Dear David,
Thank you very much for your help.
As per the literature am following , it is mentioned that the bond distance used is 0.7 Angstrom. Where do I incorporate the bond distance parameter in the topology file? The problem am facing is that , I am not very clear as to if the distance is between the two Hydrogen atoms of btween the dummy atom and each of the Hydrogen atoms in either side, in which case the total distance becomes 1.4 A. When i mention the bond distance in the topology file , should it be placed under Bond or constraint?


Thank you,
Jyotsna


Re: [gmx-users] H2 topology
David van der Spoel
Mon, 01 Feb 2010 04:02:06 -0800

On 2/1/10 10:57 AM, 011013021-Jyotsna wrote:
Dear all,

I want to run a simulation for an enzyme. It demands me to incorporate a Molecular hydrogen Topology with a dummy atom in between in the simulation in order to study the path of hydrogen in it.The problem is , the topology file I built induces many errors when i come to the energy minimization step. The version of gromacs I am using is 4.0. The
topology file I built is as follows



[ moleculetype ]
;name nrexcl
H2 3

[ atoms ]
; nr type resnr residu atom cgnr charge mass ; total charge
1 H 1 H2 H1 1 0.475 1.00800 ; 0.00
2 H 1 H2 H2 1 0.475 1.00800 ; 0.00
3 DUM 1 H2 DUM 1 -0.950 0.000

[ virtual_sites2 ]
; Site from funct a
3 1 2 1 0.7439756


When ever I insert the hydrogen+dummy atom topology in the protein's .gro file, an error is generated regarding mismatch of residues or the
dummy atom having mass 0 .

I would be really grateful if anyone could provide me the hydrogen
molecule topology and give some pointers towards it.


Please print the error message in your mail.

Topology look OK, but you need to add a bond or constraint. Also the constant probably has to be 0.5 since you want the vsite in the center of the two atoms.


Thank you,

Jyotsna


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