atomic charges from bader

[jiddy]

I ran Bader with the example file for H2O (gaussian cube). The BCF.dat looks like this:
# X Y Z CHARGE ATOM DISTANCE
-------------------------------------------------------------------------
1 0.0000 -1.4362 0.9827 0.3766 3 0.0060
2 0.0000 0.0000 -0.1512 9.2510 2 0.0282
3 0.0000 1.4362 0.9827 0.3766 1 0.0059

I did the chelpg calculation in Gaussian with the same geometry and the partial charges turn out to be:
1 H 0.181065
2 O -0.362130
3 H 0.181065

The 9.25 charge for the oxygen doesn't make sense. Is there any conversion needed from Bader to Chelpg format?

[graeme]

The Bader charges reported by our program are the total number of electrons around that atom. Since O has a valence of 8, the net charge is -1.25. It is +0.52 on the two H atoms. Check with higher grid densities for convergence of these numbers (they should add to zero).

[jiddy]

Is it the total number of electron or the valence electron? In the H2O case, I guess the total electron makes more sense. However, I tried the other example C2H4. The total electron in the ACF.dat is 12.000 which is 4*2+1*4. The valence electron is 4 for C but the total number is 6. It is a little confusing. Could you clarify this?

[graeme]

The Bader program reports the total number of electrons around each atom found in your charge density file. If you did an all-electron calculation, it will report the total number of electrons. If you did a calculation with only the valence electrons, it will report that number. There is no interpretation or analysis of these numbers in the Bader program -- it simply sums the number of electrons in your charge density file around each atom according to the Bader partitioning.