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

From: David A Case <>
Date: Wed, 1 Feb 2012 13:28:37 -0500

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 Wed Feb 01 2012 - 10:30:03 PST
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