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olgerdovich
olgerdovich@yandex.ru

I'm a newbie in computational chemistry, but with some diligence I started learning it in relation to quite simple chemical tasks from the field of nitrocompounds and I've stumbled upon several problems. First of them is the subject of this post.

When I ran geometry oprimization with hessian computing for 2-nitropropane, first at HF/6-31++G** and then at B3LYP/6-31++G** level (with starting geometry form HF-calculation), I found no problem, there were convergences to ground states.

Next I ran geometry oprimization with hessian computing for 2-nitropropane radical anion at ROHF/6-31++G** and once again found no trouble. It was surprising to me that some vibrations were very intense in IR to the contrary to their analogues for neutral particle, but I assumed that it was rather reasonable taking into account concomitantly changed spin and charge. The resulting species was in ground state again.

But when I started geometry oprimization (with hessian computing) for 2-nitropropane radical anion at B3LYP/6-31++G** level (with starting geometry form ROHF-calculation), run crashed on the first iteration cycle for SCF even when I indicate "maxit=99" (at higher values compilator returned error, it seemed like maxit should nor be larger then NSTEP=100 in $STATPT or just larger then 100): Energy changes started to oscillate and resulted in no convergence.

Output-file is attached

What may I adjust in my input to get result?
Hoe can I take into account electron correlation for anion-radical like the above in general?

Thank you in advance

This message contains the 45 kb attachment [ 2-NP-radan-RO-B3LYP-edited.txt ] edited out-file for crashed RO-B3LYP