[CP2K-user] Calculating forces from velocities and positions in MD simulation

[Shweta Jindal]

Hi everyone,

I tried to run an MD simulation using velocity verlet integrator. I saved 
the position and velocities for all the structures of the trajectory. 
Unfortunately, I didn't save forces. Is there a way I can obtain the forces 
from positions and velocities information? 

P.S. I tried the velocity verlet equations to calculate acceleration and 
then forces, but couldn't get them right. It will be very helpful if you 
can suggest some way to get the forces.

I assumed the units in MD as follows:

units of position : Angstrom,
units of velocities : bohr/au_t    (au_t = 0.0242fs)
units of forces : Ha/Bohr

Thanks,
Shweta
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