[gmx-users] adding an external body force

[Justin Lemkul]

On 2/6/20 4:58 AM, Michele Pellegrino wrote:
> Hi,
>
>
> I was wondering how to apply an external forcing term to one group; looking at the 2020 documentation I found:
>
>
> "
>
> accelerate group
> On each atom in an "accelerate group" an acceleration a_g is imposed. This is equivalent to an external force.
>
> "
>
>
> However I would argue it is not equivalent at all: the contibution of an external body force would add an acceleration term, not impose it, right?
>
> To make a more concrete example, what if I want to simulate gravity by setting 'accelerate' to some value? Would I obtain free-falling or would gravity be added on top of the force field from atomic intercations?

The use of acceleration groups simply adds an acceleration to the one 
that arises from the forces in the simulation and acts in the update step.

-Justin

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Justin A. Lemkul, Ph.D.
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