[CP2K-user] Electronic density cube file not implemented for DFTB method。

[Maxime Van den Bossche]

 Dear Evelyn,

I'm not a CP2K developer, but I suspect that the following is at play here:

In a DFTB implementation, the basis functions themselves do not need to be 
known,
as the required information for e.g. building the Hamiltonian and overlap 
matrices
is provided via the (one- and two-center) integrals in the Slater-Koster 
files.

So, from only those files, the DFTB module in e.g. CP2K would not know how 
to
construct the electron density (or molecular orbitals, for that matter) 
from e.g.
the wavefunction coefficients or the density matrix.

In the DFTB+ code, this can be done (in a post-processing step) by 
describing
the basis functions using Slater-type orbitals, see e.g.

https://dftbplus-recipes.readthedocs.io/en/latest/basics/waveplot.html
https://dftbplus.org/fileadmin/DFTBPLUS/public/dftbplus/latest/manual.pdf#chapter.7

At least, I think this explains why this is not (yet) implemented in CP2K.

If you can get your hands on e.g. the wave function coefficients, and have 
the required
information on the basis functions, you may of course compute the electron 
density
yourself.

Best,
Maxime

Op zaterdag 12 december 2020 om 14:29:13 UTC+1 schreef ea... at gmail.com:

> hello
>
> I'm a beginner, and I want to try running  a monolayer of  HBN  using the DFTB method, and then output the charge of the atom.But there are always mistakes 。I want to know what the problem is.The display error is Electronic density cube file not implemented for DFTB method。
> #CPQA INCLUDE DFTB/nonscc/nonscc_parameter
> #CPQA INCLUDE uff_table
> #CPQA INCLUDE DFTB/nonscc/bn
> #CPQA INCLUDE DFTB/nonscc/nb
> &FORCE_EVAL
>   METHOD Quickstep
>   &DFT
>     &QS
>       METHOD DFTB
>       &DFTB
>         SELF_CONSISTENT    F
>         &PARAMETER
>           PARAM_FILE_PATH  DFTB/nonscc
>           PARAM_FILE_NAME  nonscc_parameter
>         &END PARAMETER
>       &END DFTB
>     &END QS
>     &SCF
>       SCF_GUESS NONE
>       &MIXING
>           METHOD DIRECT_P_MIXING
>           ALPHA   1.
>       &END
>       MAX_SCF 5
>     &END SCF
>    &PRINT
>     
>        &E_DENSITY_CUBE
>          FILENAME cube
>          STRIDE 1 1 1
>        &END E_DENSITY_CUBE
>        
>    &END PRINT
>   &END DFT
>   &SUBSYS
>     &CELL
>       ABC  64 63 2
>       PERIODIC NONE
>     &END CELL
>     &TOPOLOGY
>     COORD_FILE_FORMAT PDB
>     COORD_FILE_NAME HBN1.pdb
>     &END TOPOLOGY
>   &END SUBSYS
> &END FORCE_EVAL
> &GLOBAL
>   PROJECT hbn
>   RUN_TYPE MD
>   PRINT_LEVEL LOW
> &END GLOBAL
> &MOTION
>   &MD
>     ENSEMBLE NVT 
>     STEPS  10
>     TIMESTEP 1
>     TEMPERATURE 300.0
>     &THERMOSTAT
>       &NOSE
>         LENGTH 3
>         YOSHIDA 3
>         TIMECON [wavenumber_t] 2000
>         MTS 2
>       &END NOSE
>     &END
>   &END MD
> &END MOTION
>
> Thank you in advance for your help!  
>
> Best regards，
> Evelyn  
>
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