[CP2K:3092] guidelines on implementing special kind of collective variable

Teodoro Laino teodor... at gmail.com
Wed Feb 9 13:35:52 UTC 2011

Dear Peter,

it is by far not an immediate task: you need to run 2 SCF calculations for a same geometry (which is not available at the moment).
In principle, with some modification you may use a fake mixed_env (2 calculations, using only 1 (the neutral I guess) for propagation). 
But you still need to implement the possibility of storing/retrieving the energy/forces of the two systems independently.
Feasible but not immediate: You need to be extremely well acquainted with the code to implement something like that.

Or alternatively one could implement the possibility to run an additional SCF (without messing up the extrapolation guess) during an MD: in your case you would propagate the neutral system and compute for each geometry an energy/forces for the negative one.


On Feb 9, 2011, at 2:20 PM, Peter wrote:

> Dear CP2K developers!
> I would like to try to implement a special type of collective
> variable: it is a difference between potential energy of a system and
> potential energy of the system in the same geometry with an extra
> electron. In other words, I want to use vertical ionization energy as
> a collective variable for e.g. metadynamics.
> If there are any caveats regarding this task? E.g. with potential
> derivatives calculation.
> Could you please give some guidelines on implementing this in cp2k?
> Thanks,
> Peter
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