AMBER Archive (2009)

Subject: Re: [AMBER] Equilibrium bond lengths and angle values

From: FyD (fyd_at_q4md-forcefieldtools.org)
Date: Fri Apr 24 2009 - 16:05:42 CDT

Dear Dmitri,

> I parametrize new rather simple ligand for MD calculation.
> So first of all I`ve optimized geometry and got RESP charges using
> ab initio QM-calculations. Then I`ve chosen parameters for bonds and angles
> by analogy with similar ones reproduced
> in gaff.dat file. And at this point my question has arisen.
> Is it appropriate to use equilibrium bond lengths and angle values from
> gaff.dat file or it's better to use
> equilibrium values obtained from my QM geometry optimization?

Bond & angle equilibrium values are important to get a good
conformation representation. Taking equilibrium values for a new
chemical group from X-ray structures or from ab initio data obtained
using a high level of theory is widely used.

regards, Francois

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