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

Rahul Hardikar hardika... at gmail.com
Fri Mar 16 05:06:36 UTC 2018

Thanks Noam!

On Thursday, March 15, 2018 at 11:39:12 PM UTC+5:30, Noam Bernstein wrote:
> On Thu, Mar 15, 2018 at 5:26 AM, Rahul Hardikar <hardi... at gmail.com 
> <javascript:>> wrote:
>> 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.
>             Noam
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