[gmx-users] Group-based cutoff on non-bonded interactions with CHARMM22

[Justin Lemkul]

On 5/20/17 8:28 AM, Dawid das wrote:
> Hi Mark,
>
> Thank you. Actually I want to do some QM/MM calculations with CHARMM22 for
> MM part
> but not using GROMACS and not all things that are implemented in GROMACS
> are available in my
> QM/MM package. Nevertheless, I still want to gather as much data as
> possible.
>

CHARMM force fields do not use multi-atom charge groups.  Each atom is its own 
group, so the neighbor searching is really always atom-based.  So while the 
group and Verlet cutoff schemes are obviously not the same algorithms, with 
respect to the removal of charge groups, they are the same.

-Justin

> Best wishes,
> Dawid
>
> 2017-05-19 22:28 GMT+02:00 Mark Abraham <mark.j.abraham at gmail.com>:
>
>> Hi,
>>
>> Historically that was how things were done. Nobody thinks it is a good idea
>> any more. Use the Verlet scheme plus the recommendations for CHARMM
>> forcefields in GROMACS and you'll be fine - charge groups are removed
>> perforce.
>>
>> Mark
>>
>> On Fri, 19 May 2017 18:44 Dawid das <addiw7 at googlemail.com> wrote:
>>
>>> Dear  Gromacs Users,
>>>
>>> I am a bit confused whether I shouldn't use charge
>>> group-based cut-off for electrostatics when using CHARMM22.
>>> If I shouldn't use it, what is the purpose of specification of charge
>>> groups in
>>> original CHARMM files?
>>>
>>> Best wishes,
>>> Dawid
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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

==================================================