[CP2K-user] [CP2K:20895] Re: Free energy from CP2K calculations

[Patrick J. Taylor]

Hi Ashley,

Yes, the "Total energy:" includes the electronic entropy and can therefore 
be considered a free energy in the sense that you are looking for (see also 
towards the end of this tutorial 
<https://www.cp2k.org/howto:static_calculation>).

For reference, you should also see a line beginning "ENERGY| Total 
FORCE_EVAL (QS) ..." elsewhere in your output file, which is the energy 
extrapolated to sigma = 0 (i.e. the "total energy" that one is usually 
interested in).

Thanks,

Patrick
On Thursday, November 7, 2024 at 11:25:14 AM UTC Ashley Dickson wrote:

> Hi all, 
>
> I'm currently working on fitting a machine learned potential using DFT 
> data from CP2K, however I am running into some confusion regarding the 
> energies of the simulations. I am using GAP_fit (
> https://libatoms.github.io/GAP/gap_fit.html), which mentions the 
> importance of fitting the potential to the free energy, in order that the 
> forces are consistent. Am I understanding correctly that the Total energy 
> printed by CP2K is equivalent to the free energy, and includes the 
> electronic entropic energy? 
>
> For instance, the isolated atom energies are required by GAP_fit to fit 
> the binding energies of the potential, so I have performed a SPE 
> calculation on oxygen to give the following output:
>
> Overlap energy of the core charge distribution:               
> 0.00000000000000
>   Self energy of the core charge distribution:               
>  -41.52620707899887
>   Core Hamiltonian energy:                                     
> 11.40342642720691
>   Hartree energy:                                             
>  17.59013700141358
>   Exchange-correlation energy:                                 
> -3.24820705673776
>   Electronic entropic energy:                                 
>  -0.02418867401250
>   Fermi energy:                                               
>  -0.32715630556588
>
>   Total energy:                                               
> -15.80503938112864
>
>
> Would I take -15.80503938112864 as the isolated atom energy here?
>
> Thanks in advance,
> Ashley
>

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