PMEGridSize and parameters controlling electrostatic interactions.

From: Dawid das (
Date: Sat Jan 24 2015 - 13:48:44 CST

Dear NAMD experts,

I was doing MD simulation on a small system and I used following parameters:

Pme on
PmeGridSizeX 48
PmeGridSizeY 48
PmeGridSizeZ 96

switching on
switchDist 10
cutoff 12
pairlistdist 14
margin 3

Everything went fine, until I made my system bigger, so I had to change PME
grid sizes to:

PmeGridSizeX 96
PmeGridSizeY 96
PmeGridSizeZ 244

Now when I try to heat up my system I get following error at 116 K:

FATAL ERROR: Low global exclusion count! (1086603 vs 1086604) System
unstable or pairlistdist or cutoff too small.

So my question is if there is any relationship between PmeGridSize and
electrostatic parameters values in a sense that I should change the latter
in this case?
Or perhaps I shall not increase PmeGridSize, but *PMEGridSpacing *instead?

Best wishes,

Dawid Grabarek

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