CCL:G: Natural Resonance Theory Calculations

[Benjamin Stein <benjamin.w.stein~!~gmail.com>]

Hi Italo,

Unfortunately the NRT sometimes has a little trouble getting started. You can manually enter reference structures using the NRTSTR keyword; enter at least the parent NBO structure, and then maybe structures formed by a few leading delocalizations. If they were bad choices the NRT routine will let you know about secondary structures having higher weights than primary structures.

-Ben

On Jan 5, 2012, at 4:13 PM, Italo Anjos italocurvelo^gmail.com wrote:

Hello,

I' ve been running some NRT (Natural Resonance Theory) calculations using NBO 5.9/ Gaussian g09. For most compounds, analysis seem to be successful as they find many canonical structures and display their respective weightings. But for a few molecules, NBO seems unable to determine the resonance structures and output displays the following message:

No covalent reference structures found; abandon NRT analysis

All calculations were made for a set of sulphur-containing heterocyclic compounds. It seems odd that for some of them, NBO found dozens of canonical structures and it found none for the others.

Could anyone help me with this problem?

I appreciate any help.

Regards,

Italo