Re: [AMBER] compute RESP charges

From: Dr. Anselm Horn <>
Date: Thu, 10 Nov 2016 11:21:31 +0100

Dear asdda asa,

> Can we compute RESP charges on compound which geometry-optimized on the
> 3-21G* basis set of the Hartree-Fock?

short answer: yes.

long answer:
Atomic charges per se are a quantum chemical construct, there are no
"correct" charges. In MD simulations, atomic charges are used to model
the electrostatic interaction between atoms.
In Amber, these charges are derived following a rather standardized
protocol, e.g. RESP charges from a HF/6-31G(*) electron density of one
or more structures for ff99SB or FF14SB.
(cf F.-Y. Dupradeau's tools )

However, the choice of the right structure(s) is up to you; often one
would use a QM geometry optimization at the same level as the RESP
charge derivation, but a different approach is also possible. Thus, you
may obtain "reasonable" charges from a 6-31G(*) electron density
computed for your 3-21G* optimized geometry; but if it is
computationally feasible, I'd suggest a re-optimization of your
structure with the larger 6-31G(*) basis set.



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Received on Thu Nov 10 2016 - 02:30:03 PST
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