Yes, there are (or can be) big differences, in my opinion.
Additionally, the level of QM used makes a significant difference. The
conventional wisdom is that you should use whatever charges the force
field you are using was parameterized with (in this case probably RESP
HF 6-31G* charges, or (perhaps) RESP AM1-BCC charges) so that errors
will cancel and so on. Generally this is probably a good idea unless
you have some good reason for doing otherwise, or want to explore what
happens if you do otherwise.
David
On 4/4/06, Jianzhong Liu <zhong.udel.edu> wrote:
> Dear Amber users,
>
> I just wondering why we don't use Chelpg or MK to calculate the charge of
> our molecular system since they also produce charges fit to the
> electrostatic potential at points selected.
>
> Are there any difference?
>
> Thanks,
>
> Jianzhong Liu
>
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Received on Wed Apr 05 2006 - 06:07:08 PDT