Discussion:
[gmx-users] Bonds missing in VMD visualization
Andreas Kring
2008-09-01 13:45:30 UTC
Permalink
Hello,

I have run an MD simulation of 1000 1,1,1-trichloroethane molecules and
it all worked nicely. But when I try to visualize the trajectory file in
VMD some of the C-Cl bonds are missing (although all the atoms appear on
the screen - only bonds are missing)?

Can I do anything to fix this?

/Andreas
Diego Enry
2008-09-01 14:51:26 UTC
Permalink
VMD computes distances between pairs of atoms to "draw" a bond. So I
think your atoms are too distanced from each other.
Check the bond distribution during MD and compare with your topology.
C-CL should be around 1.76A.
VMD will not show this bond if, in the REFERENCE frame (the .gro/pdb
you open before the .xtc/.trr), this distance is greater than 2.0A.
Post by Andreas Kring
Hello,
I have run an MD simulation of 1000 1,1,1-trichloroethane molecules and it
all worked nicely. But when I try to visualize the trajectory file in VMD
some of the C-Cl bonds are missing (although all the atoms appear on the
screen - only bonds are missing)?
Can I do anything to fix this?
/Andreas
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--
Diego Enry B. Gomes
Laborat?rio de Modelagem e Dinamica Molecular
Universidade Federal do Rio de Janeiro - Brasil.
Andreas Kring
2008-09-02 08:59:54 UTC
Permalink
Post by Diego Enry
VMD computes distances between pairs of atoms to "draw" a bond. So I
think your atoms are too distanced from each other.
Check the bond distribution during MD and compare with your topology.
C-CL should be around 1.76A.
In 1,1,1-trichloroethane the C-Cl bond distance should be around 1.81A.
I checked the C-Cl bond distances using g_bond and this give a nice
Gaussian distribution around 1.81A (which matches what is in the
topology file).
Post by Diego Enry
VMD will not show this bond if, in the REFERENCE frame (the .gro/pdb
you open before the .xtc/.trr), this distance is greater than 2.0A.
All bond distances are less than 2.0A, but VMD still does not draw a bond?

Is there anything else I can try?

/Andreas
Diego Enry
2008-09-02 14:59:59 UTC
Permalink
So I was testing on VMD the C-CL bond distance to draw a bond.
Actually, the limit was a disturbing 1.80A ! So close to the 1.81A you
need :(

Solutions !

1) Use "dynamic bonds representation" and set the cut-off to 1.81 or more

2) Find where VMD sets it's standard cutoff for bonds and set it to
1.81 or more forever.

3) VMD FAQ solution is to make a .PSF (topology) to solve this
problem. ( You will only need the bond list )
http://www.ks.uiuc.edu/Research/vmd/allversions/vmd_faq.html

How to write a .PSF file
http://www.ks.uiuc.edu/Training/Tutorials/namd/namd-tutorial-unix-html/node21.html
Post by Diego Enry
VMD computes distances between pairs of atoms to "draw" a bond. So I
think your atoms are too distanced from each other.
Check the bond distribution during MD and compare with your topology.
C-CL should be around 1.76A.
In 1,1,1-trichloroethane the C-Cl bond distance should be around 1.81A. I
checked the C-Cl bond distances using g_bond and this give a nice Gaussian
distribution around 1.81A (which matches what is in the topology file).
Post by Diego Enry
VMD will not show this bond if, in the REFERENCE frame (the .gro/pdb
you open before the .xtc/.trr), this distance is greater than 2.0A.
All bond distances are less than 2.0A, but VMD still does not draw a bond?
Is there anything else I can try?
/Andreas
_______________________________________________
gmx-users mailing list gmx-users at gromacs.org
http://www.gromacs.org/mailman/listinfo/gmx-users
Please search the archive at http://www.gromacs.org/search before posting!
Please don't post (un)subscribe requests to the list. Use the www interface
or send it to gmx-users-request at gromacs.org.
Can't post? Read http://www.gromacs.org/mailing_lists/users.php
--
Diego Enry B. Gomes
Laborat?rio de Modelagem e Dinamica Molecular
Universidade Federal do Rio de Janeiro - Brasil.
Andreas Kring
2008-09-03 11:05:22 UTC
Permalink
Thank you for solution suggestions!

Solution 1 worked out just fine. After a little Goolgeing it seemed as
if solution 2 requires modification of the VMD source code. Solution 3
also looks attractive - I'll have a closer look at this later on...

/Andreas
Post by Diego Enry
So I was testing on VMD the C-CL bond distance to draw a bond.
Actually, the limit was a disturbing 1.80A ! So close to the 1.81A you
need :(
Solutions !
1) Use "dynamic bonds representation" and set the cut-off to 1.81 or more
2) Find where VMD sets it's standard cutoff for bonds and set it to
1.81 or more forever.
3) VMD FAQ solution is to make a .PSF (topology) to solve this
problem. ( You will only need the bond list )
http://www.ks.uiuc.edu/Research/vmd/allversions/vmd_faq.html
How to write a .PSF file
http://www.ks.uiuc.edu/Training/Tutorials/namd/namd-tutorial-unix-html/node21.html
Post by Diego Enry
VMD computes distances between pairs of atoms to "draw" a bond. So I
think your atoms are too distanced from each other.
Check the bond distribution during MD and compare with your topology.
C-CL should be around 1.76A.
In 1,1,1-trichloroethane the C-Cl bond distance should be around 1.81A. I
checked the C-Cl bond distances using g_bond and this give a nice Gaussian
distribution around 1.81A (which matches what is in the topology file).
Post by Diego Enry
VMD will not show this bond if, in the REFERENCE frame (the .gro/pdb
you open before the .xtc/.trr), this distance is greater than 2.0A.
All bond distances are less than 2.0A, but VMD still does not draw a bond?
Is there anything else I can try?
/Andreas
_______________________________________________
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Please don't post (un)subscribe requests to the list. Use the www interface
or send it to gmx-users-request at gromacs.org.
Can't post? Read http://www.gromacs.org/mailing_lists/users.php
--
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Andreas Kring, Ph.D.-student
University of Copenhagen
Niels Bohr Institute
Universitetsparken 5
DK-2100 Copenhagen
Denmark

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