UT theoretical chemistry code forum

Dear all,

I am a beginner of Bader analysis and I have read the instructions at "http://theory.cm.utexas.edu/bader/vasp.php", but I still puzzled by the differences between 'ACF.dat' vs 'BCF.dat' and 'Atomic volume' vs 'Bader volume' ?

Take TiO2 for example,according to a oversimplified ionic model: Ti +4 O -2, valence electrons Ti 4 O 6. Now I want to perform Bader analysis to estimate numerically the amount of electrons redistributed between Ti and O. I use VASP 4.6.31 with PAW-PBE and I have already got the converged AECCAR0, AECCAR1, AECCAR2 and chgsum.pl.

The questions are:
1.What are the differences between 'ACF.dat' vs 'BCF.dat' ? 'Atomic volume' vs 'Bader volume' ?
2. Concerning my example mentioned above, which charg file I should use? so that I can use the charge of Ti in ACF.dat or BCF.dat minus 4, use the charg of O in ACF.dat or BCF.dat minus 6, to get the real velence state :Ti+x O-y?

Thanks a lot!

The Bader analysis integrates charge around each charge density maximum. There is one Bader volume around each charge density maximum. These are listed in the BCF.dat file; this is the raw output of the calculation.

Typically, one is interested in the charge associated with the atoms. When there is a single charge density maximum at each atomic center, the ACF.dat file (atomic volumes) will have the same information as the BCF.dat file (Bader volumes). But in some cases, for example with calculations using pseudopotentials, there can be several charge density maxima around the atomic cores. The ACF.dat file lists each atomic center and the total charge in all of the Bader volumes (listed in BCF.dat) with charge density maxima which are nearest to that atom. The ACF data also avoids the problem of numerous charge density maxima within noise in vacuum regions far from any atom.

If you are including core charge in your calculations, the ACF.dat and BCF.dat files should give the same partial charges. For calculations with fragmented atomic volumes, the ACF.dat file is better, but you need to make sure that the Bader volumes in the BCF.dat file are cleanly associated with nearest atoms. Otherwise, it is up to you what to do with the BCF.dat (Bader volume) data.

[quote="graeme"] you need to make sure that the Bader volumes in the BCF.dat file are cleanly associated with nearest atoms. (Bader volume) data.[/quote]
Thanks, Dr.Graeme, but How can I check whether "the BCF.dat file are cleanly associated with nearest atoms." ?

The charge density maxima should be located near the atomic centers.

Dear Prof. Graeme,

Besides bader charge, what information we can get from bader charge analysis output. Is there any output which we can plot and visualize and by which software ?

How does calculate charge transfer by bader analysis output of two system pure one and doped one. I want to check charge transfer by dopant ?

Thank You
Shilendra