Re: [AMBER-Developers] non-neutral ethane from antechamber

From: Scott Brozell <sbrozell.rci.rutgers.edu>
Date: Tue, 28 Feb 2012 02:37:39 -0500

Hi,

qm2_print_charges.F90 has not been changed in the master branch;
was that because of some issue, like more testing needed,
or just an oversight ?

scott

On Fri, Feb 03, 2012 at 12:35:45PM -0700, Crowley, Michael wrote:
> Three decimals gives bad charges in the mol2 file. The charges do not
> match the ones from the other precisions, and the difference from zero of
> the total charge is in the 2nd digit, not the third.
>
> Any precision above 3 that gives consistent charges with different
> precisions that add to zero to the last digit.
>
> *** I suggest we change the precision from f14.3 to f14.5 at least ****
>
>
> On 2/1/12 11:28 AM, "David A Case" <case.biomaps.rutgers.edu> wrote:
> >On Tue, Jan 31, 2012, Crowley, Michael wrote:
> >
> >> I wonder if there is something wrong with either my approach or with the
> >> antechamber process.
> >> Something as simple as ethane gives charges that do not add to zero
> >> (+0.00200).
> >
> >The sqm program only prints Mulliken charges to three decimal places.
> >Then
> >when atom charges are symmetrized (so the equilvalent atoms have the same
> >charge), round-off errors can accumulate.
> >
> >Try changing the qm2_print_charges.F90 file to print an extra digit of
> >precision for the Mulliken charges. I'm guessing (hoping) that
> >antechamber
> >will pick that up, and you will get results closer to zero.
> >

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Received on Tue Feb 28 2012 - 00:00:02 PST
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