[gmx-developers] Wall interaction with tabulated potential

[Sudharsan Pandiyan]

Hi,

I generated the tables using the csg_call routine from the VOTCA-CSG program and I input 1.0 for sigma and epsilon values in topol.top file (1 also for the combination rule). I also generated the LJ particle interaction table for interaction between the particles in the simulation box, which gives exactly same potential energy for both table potential and 12-6 potential. But the wall-particle interaction produces different values.

Sincerely,

Sudharsan

________________________________
From: gromacs.org_gmx-developers-bounces at maillist.sys.kth.se [gromacs.org_gmx-developers-bounces at maillist.sys.kth.se] on behalf of Sudharsan Pandiyan [sudharsan.pandiyan at chem.kuleuven.be]
Sent: 05 February 2016 11:08
To: gmx-developers at gromacs.org
Subject: Re: [gmx-developers] Wall interaction with tabulated potential

Hi Berk,

Thank you very much for quick reply. But, I input 1.0 for sigma and epsilon values. Still the problem persists.

Sincerely,

Sudharsan
________________________________
From: gromacs.org_gmx-developers-bounces at maillist.sys.kth.se [gromacs.org_gmx-developers-bounces at maillist.sys.kth.se] on behalf of Berk Hess [hess at kth.se]
Sent: 05 February 2016 10:42
To: gmx-developers at gromacs.org
Subject: Re: [gmx-developers] Wall interaction with tabulated potential

Hi,

You should not put sigma and epsilon in the table. The dispersion and repulsion table get multiplied by C6 and C12, respectively.

Cheers,

Berk

On 2016-02-05 09:57, Sudharsan Pandiyan wrote:
Dear Gmx developers,

I am trying to simulate a wall option using tabulated potentials option. But it gives different LJ potential values when I compare 12-6 potential with the tabulated potential (where the table was generated using same sigma and epsilon values that were used for 12-6 potential).

I intend to modify my table potential later so I wanted to make sure that it produces correct result. But my test shows that there is a difference between 12-6 and tabulated potentials for wall interaction. Could you please explain what is the difference and how can I get the correct potential energy for tabulated potentials?

PS: In the manual, its written that both 9-3 and 10-4 are integrated over the surface area and 12-6 potential was applied directly with the z-distance. But how the tabulated potential is represented? (section 7.3.20)


Thank you very much for your time and support.

Sincerely,

Sudharsan




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