessian driver. That routine only knows the energy evaluation failed but not really why. It then pronounces this wild guess that most likely something did not converge.
In actual fact in this case there is an entirely different problem. The problem is that the finite difference hessian code cannot use symmetry (the finite difference gradient code actually can). So when you hit the hessian driver it turns all symmetry off. However, you used symmetry to specify the target state of interest. With all symmetry gone TCE all of a sudden can no longer identify the state you are after and instead it now reports this a failure of the energy code back to the gradient and hessian drivers (which then confuse it for a convergence problem).
So the fix for this problem is to set the whole calculation up without symmetry (e.g. specify symmetry c1 in the geometry block).
I hope this helps,
Huub
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