[CP2K:10094] Jumps in potential energy in ad- buffer force QM/MM simulations

Noam Bernstein no... at bollweevil.gdbg.org
Thu Mar 15 18:09:08 UTC 2018

On Thu, Mar 15, 2018 at 5:26 AM, Rahul Hardikar <hardika... at gmail.com>

> Dear Experts,
> How can one understand the equilibration when using an adaptive buffer
> force QM/MM simulation. The reason is that when I plot the K.E., T and P.E.
> over the trajectory
> there are jumps in P.E. due to change in number of atoms in the QM_CORE
> and QM_BUFFER regions. The K.E. and T however do not show these jumps at
> all.
> What is the best way to scale the P.E. in order to see/show the
> equilibrated region. Please find the plot attached for your reference.

The ad-buf QM/MM does not conserve energy - the only thing it tries to do
is always have reasonable forces.  Since forces are the only thing that
matters to the trajectory, the MD will continue, and nothing in particular
should happen to KE even though PE is discontinuous.  I don't understand
why this has anything to do with equilibration, though.

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