[CP2K-user] [CP2K:19052] Unit conversion for PW_CUTOFF

[Lucas Lodeiro]

Maybe this information is useful:
https://www.cp2k.org/howto:running_qe_computation

in short terms, the energy (E) of a plane wave with a wave vector G is: E =
(h/2pi)²G²/(2m_e) which is reduced to (if a.u. is used): E = G²/2
so, E in Ha (a.u.) and G in a.u.
The G value is the input for SIRIUS, so you need: G [a.u.] = sqrt(2*E [Ha])
, and in QE the energy is used by default in Rydberg, so E_QE [Ry] = 2E [Ha]
Finally, G [a.u.] = sqrt(E_QE [Ry])

Regards - Lucas Lodeiro


El mar, 4 jul 2023 a las 9:24, Jibiao Li (<science.sweden at gmail.com>)
escribió:

> Hi all,
>
>
>
> According to the manual, units for PW_CUTOFF and GK_CUTOFF are [a.u.^-1].
> I am still puzzled by the question of how I should convert a cutoff energy
> of 80 Ry to that can be accepted by PW_CUTOFF in CP2K.
>
>
>
> I discussed it with Dr. Jürg Hutter, but no definite answer was received.
> Could anyone provide a clear answer?
>
>
> Regards
>
> Jibiao Li
>
> &GLOBAL
>   PROJECT FCC_Copper
>   RUN_TYPE CELL_OPT
>   PRINT_LEVEL LOW
> &END GLOBAL
>
> &FORCE_EVAL
>   METHOD SIRIUS
>   STRESS_TENSOR ANALYTICAL
>   &SUBSYS
>     &CELL
>       A 3.61 0.00 0.00
>       B 0.00 3.61 0.00
>       C 0.00 0.00 3.61
>       SYMMETRY CUBIC
>       PERIODIC XYZ
>     &END CELL
>     &COORD
>       Cu   0.000 0.000 0.000
>       Cu   0.000 1.805 1.805
>       Cu   1.805 0.000 1.805
>       Cu   1.805 1.805 0.000
>     &END COORD
>     &KIND Cu
>        POTENTIAL GTH-PBE-q11
>     &END KIND
>   &END SUBSYS
>   &PW_DFT
>     &CONTROL
>        VERBOSITY 2
>     &END CONTROL
>     &PARAMETERS
>        ELECTRONIC_STRUCTURE_METHOD  pseudopotential
>        GK_CUTOFF ???
>        PW_CUTOFF ???
>        NUM_DFT_ITER 399
>        NGRIDK 10 10 10
>     &END PARAMETERS
>     &ITERATIVE_SOLVER
>        ENERGY_TOLERANCE 1e-5
>        NUM_STEPS 20
>        SUBSPACE_SIZE 4
>     &END ITERATIVE_SOLVER
>     &MIXER
>        BETA 0.3
>        TYPE BROYDEN2
>     &END MIXER
>   &END PW_DFT
>   &DFT
>     &XC
>       &XC_FUNCTIONAL
>         &GGA_X_PBE
>         &END GGA_X_PBE
>         &GGA_C_PBE
>         &END GGA_C_PBE
>       &END XC_FUNCTIONAL
>     &END XC
>   &END DFT
> &END FORCE_EVAL
>
> &MOTION
>   &CELL_OPT
>     MAX_ITER 200
>     OPTIMIZER BFGS
>     KEEP_SYMMETRY .TRUE.
>   &END CELL_OPT
> &END MOTION
>
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