[gmx-users] Re: long range energy
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Mon Jan 22 14:59:02 CET 2007
>From: "Richard Vadnais" <Richard.Vadnais at usherbrooke.ca>
>Reply-To: Discussion list for GROMACS users <gmx-users at gromacs.org>
>To: <gmx-users at gromacs.org>
>Subject: [gmx-users] Re: long range energy
>Date: Mon, 22 Jan 2007 08:46:52 -0500
>>Richard Vadnais wrote:
>>> I want to find four types of energies from my simulation: LJ and
>>>Coulomb at long and short range. I use PME for coulomb type and cut-off
>>>for VdW type with rlist = rcoulomb = 0.9
>>> However, the LJ (LR) and Coulomb LR are not generated in the output
>>>nor can I get them with g_energy.
>>That's because they aren't defined when rlist = rcoulomb. Have a read of
>>the relevant manual sections.
> I read these sections and this is where I am confused. It is specified
>that PME cannot be used with rlilst different than rcoulomb but that if
>they are egal, long range energies would not be defined. However, I am
>trying to reproduce a simulation done by a former member of our research
>group and from the input files (.mdp) he used, I found that he used:
>rlist = 1.05
>coulombtype = PME
> From what I gathered from the manual, this combinaison is not possible,
>however, not only did he get results from this input, but he had the four
>types of energies: LJ-(SR), LJ-(LR), coulomb-(SR), coulomb-(LR).
> (I should have been more precise in my first post. I apologies.)
You must be using an older version of Gromacs then.
In 3.3.1 I have added a check on this in grompp.
So now you have the PP (particle-particle) part of PME below
rlist in Coulomb-SR, the PP part of PME above rlist (updated only
every nstlist steps) in Coulomb-LR and, if your version is not too old,
the reciprocal space contribution in Coul.-recip.
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