[CP2K-user] [CP2K:12769] Reevaluating energy in geometry optimization

[Patrick Gono]

Dear Khodayar,

The reevaluation of the energy at the end of the optimization might yield a
different total energy value if your calculation is not converged. If that
is the case, you might choose more stringent values for EPS_SCF inside the
SCF subsection, which governs the convergence of the SCF loop, and
EPS_DEFAULT, which is tied to the numerical accuracy of your calculation.
>From the excerpt you provide, I see that the energy changed by 2.71E-05
Hartree, or nearly one meV, in the last iteration before convergence.
That's rather a lot, and hence I'd advise you to decrease EPS_SCF to, say,
1.0E-6.

However, in the end, the two values of total energy differ by less than
0.08 meV. For most intents and purposes, that's identical, and you can
choose whichever.

Yours sincerely,
Patrick Gono

On Sun, 12 Jan 2020 at 08:09, e khodayar <e.khod... at gmail.com> wrote:

> Hi,
> In the main output file geometry optimization,  at the end of  geometry
> optimisation step, I have the following information:
>  --------  Informations at step =    53 ------------
>   Optimization Method        =                   CG
>   Total Energy               =       -94.0112708604
>   Real energy change         =        -0.0000036472
>   Decrease in energy         =                  YES
>   Used time                  =              343.953
>
>   Convergence check :
>   Max. step size             =         0.0006162087
>   Conv. limit for step size  =         0.0010000000
>   Convergence in step size   =                  YES
>   RMS step size              =         0.0002737159
>   Conv. limit for RMS step   =         0.0010000000
>   Convergence in RMS step    =                  YES
>   Max. gradient              =         0.0005305121
>   Conv. limit for gradients  =         0.0010000000
>   Conv. in gradients         =                  YES
>   RMS gradient               =         0.0002356500
>   Conv. limit for RMS grad.  =         0.0010000000
>   Conv. in RMS gradients     =                  YES
>  ---------------------------------------------------
>
>
>  *******************************************************************************
>  ***                    GEOMETRY OPTIMIZATION COMPLETED
>   ***
>
>  *******************************************************************************
>
>                     Reevaluating energy at the minimum
>
>  Number of electrons:
>    68
>  Number of occupied orbitals:
>    34
>  Number of molecular orbitals:
>     34
>
>  Number of orbital functions:
>   232
>  Number of independent orbital functions:
>   232
>
>  Extrapolation method: ASPC
>
>
>  SCF WAVEFUNCTION OPTIMIZATION
>
>   Step     Update method      Time    Convergence         Total energy
> Change
>
> ------------------------------------------------------------------------------
>      1 Pulay/Diag. 0.50E+00    3.7     0.00001087       -94.0112708604
> -9.40E+01
>      2 Pulay/Diag. 0.50E+00    4.7     0.00001294       -94.0112951749
> -2.43E-05
>      3 Pulay/Diag. 0.50E+00    4.3     0.00000783       -94.0112680643
> 2.71E-05
>
>   *** SCF run converged in     3 steps ***
>
>
>   Electronic density on regular grids:        -67.9999999983
> 0.0000000017
>   Core density on regular grids:               68.0000000001
> 0.0000000001
>   Total charge density on r-space grids:        0.0000000017
>   Total charge density g-space grids:           0.0000000017
>
>   Overlap energy of the core charge distribution:
>  0.00000565490189
>   Self energy of the core charge distribution:
>  -223.82607238936723
>   Core Hamiltonian energy:
>  69.37181702794591
>   Hartree energy:
> 89.86177654697752
>   Exchange-correlation energy:
> -29.41879490480421
>
>   Total energy:
>  -94.01126806434611
>
>  ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):
> -94.011268064346112
>
> Now my question is:
> Which total energy i have to use for my data?and why this two total energy
> that with yellow color is different?
> Thanks in advance.
>
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