AMBER Archive (2003)

Subject: AMBER: Atomic charges and internal H-bond

From: Martin Lepsik (lepsik_at_marilyn.uochb.cas.cz)
Date: Tue Oct 07 2003 - 06:41:19 CDT

Dear AMBER community,
I am calculating partial charges on organic fragments via HF/6-31G* optimization and ESP and RESP fit. In some structures, there are internal H-bonds and the fit yields more negative charges on atoms involved in the H-bond than I expect (e.g.donor nitrogen -0.6).

Is this an artifact of the fit or does it reflect the electrostatic behavior of the H-bond? How shall I go on when I want to have this internal H-bond during dynamics?

For other structures, I optimized with dihedral restraints to avoid internal H-bonds. What cutoff for donor hydrogen-acceptor distance should be used so that the fit wouldn't be much influenced? Is there a study on the effect of the H-bonds on the quality of ESP fit?

Thank you in advance for your responses.

Regards,

Martin Lepsik

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