Charge Transfer and Charge Counts

From FEFF

The charge tranfer in each ‘ldosNN.dat’ file and in ‘log1.dat’ is related to the amount of charge transferred into the Norman radius during the SCF routine. Before the SCF routine, the Norman radius is the radius of the neutral sphere, so the charge transfer can be related to the electronegativity or the oxidation state, although the actual numbers are usually much smaller than the formal oxidation state. The electron counts give the number of valence electrons in each of the angular momentum channels after the SCF has completed. The valence electrons are assumed to be those binding binding energy above and energy ”ecv”, which is usually at -40 eV, but can sometimes change if the atoms in the problem have binding energies close to -40eV. The difference between these numbers and the number of valence electrons in these channels in the atomic system should be equal to the charge transfer into each channel. If these are summed over angular momentum channels, you should get the total charge transfer. The only case where this is different is in the absorbing atom, which starts with and extra electron in the valence. As an example, we can look at NaF which gives

 Electronic configuration
iph  il   N_el
 0   0  0.521
 0   1  6.535
 0   2  0.358
 0   3  0.000
 1   0  1.958
 1   1  5.285
 1   2  0.014
 1   3  0.000
 2   0  0.221
 2   1  6.292
 2   2  0.236
 2   3  0.000

Here iph = 0 is the absorbing Na atom, iph = 1 is the F atom, and iph = 2 is the other Na atom. These atoms start with the configuration

Electronic configuration
  iph    il      N_el
    0     0    2.0  - extra screening electron
    0     1    6.0
    0     2    0.0
    0     3    0.0
    1     0    2.0
    1     1    5.0
    1     2    0.0
    1     3    0.0
    2     0    1.0
    2     1    6.0
    2     2    0.0
    2     3    0.0 

Looking at the difference between these two, you can see that in the solid state, some electrons are transferred from the sodium s to the sodium p and d states, and some to the F p states. There is also a small tranfer from the F s states, and into the F d states, but minor. Note that the final configuration allows more than 6 electrons in the Na p states. This is because the p-states are not limited to the 2p states, but include the 3p as well.

developer's resources