On Mon, Aug 6, 2012 at 10:53 AM, Igor Pochorovski
<igor.pochorovski.gmail.com> wrote:
> Dear amber users,
>
> I would like to perform AMBER GAFF simulations of supramolecular systems in
> organic solvents like chloroform, THF, or benzene. The standard method for
> charge derivation in GAFF is RESP HF/6-31G(d), which is known to
> overestimate dipole moments. While this is regarded to be advantageous for
> simulations in water, I am not sure whether it is the best method for
> simulations in organic solvents. On the other hand I obtained topologies of
> the solvent molecules from virtualchemistry.org whose charges have been also
> determined using a method which gives similar charges as HF/6-31G(d).
> Do you think it is OK to use HF/6-31G(d) or would it be better to use, for
> example, B3LYP/cc-pVTZ that is known to reproduce gas phase charges?
This, unfortunately, depends on each particular solvent. HF somewhat
overestimates partial charges. If this everestimation is in agreement
with the dipole moment increase due to electronic polarization in
condensed phase of the solvent/solution, than the method works nice.
If not, than large discrepancy can be expected.
--
Dr. Vitaly V. Chaban, 430 Hutchison Hall
Dept. Chemistry, University of Rochester
120 Trustee Road, Rochester, NY 14627-0216
THE UNITED STATES OF AMERICA
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Received on Mon Aug 06 2012 - 08:00:03 PDT
