# [CP2K-user] [CP2K:13013] Pseudopotential Energy

Nicholas Winner nwi... at berkeley.edu
Sun Mar 29 03:50:42 UTC 2020

```Thank you for your reply Jurg. If you could help clear up one more thing,
it would be greatly appreciated:

The reason I ask is because I have normally used VASP, but am now moving to
CP2K. In VASP, if I wanted to calculate the energy change from inserting,
say, an extra proton, I would run two MD simulations for the system with
and without the proton and take the difference in average total energy.
However, if I do this with CP2K, I get huge differences in energy (100s of
eV), and I would assume this is because VASP subtracts the pseudopotential
energy (in POTCAR, this is EATOM) from the final energy, so it simplifies
the process. So, based on your response, to get a comparable energy
difference, the pseudopotential energies need to be subtracted away.

Assuming the above reasoning is correct, is the energy that I would need to
subtract away the "Total Pseudopotential Energy" reported in the output
file? Or is it "Total Energy"? (Output snipped copied below to make sure
we're on the same page).

*******************************************************************************
>                   Iteration          Convergence
> Energy [au]
>
>  *******************************************************************************
>                           1         1.95724
> -22.935453470232
>                           2         3.60956
> -22.583740788889
>                           3        0.253659
> -23.931824925834
>                           4        0.902351E-02
> -23.939137392463
>                           5        0.379871E-02
> -23.939145271550
>                           6        0.239125E-02
> -23.939146295400
>                           7        0.381467E-04
> -23.939146966990
>                           8        0.294202E-04
> -23.939146967060
>                           9        0.244973E-06
> -23.939146967163
>  Energy components [Hartree]           Total Energy ::
> -23.939146967163
>                                         Band Energy ::
> -4.144745339043
>                                      Kinetic Energy ::
> 18.766431444860
>                                    Potential Energy ::
> -42.705578412022
>                                       Virial (-V/T) ::
> 2.275636608777
>                                         Core Energy ::
> -40.734809390282
>                                           XC Energy ::
> -4.364157452591
>                                      Coulomb Energy ::
> 21.159819875711
>                        Total Pseudopotential Energy ::
> -59.535272206307
>                        Local Pseudopotential Energy ::
> -61.232887828991
>                     Nonlocal Pseudopotential Energy ::
> 1.697615622685
>                                         Confinement ::
> 0.340313711650

-Nick

On Wednesday, March 25, 2020 at 3:00:38 AM UTC-7, jgh wrote:
>
> Hi
>
> CP2K energies include all terms depending on the valence density,
> no constant atomic energy is added/subtracted.
>
> See the base publications for a detailed definition.
>
> This means that total energies depend strongly on the pseudo potentials
> used.
>
> regards
>
> Juerg Hutter
> --------------------------------------------------------------
> Juerg Hutter                         Phone : ++41 44 635 4491
> Institut für Chemie C                FAX   : ++41 44 635 6838
> Universität Zürich                   E-mail: h... at chem.uzh.ch
> <javascript:>
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----c... at googlegroups.com <javascript:> wrote: -----
> To: "cp2k" <c... at googlegroups.com <javascript:>>
> From: "Nicholas Winner"
> Sent by: c... at googlegroups.com <javascript:>
> Date: 03/24/2020 08:35PM
> Subject: [CP2K:13013] Pseudopotential Energy
>
> Does CP2K subtract away the pseudopotential energy when calculating total
> energy in an SCF cycle?
>
> So the actual total energy would then be the reported total energy minus
> the sum of the pseudopotential energies?
>
> I think I read somewhere on this forum that it does not, but cannot seem
> to find it.
>
> Thanks for the help,
> Nick Winner
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