[CP2K-user] Large energy difference between md step and single point calculation

[Marcella Iannuzzi]

Dear Massimo

In the MD the reference cell is used, which is quite different from the 
cell of the single point calculation.
Kind regards
Marcella


On Tuesday, September 22, 2020 at 10:55:14 AM UTC+2 mas... at gmail.com 
wrote:

> Dear CP2K users/developers,
>
> I am extracting some snapshots from an umbrella sampling simulation (with 
> PLUMED as dependency of CP2K 5.1) and I would like to recalculate their 
> energy at a higher level of theory. So to start I performed a single point 
> calculation at the same level of theory of the US simulation (PBE-D3) and, 
> surprisingly for me, I got very different results in the energy. In 
> particular, the energy of the MD step is:
> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):            
> -3520.987951048081868
> While for the single point calculation:
> ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):            
> -3520.903314334958850
> Which is an enormous difference. Attached the two input scripts, the main 
> differences being the RUN_TIPE, the cell parameters (for the single point 
> they are just taken from the md output at the selected step) and the lack 
> of the MOTION section.
> Does anybody have an idea on where this large energy difference could come 
> from?
>
> Thank you in advance, 
> Massimo Bocus
>
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