PC GAMESS/Firefly-related discussion club

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sanya
sanya@photonics.ru

First, my experience shows that it is better to turn SOSCF off on DFT runs.

Second, DFT is not good for open-shell systems (Ni²⁺ is d⁸, a difficult open shell case), so poor convergence is not surprising.

Third, are you sure you are interested in a system with charge +2, i.e., Ni²⁺...urea? For a neutral system SCF converges (with SOSCF=.f.) in less than 50 iterations.

>I have used $VEC from the same input but with MULT=1

Did your SCF converge for MULT=1 ICHARGE=2? I tried MULT=3 ICHARGE=0 and it converged. Unfortunately, the orbitals from these runs were poor guess for MULT=3 ICHARGE=2.

So, if you are sure you really need the system with Ni²⁺, you should use state-averaged MCSCF instead of DFT. It's a skilled work.