Regarding CG approach to be used for deriving the potential for Homopolymer Electrolytes system

[Sanjeet Singh]

Hello Everyone,

I would like to derive the CG potential for a Homopolymer Electrolyte system. But, I am confused that which approach among IBI, FM or REM would be better. 

I know that IBI is not good for dilute system, considering the number of ion pairs present in the system compared to the polymer.

Any suggestion would be of great help.

Thank you.

Sanjeet

[Christoph Junghans]

On Sat, Feb 18, 2023 at 8:26 PM Sanjeet Singh <sanje...@gmail.com> wrote:
>
> Hello Everyone,
>
> I would like to derive the CG potential for a Homopolymer Electrolyte system. But, I am confused that which approach among IBI, FM or REM would be better.
>
> I know that IBI is not good for dilute system, considering the number of ion pairs present in the system compared to the polymer.

You are right, getting enough statistics for IBI in dilute systems can
be cumbersome. I would try FM for the ions.
And you can always combine it with an IBI potential for the polymer.

Christoph

>
> Any suggestion would be of great help.
>
> Thank you.
>
> Sanjeet
>

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--
Christoph Junghans
Web: http://www.compphys.de

[Sanjeet Singh]

Dear Christoph,

Thank you for your reply.

I have another query though. In the VOTCA tutorial for liquid hexane with FM for non-bonded interactions only, it is mentioned that we have to exclude all the intramolecular interactions also in addition to the all bonded interaction. I am not getting why we need to exclude the intramolecular nonbonded interaction also? Because, I think these interactions needs to be accounted in the nonbonded interactions part. 

Can you please clarify me on this.

Thank you.

Sanjeet

[Christoph Junghans]

On Wed, Feb 22, 2023 at 7:03 AM Sanjeet Singh <sanje...@gmail.com> wrote:
>
> Dear Christoph,
>
> Thank you for your reply.
>
> I have another query though. In the VOTCA tutorial for liquid hexane with FM for non-bonded interactions only, it is mentioned that we have to exclude all the intramolecular interactions also in addition to the all bonded interaction. I am not getting why we need to exclude the intramolecular nonbonded interaction also? Because, I think these interactions needs to be accounted in the nonbonded interactions part.

The coarse-grained topology has #excl of 3
(https://github.com/votca/votca/blob/master/csg-tutorials/hexane/ibi_nonbonded/topol.top#L13)
hence the A and B beads within a CG molecule don't interaction via
non-bonded interaction and so are fully covered by the bonded
interaction, which then means you need to exclude them for the
non-bonded interaction calculation.
I think this should be explained in more detail here:
http://dx.doi.org/10.1002/mats.201100011

However the setup of #excl of 3 is a gromacs inspired, and you could
certainly build a cg model where the A and B beads inside a molecule
also interact via non-bonded interactions. This is more common when
using lammps though.

Christoph

> To view this discussion on the web visit https://groups.google.com/d/msgid/votca/56b684e7-8e04-4f49-8d74-e17dd24cfd73n%40googlegroups.com.

[Sanjeet Singh]

Dear Christoph,

Thank you for the clarification.