Vasp Spin Polarized calculation

[gVallverdu]

Hello

I would like to know if bader is able to deal with spin polarized CHGCAR output. As in non spin polarized calculation I can produce AECCAR* files and I would like to use them to compute bader charges. I would like to know what do your code do ? Does it simpy add alpha and beta density ? What about chgsum.pl ?

I have one more question about AECCAR* files. In vasp release note you can find :
+ 08.02.2006: AE core charges added
the flag LAECHG = .TRUE. allows to get the total chargedensity
(including core charge density on a regular grid)
we recommend to use a rather fine FFT grid in this case and to set LADDGRID=.TRUE.
three files are written
AECCAR0 core charge density
AECCAR1 atomic AE charge density (overlapping atomic charge density)
AECCAR2 AE charge denisty

The tag LADDGRID is never referenced in the VASP manuel can you said something more about it ? Here Vasp developpers said that AECCAR2 is the All electron charge density ? Is it true or is it only the valence charge density ? If it's that, then are these sentences true ? :

AECCAR0 + AECCAR1 is the initial total charge density (the guess when istart=0).
AECCAR0 + AECCAR2 is the converged total charge density at then end of the calculation.

Thanks

[graeme]

Yes, we can analyze spin polarized CHGCAR files. By default it will read the first (up+down) data set and work as you would expect for the total charge density. If you want to analyze the second (up-down) spin polarization data, you can use our chgsplit script and run (for example) "bader CHGCAR_mag -ref CHGCAR_sum" where CHGCAR_sum is obtained by summing the AECCAR0 and AECCAR2 (see: http://theory.cm.utexas.edu/bader/vasp.php )

The LADDGRID tag is the same as ADDGRID; see: http://cms.mpi.univie.ac.at/vasp/guide/node142.html

[gVallverdu]

Thanks,

Just one more question.

In the web page of the bader program you do not explain what is the meaning of the -ref tag. I understand that the bader analyses needs to identify density maxima so you need the core density. Can you explain what do you do with the files CHGCAR and CHGCAR_sum and the meaning of -ref ?

[graeme]

Using "-ref CHGCAR_sum" specifies that the bader partitioning be done on the total charge density. This is not, however, nessecarily the charge density that you want to integrate within the Bader volumes. In the example I gave "bader CHGCAR_mag -ref CHGCAR_sum" it would be the spin density (CHGCAR_mag) which is integrated in the Bader volumes. Typically we use this flag so that the partitioning is done with the total (core + valence) charge and the integration is done using just the valence electrons.