Re: [AMBER] 1D-RISM: "ERROR> RXRISM: reached steps limit Maxstep=10000 STOP 1"

From: PRITI ROY <>
Date: Fri, 18 May 2018 10:52:51 +0530

Dear David,

Thank you for such an effort and giving your valuable comment.

I have searched in the literature about Di-electric constant of TIP3P water
model and I got to know this model has higher value than other simple
3-point models. Here is one of the reference: (The reason for using
such an high value)

In my protein water complex system I have only Na+ ions, that's why I took
only this ion.

I figure out that main failure of my calculation is the density. I
rechecked the density which is around 0.96 gm/cm^3. Now I can run the
1D-Rism using the Na+ and water using the mentioned density.


On Thu, May 17, 2018 at 9:41 PM, David A Case <>

> On Thu, May 17, 2018, PRITI ROY wrote:
> >
> > I want to calculate the solvation free energy of my system through
> > and this is my first time approach of this method. Before going to this
> > step I need to get bulk water information which done by 1D-RISM. I have
> > used TIP3P water model with Na+ ions. My input file is as follows:
> As pointed out in a separate email, the size of the grid needed for a
> bulk (rism1d) simulation is not related to the eventual size of your
> 3drism box.
> You can see sample rism1d inputs in $AMBERHOME/AmberTools/test/rism1d:
> try to build off of those.
> Your input file has some very odd choices: first you have water and
> sodium ions, but no anions. While this is not technically impossible,
> it doesn't make physical sense, and is almost certainly will cause all
> kinds of problems, especially for someone new to these calcualations.
> Your solvent needs to be electrically neutral.
> > TEMPER=310, DIEps=95.0,
> This is a very high dielectric constant: are you sure this is what you
> want?
> > units='g/cm^3'
> > DENSITY=2.85,
> > MODEL="../TP3.mdl"
> Also a very odd density. Again, are you sure this is what you want?
> I don't think one would expect our simple models of water to work at all
> well under such conditions, even if you could get the RISM equations to
> converge.
> ....dac
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Received on Thu May 17 2018 - 22:30:03 PDT
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