[gmx-users] Re: Tabulated potentials and normal nonbonded interaction at the same time

[Mark Abraham]

----- Original Message -----
From: Thomas Schlesier <schlesi at uni-mainz.de>
Date: Thursday, September 16, 2010 19:49
Subject: [gmx-users] Re: Tabulated potentials and normal nonbonded interaction at the same time
To: gmx-users at gromacs.org

> Hi,
> first, thank you for you're answers.
> I looked more into the stuff.
> 
> I think i would use the following setup:
> 
> Since the CG-solvent is uncharged, i can use the normal coulomb-
> interaction (PME) for the system.
> 
> For the vdw-part, i would use 'vdw_type=user' and:
> energy_grps = CG Mol
> energygrp_tables = CG CG (CG self-interaction) CG Mol (CG-
> Molecule interaction)
> (CG = CG-solvent; Mol=Molecule)
> So i would need two tables (for each interaction one).
> With this i should get all the vdw-interaction where the CG-
> solvent is involved.
> 
> But since i need normal vdw-interactions for the Molecule self-
> interaction, i would need in the .mdp-file
> 'vdw_type = user' AND 'vdw_type = cut-off'
> 
> Or am i wrong (hope so)? Because the only way i can think of to 
> solve the problem, would be that i make for every vdw-self-
> interaction of the Molecule an own table, which wouldn't be good 
> (since i read somewhere that tables are slower then to 
> calculated the interaction normally).
> 
> So how could i solve the problem, or this there no problem 
> because i didn't understand the whole stuff correctly (seems so 
> because of Marks reply)?

I haven't ever actually done it, but I'm expecting "vdw_type= cut-off" and "energygrp_tables = CG CG CG Mol" to work if you supply the two tables. What I can see in the manual neither confirms nor denies this, but it is cost-free to try :-)

Mark

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