DDEC6 Charges - Trebonius91/utils4VASP GitHub Wiki

Another possibility to calculate atomic partial charges with VASP is the density derived electrostatic and chemical (DDEC) method by Manz et al. (paper 1, paper 2).

It partitions the electron and spin densities to calculate net atomic charges and other properties like spin moments and bond orders.

The analysis can be done with the Chargemol program. It needs to be downloaded from the Sourceforce website. There, choose the chargemol_09_26_2017.zip option. After downloading, unpack the archive and find the precompiled binaries in the chargemol_FORTRAN_09_26_2017/compiled_binaries/linux subfoder. Usually, these should work directly; if not (or you are on Windows), compile the Fortran source code.

The procedure for obtaining DDEC6 charges is similar to that for Bader charges. Perform a usual single point calculation, with the same settings as for a DOS calculation. The NEDOS and EMIN as well as EMAX keywords can of course be ignored. To the INCAR file, simply add the command:

  • LCHARG = .TRUE.
  • LAECHG = .TRUE.

After running the VASP calculation, four files need to be present for the subsequent analysis:

  • POTCAR
  • CHGCAR
  • AECCAR0
  • AECCAR2

In addition, a main input file for the Chargemol program must be generated, with the name job_control.txt. Its default content is the following:

<net charge>
0.0
</net charge>

<periodicity along A, B, and C vectors>
.true.
.true.
.true.
</periodicity along A, B, and C vectors>

<atomic densities directory complete path>
[absolute path]/chargemol_09_26_2017/atomic_densities/
</atomic densities directory complete path>

<charge type>
DDEC6
</charge type>

<compute BOs>
.false.
</compute BOs>

Most important is the <atomic densities directory complete path> section. Here, the absolute path to the atomic_densities subfolder in the Chargemol directory must be copied (with a final / sign!). Further, the total charge of the system is set in the <net charge> section. Bond orders can be calculated as well. They are deactivated here because we are only interested in the calculation of partial charges.

To execute the program, simply type:

 Chargemol_09_26_2017_linux_seria

or

 Chargemol_09_26_2017_linux_parallel

where the last has OMP parallelization.

During execution, the output is written to the log-file VASP_DDEC_analysis.output. After finalizing, the DDEC6 charges of the atoms are written to the file DDEC6_even_tempered_net_atomic_charges.xyz.

These results can be further evaluated and visualized with the analyze_dft program (-ddec6 command).

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