[gmx-users] Reg: Energy minimisation of hexane

[Mark Abraham]

----- Original Message -----
From: vinothkumar mohanakrishnan <kmvinoth at gmail.com>
Date: Wednesday, October 6, 2010 15:20
Subject: [gmx-users] Reg: Energy minimisation of hexane
To: Discussion list for GROMACS users <gmx-users at gromacs.org>

> Hi all
> 
> I am trying to simulate 150 molecules of hexane in a triclinic box (8.319*3.01*3.01 nm^3) using OPLSAA force field.I got the .gro file from PRODRG and generated the topology using X2top command. when i run energy minimisation for hexane my potential energy is positve. is this right?. what i should correct to get the potential energy as negative. below is my result. any help is highly appreciated.
 > 
> Steepest Descents converged to Fmax < 100 in 10454 steps
> Potential Energy  =  3.4133051e+04
> Maximum force     =  9.8812309e+01 on atom 635
> Norm of force     =  7.9230022e+00

So something is unhappy, and the minimizer can't deal with it. Probably you have some massive steric clash, like two molecules overlying each other. Look at the contents of your simulation cell before and after EM.

Mark
 
> Below is my contents of my em.mdp file
 > 
> integrator        = cg        
> emtol             = 100.0      
> emstep          = 0.01        
> nsteps           = 50000         
> nstcgsteep     = 1000
> nstlist             = 1       
> ns_type          = grid        
>  rlist                = 1.0       
> coulombtype   = PME       
> fourierspacing = 0.12
> rcoulomb        = 1.0       
> rvdw              = 1.0       
> pbc               = xyz 
> 
> Regards
> Vinoth       
> 
 > -- 
> gmx-users mailing list    gmx-users at gromacs.org
> http://lists.gromacs.org/mailman/listinfo/gmx-users
> Please search the archive at 
> http://www.gromacs.org/Support/Mailing_Lists/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/Support/Mailing_Lists
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://maillist.sys.kth.se/pipermail/gromacs.org_gmx-users/attachments/20101006/bec7cb13/attachment.html>