Subject: Summary:Accuracy question

From: "Victor Anisimov" <[email-masked]>
Date: Fri, 12 Jul 2002 15:37:51 +0200

Dear CCLers,

A couple of days ago I asked a question:

> Based on my short investigation I could learn that HF/6-31G* is the most
> popular method for electrostatic parameter optimization in Amber, Charmm,
> OPLS and perhaps in other prominent force fields with the aim of the
> description of molecular electrostatic potential of protein systems.
>
> Here I'd like to ask experts in this field. Is it the correct conclusion I
> derived or perhaps other quantum-chemistry methods are more popular
> for the purpose of electrostatic parameters development, e.g. databases
> of ESP charges of amino acids or similar.

I have got two replies. Many thanks to Prof. Joгo Bosco Paraiso da Silva
and to Dr. E. Lewars for sharing their opinion.

The short summary is that HF/6-31G* is recommended for ESP charge
fitting. Nevertheless HF/3-21G is also in use for calculation of molecular
electrostatic potential of proteins and parameterization of the
electrostatic
components of the force field parameters.

Additionally I could dig up that there is some interest to electrostatic
property
calculations by density functional GGA methods employing Coulomb density
fitting procedure, although it is not clear how important (or non important)
are
errors due to not use of the explicit Hartree-Fock exchange.

Any comments a very welcome.

With best regards,
Victor.

--
Victor Anisimov
FQS Poland, Krakow

================================================
From: "Bosco" <[email-masked]>

>     Do you know the paper: M.D. beachy et al JACS, 119,5908-5920(1997).
> There you may find on page 5917 arguments why one should use HF/6-31G*
> charges on molecular parametrization process.

From: "elewars" <[email-masked]>

> I think it makes little difference whether you use HF/6-31G* or the faster
> HF/3-21G for electrostatic properties. Compare some test jobs. Since you
use
> programs like Amber and Charmm, I believe you are doing single-point
> calculations on geometries obtained by MM.