Thank you for your advice, Christoph. 

How do you recommend I use harmonic potentials for a CG simulation? I have 
the bond.dist.new histogram after I did my mapping, I can use the modal 
bond length I obtained from that. However, what can I use as my spring 
constant? 

Using csg_boltzmann on my bond distribution, I obtained the table at 298 K 
and set bond, however, the table that was created started at 0.19 nm. My 
question is, when performing a boltzmann inversion on the bond 
distribution, how do we treat the bins with a height of 0? should the 
number at that point simply be inf? 

This is my mapping file, just to be complete:
<cg_molecule>
<name>BNZ</name> <!-- the name of the molecule after mapping--> 
<ident>UNK</ident> <!-- name of the actual atom --> 
<topology>
<cg_beads>
<cg_bead>
<name>B1</name>
<type>CG</type>
<symmetry>1</symmetry>
<mapping>A</mapping> 
<beads>
1:UNK:C00 1:UNK:C01 1:UNK:C02 1:UNK:H06 1:UNK:H07 1:UNK:H08 
</beads> 
</cg_bead>

<cg_bead> 
<name>B2</name>
<type>CG</type>
<symmetry>1</symmetry> 
<mapping>A</mapping> 
<beads>
1:UNK:C03 1:UNK:C04 1:UNK:C05 1:UNK:H09 1:UNK:H0A 1:UNK:H0B
</beads>
</cg_bead>
</cg_beads>

<cg_bonded> 
<bond>
<name>bond</name> 
<beads>
B1 B2
</beads>
</bond>
</cg_bonded>
</topology>

<maps>
<map>
<name>A</name>
<weights>12.0110 12.0110 12.0110 1.0080 1.0080 1.0080</weights>
</map>
</maps>
</cg_molecule>

I used this file as my mapping file when I executed:
csg_boltzmann --top topol.tpr --trj trajectory.trj --cg bezene.xml
tab set T 298
tab set scale bond 
tab table_b1.xvg *:bond:*
On Monday, April 5, 2021 at 9:09:15 PM UTC-4 Christoph Junghans wrote:

> On Mon, Apr 5, 2021 at 2:20 PM Satyen Dhamankar <[email protected]> wrote:
> >
> > Hello,
> >
> > I am performing a coarse-grained simulation of benzene, where I am 
> converting C6H6 into two beads. Where each bead is essentially C3H3, and 
> they are connected by a bond.
> >
> > I want to perform IBI on this coarse-grained simulation using votca and 
> gmx, but I am having some problems.
> >
> > The command I am running is:
> > csg_inverse --options settings.xml
> >
> > I am getting an energy divergence (blows up to infinity) when votca runs 
> mdrun. This is the error I see in my inverse.log file:
> >
> > Program: gmx mdrun, version 2019.6
> > Source file: src/gromacs/mdlib/sim_util.cpp (line 752)
> > MPI rank: 1 (out of 6)
> > Fatal error:
> > Step 0: The total potential energy is inf, which is not finite. The LJ 
> and
> > electrostatic contributions to the energy are inf and 0, respectively. A
> > non-finite potential energy can be caused by overlapping interactions in
> > bonded interactions or very large or Nan coordinate values. Usually this 
> is
> > caused by a badly- or non-equilibrated initial configuration, incorrect
> > interactions or parameters in the topology.
> > For more information and tips for troubleshooting, please check the 
> GROMACS
> > website at http://www.gromacs.org/Documentation/Errors
> >
> > I am running a minimization script, but I don't see why energy is 
> blowing up.
> >
> > I also am unsure of what the table_b1.xvg and table_a1.xvg files are 
> for. I naively got these files from the hexane tutorial. What are these 
> files for? How do I make them?
> These two tables are for the bonded interactions, they are just
> boltzmann-inverted tables from the bonded distributions (do that by
> hand or use csg_boltzmann).
> You could also use harmonic potentials as a start to make your life easier.
>
> Christoph
> >
> > I have attached my grommp.mdp, conf.gro, settings.xml, topol.top and 
> tables files.
> >
> > Any advice you have would be appreciated!
> >
> >
> > --
> > Join us on Slack: https://join.slack.com/t/votca/signup
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> .
>
>
>
> -- 
> Christoph Junghans
> Web: http://www.compphys.de
>

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