2013/9/30 Chandan Choudhury <[email protected]>:
> Dear votca users,
>
> I am iterating the non-bonded part of the polymer (with following sequence:
> A1-B1-C1-B2-D1-B3-C2-B4-D2-B5-C3-E1). In step_001, my observations are
> following:
>
> csg_stat uses the following command to compute the distributions :
>
> csg_stat --nt 8 --options
> /data/home/chandan/Documents/votca/polycarbonate/trimer/mapping_II/re/ibi/nb/B_D/settings.xml
> --top topol.tpr --trj traj.xtc --begin 20 --first-frame 0
>
> I obtain the distributions in B-D.dist.new file. Here in settings.xml, the
> min is 0.37
>
> When, I change the min to 0. It gives the exact distribution.
>
> But, when I try to include the information of all the other bonded and
> non-bonded interaction (min=0.0 and max values), then I need to use a
> mapping file (attached).
> csg_stat --nt 8 --options settings_csg_stat.xml --top ../topol.tpr --trj
> ../traj.xtc --begin 20 --first-frame 0 --cg ../../pc_new_cg.xml
>
> Here, the setting contains all bonded and non-bonded part with min=0.0. The
> distribtution I obtain is B-D.dist_withpc-xml.new.
>
> I also tried the g_rdf tool (with nrexcl=3). The output file is B-D.rdf.xvg.
> Here the selection are between all B's and D's.
>
> It can be seen that the distribution obtained are different. On using
> coarse-grained xml and when I donot use it, the distributions are different.
> The gmx tool also gives the different result.
>
> Am I doing something wrong. I can suspect the problem might be in the cg
> mapping file. But, I am unable to locate it. Can some one help me.
>
> The trajectory and tpr is same for all the above commands.
The  trajectory is missing, just send a conf.gro. One frame will be
enough to check for the error.

These are two separate issues.

1.) The difference between g_rdf and csg_stat without mapping file
Could you check that all exclusion you expect, show up in:
$ csg_stat --top topol.tpr --execl
and compare to the exclusion in
$ gmxdump -s topol.tpr

2.) The difference between csg_stat with and without mapping file
For this you have to understand how exclusion in VOTCA.
If you don't specify a mapping file, exclusion are just read for the
topology (tpr).
If you specify a mapping file, exclusion are generated by VOTCA due to
the following rule.
Everything which is connected via a bond, angle or dihedral is excluded.
In your case to generate exclusion equivalent to nrexcl=3, you will
need add some extra dihedrals to the mapping file (with evaluating
them).

If you are unsure compare:
$ csg_stat --top topol.tpr --execl
with
$ csg_stat --top topol.tpr --execl --cg pc_new_cg.xml

We need to document that better, patch for the manual are welcome!
<https://code.google.com/p/votca/wiki/Manual>

Cheers,

Christoph
>
> Chandan
> --
> Chandan kumar Choudhury
> NCL, Pune
> INDIA
>
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-- 
Christoph Junghans
Web: http://www.compphys.de

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