[gmx-users] rlist and rlistlong in gmx451

[Justin A. Lemkul]

Carlo Camilloni wrote:
> Dear Gromacs Users and Developers,
> 
> I am testing gromacs-4.5.1 with different running parameters, in particular
> switching potentials and rlistlong.  I have a question about this NOTEs given
> by grompp when rlist=rvdw=rcoulomb (I thought that was rlonglist that should be
> longer than rvdw and rcoulomb):
> 
> NOTE 1 [file qua.mdp]:
>  For energy conservation with switch/shift potentials, rlist should be 0.1
>  to 0.3 nm larger than rcoulomb.
> 
> 
> NOTE 2 [file qua.mdp]:
>  For energy conservation with switch/shift potentials, rlist should be 0.1
>  to 0.3 nm larger than rvdw.
> 
> I am using:
> rlist                    = 1.2
> rlistlong                = 1.5
> coulombtype              = pme-switch
> rcoulomb-switch          = 1.0
> rcoulomb                 = 1.2
> vdw-type                 = switch
> rvdw-switch              = 1.0
> rvdw                     = 1.2
> 
> 
> If rlist should be larger than rvdw what's the use of rlonglist?
> 

The value of rlistlong is only relevant when using twin-range cutoffs (per the 
manual), which you are not (rlist=rcoulomb=rvdw).  Note that this equality leads 
to bad energy conservation, as grompp is warning you.  Increase rlist properly 
and you should have no problem.

-Justin

> Thanks,
> Carlo
> 

-- 
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Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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