[gmx-users] VDW Cut-off vs Switch with CHARMM force field

[James Krieger]

Here is a relevant previous discussion 
http://lists.gromacs.org/pipermail/gmx-users/2013-May/081425.html

Best wishes
James

On 25 Aug 2013, at 00:28, James Krieger <jkrieger at mrc-lmb.cam.ac.uk> wrote:

> CHARMM is generally used with vdw switching between 1.0 and 1.2 nm - I presume it must be more accurate that way. There are a number of discussions on this already. Justin recommended using rlistlong 1.4 as well I think. You might want to use a short range cutoff (rcoulomb) of 1.2 for PME as well. That is what was done in the Bjelkmar et al paper where CHARMM27 was implemented in GROMACS (http://pubs.acs.org/doi/full/10.1021/ct900549r).
> 
> Best wishes
> James
> 
> On 24 Aug 2013, at 23:08, Gianluca Interlandi <gianluca at u.washington.edu> wrote:
> 
>> Hi!
>> 
>> I am running explicit solvent simulations with the CHARMM force field implemented in gromacs 4.6.3. For VDW I have been using:
>> 
>> rlist    = 1.0
>> vdw-type = Cut-off
>> rvdw     = 1.0
>> 
>> in conjunction with PME and rcoulomb=1 for electrostatics.
>> 
>> I wonder whether it would be more accurate to use instead a switching function for VDW between 0.8 and 1.0 and a larger rlist:
>> 
>> rlist       = 1.2
>> vdw-type    = Switch
>> rvdw_switch = 0.8
>> rvdw        = 1.0
>> 
>> My question is: does switching between 0.8 and 1.0 generate less artifacts than abrupt truncation at 1.0 nm for VDW?
>> 
>> Thanks!
>> 
>>    Gianluca
>> 
>> -----------------------------------------------------
>> Gianluca Interlandi, PhD gianluca at u.washington.edu
>>                   http://artemide.bioeng.washington.edu/
>> 
>> Research Scientist at the Department of Bioengineering
>> at the University of Washington, Seattle WA U.S.A.
>> -----------------------------------------------------
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