After facing problem with convergence of RO-B3LYP for anion-radical of 2-nitropropane in 6-31++G** basis, ( http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C325be7cdbHyz-9140-111-00.htmhttp://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C325be7cdbHyz-9140-111-00.htm ) I check if this problem appears with simpler systems - and it does.
First, I check nitromethane radical-anion, and problem does exist for both possible conformation - with one CH-bond eclipsing N-O bond (a minimum for neutral nitromethane for B3LYP/6-31++G** and MP2/6-31++G**, but transition state for HF/6-31++G** ) and with one C-H bond perpendicular to nitro group (minimum for HF/6-31++G**)
Second, I replaced methyl group for hydrogen atom - the simplest system still cause the same problem, no convergence of SCF at the first cycle.
Input file for H-NO2 is attached
Please, give advice how to cope with this problem, I'm quite interested in comparision of a series of radical-anion with NO2-moiety
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[ HNO2-radan_RO-B3LYP.inp ] input-file for H-NO2 radical-anion