[gmx-users] partial charges leading to non-zero total charge/floating point arithmetic

Shayna Hilburg shilburg at mit.edu
Mon Apr 23 16:29:35 CEST 2018

Hi all,

I'm setting up a system and I am getting a non-zero total charge of
approximately 0.0002. I have several thousand ions in a system where the
cation is a single atom of charge +2, and then the anion is a CO3 molecule
(C with +1.3 and O with -1.1). If I change the partial charges to be full
charges (C with +1 and O with -1), there is no longer a non-zero total

According to the error documentation, I understand this is probably due to
floating point arithmetic, but I do not understand fully which calculation
might be causing it and what technique I should take to have a neutral
system. I am running in a low dielectric medium so I think the slight net
charge could be an issue. Any suggestions would be appreciated!


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