[gmx-users] How to modify code so that rlist > rcoulomb

[Jeetain Mittal]

Hi Berk,

Thanks for your response. I am trying to simulate the following options,

ns_type         = grid
rlist                = 3.2
coulombtype = pme
rcoulomb       = 1.0
vdw-type        = cut-off
rvdw               = 3.0
fourierspacing  = 0.12
pme_order       = 4
ewald_rtol      = 1e-5
optimize_fft    = yes

I tried the following with gromacs 3.3.99_development_200800503,

ns_type         = grid
rlist                = 3.2
coulombtype = pme-switch
rcoulomb       = 1.0
rcoulomb_switch = 0.0
vdw-type        = shift
rvdw               = 3.0
rvdw_switch   = 0.0
fourierspacing  = 0.12
pme_order       = 4
ewald_rtol      = 1e-5
optimize_fft    = yes

and it works. I want something similar to PME-Switch (rlist >  
rcoulomb) but without shifting the real space coulomb part.  Is this  
possible? When I try the option rcoulomb_switch > rcoulomb, it gives  
an error.

Thanks,
Jeetain

 > Hi,

 > You did not specify for which type of vdw and electrostatics you  
want this option.
 > For plain cut-off's it does not make sense.
 > In version 3.3 you can do what you want with the shift and switch  
options.
 >
 > In the CVS version there are also Reaction-Field-zero and PME-Switch.
 >
 > Berk.


 > From: jeetain at gmail.com
 > To: gmx-users at gromacs.org
 > Date: Sat, 19 Jul 2008 16:38:59 -0400
 > Subject: [gmx-users] How to modify code so that rlist > rcoulomb
 >
 > Hi All,
 >
 > I want to simulate a system for which rvdw > rcoulomb and to account
 > for LJ interactions correctly rlist should be greater than rvdw (if
 > nstist != 1). For current gromacs setup rlist should be equal to
 > rcoulomb. I searched the mailing list and there has been several
 > discussions related to this issue such as,
 >
 > http://www.gromacs.org/pipermail/gmx-users/2006-July/022804.html
 >
 > I was wondering if anyone has implemented something already so that a
 > system with,  rlist > rvdw > rcoulomb, can be simulated without any
 > problem. Can anyone please guide me what files / variables should be
 > changed to implement this.
 >
 > Thanks,
 > Jeetain
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