[gmx-users] LR electrostatics in single point energy calculations

rajat desikan rajatdesikan at gmail.com
Wed Jan 15 17:38:44 CET 2014

Hi Justin,

I used the following commands:

mdrun_mpi -s md_6_50ns.tpr -rerun md_6_50ns.gro
gmxdump_mpi -e ener.edr > ener_readme

And in the dump of the ener_readme file, I have the following terms:

Coul-SR:Protein-Protein  -6.62324e+05
LJ-SR:Protein-Protein  -5.64854e+04
Coul-14:Protein-Protein   4.04345e+05
LJ-14:Protein-Protein   3.29438e+04

Coul-SR:Protein-POPC  -1.97403e+03
LJ-SR:Protein-POPC  -4.64531e+03
Coul-14:Protein-POPC   0.00000e+00
LJ-14:Protein-POPC   0.00000e+00


There is neither a Coul-recip nor a Coul-LR term. So, I was wondering about
it. The Coul-recip is the reciprocal space term in a Ewald summation
calculation, right? I want the total potential energy of the protein. How
would I go about that?


On Wed, Jan 15, 2014 at 7:39 PM, Justin Lemkul <jalemkul at vt.edu> wrote:

> On 1/15/14, 7:14 AM, rajat desikan wrote:
>> Hi All,
>> I was wondering about the long range electrostatics while calculating
>> single point energies. I did a cursory calculation for a protein in water
>> (PME) and found that the LR electrostatic terms were zero. I know that the
>> per-particle decomposition of the LR electrostatics is non trivial. I was
>> wondering if there is a way to do it in Gromacs?
> Was the Coul-recip term actually zero, or were you looking at Coul-LR?
>  The two terms mean very different things.
> -Justin
> --
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> Justin A. Lemkul, Ph.D.
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Rajat Desikan (Ph.D Scholar)
Prof. K. Ganapathy Ayappa's Lab (no 13),
Dept. of Chemical Engineering,
Indian Institute of Science, Bangalore

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