[gmx-users] value for epsilon_rf in a vacuum simulation

[Justin Lemkul]

On 4/30/15 12:34 PM, Rebeca García Fandiño wrote:
> Dear GROMACS users,
> I am trying to carry out a simulation in vacuum (or gas phase). I have doubts about the proper values for epsilon_rf. I have found examples where this value is set to 78
>
>
>                  http://www.shourjya.thinkbiosolution.com/md-simulation-in-gas-phasevacuum-with-gromacs/
>
> and other examples where this value is set to cero (the default value, which means infinite).
>
>
>                  https://extras.csc.fi/chem/courses/gmx2004/exercises/
>
> Which would be the correct value for epsilon_rf in a vacuum or gas phase simulation? What about epsilon_rf=1? Would it not be the best option?
>

It's totally irrelevant.  For gas phase, set all cutoffs to zero, coulombtype = 
cutoff, and no PBC.  This is exactly what is done in the first link, and in that 
case epsilon_rf is ignored (it is only for doing reaction-field electrostatics).

-Justin

-- 
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Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

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