[CP2K-user] [CP2K:13035] Pseudopotential Energy

[hut... at chem.uzh.ch]

Hi

without more information it is difficult to give correct advice.

Assuming you are calculating a periodic system, the problem is related
to the change in total net charge of the unit cell (+1). Now this is
a well known problem for the calculation of defect energies in solid state
calculations. See for example the recent literature by A.Pasquarello (EPFL).
Similar problems arise in the calculation of pKa's, see the many papers by
M. Sprik (Cambridge).
However, if the problem magically is absent in VASP it cannot be the problem
above, but then I cannot see what you are doing.

regards

Juerg
--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp... at googlegroups.com wrote: -----
To: "cp2k" <cp... at googlegroups.com>
From: "Nicholas Winner" 
Sent by: cp... at googlegroups.com
Date: 03/29/2020 05:50AM
Subject: Re: [CP2K:13035] Pseudopotential Energy

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            
             

Thank you in advance.

-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 
Winterthurerstrasse 190 
CH-8057 Zürich, Switzerland 
--------------------------------------------------------------- 
 
-----c... at googlegroups.com wrote: ----- 
To: "cp2k" <c... at googlegroups.com> 
From: "Nicholas Winner"  
Sent by: c... at googlegroups.com 
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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