Re: difference between constraining,restraining and fixing the atoms

From: Brian Radak (
Date: Fri Aug 04 2017 - 09:34:22 CDT

Hopefully this clarifies: the "constraint" keyword in NAMD is a horrible
misnomer that is carried over from CHARMM and XPLOR. The keyword
actually applies /restraints./

I'm sure there were notionally good reasons for retaining this
nomenclature when the program was written. Perhaps it is finally time to
alias "restraints" to also activate constraints and slowly deprecate the
legacy syntax?

On 08/03/2017 11:33 PM, Fotis Baltoumas wrote:
> Hello,
> When using fixedAtoms, the atoms defined as fixed never move at all.
> When using constraints, the constrained atoms DO actually move, but
> their movements are constrained with a force defined by the user.
> The choice of using one or the other purely depends on the situation.
> Fotis
> On 04-Aug-17 09:25, wrote:
>> I want to know, what is basically the differnce between
>> constraint/restraint and fixed atom command, and how one can decide
>> which
>> command to be used in a particular situation?
> ---
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Brian Radak
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory
9700 South Cass Avenue, Bldg. 240
Argonne, IL 60439-4854
(630) 252-8643

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