[CP2K-user] [CP2K:18827] Re: Ehrenfest dynamics: Glycine

Matt Watkins mattwatkinsuk at gmail.com
Mon May 22 13:56:19 UTC 2023

Hi Victor,
from your setup the main things are:

   - the cutoff is too small - should be set like a standard DFT 
   calculation - something around 400 Ry and the REL_CUTOFF to 60 Ry or 
   - the timestep is very aggressive. If you plot your energy as function 
   of time I think you will see the conserved quantity drift badly at some 
   point in your simulation and then it explodes. Try something like 
   - stepsize [au_t] 0.1

On Friday, 19 May 2023 at 07:48:32 UTC+1 Victor Volkov wrote:

> Good day.
> I am exploring molecular dynamics under field.
> I set glycine at the center of a box,
> and suggested Ehrenfest dynamics with a time step of about 0.04 fs,
> while the custom field file sets the external field to ZERO. 
> The simulation proceeds alright, till the time-frame 500, after which
> there is a peculiar structural "expansion".
> *Q1: Would you comment this?*
> Also, I attach a fragment of the momentum file:
> CP2K prints reference point position to be "chaotic",
> while I select REFERENCE COAC: since the atomic charges of the glycine, 
> the reference point should be next to the C-alpha atom. 
> *Q2:  would you comment on the usage of the setting I selected?  *
> Thank you.
> Victor

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