On Friday 02 January 2009 09:15:05 am Bruce Ravel wrote:
what does charge transfer mean in FEFF? I cant understand what the number of charge transfer like 0.058, -0.073 means. The number indicate the number of electron in atom? If anybody knows it, please answer
Charge transfer: iph charge(iph) 0 0.058 1 -0.073 2 0.072
Jeong, Feff8 does a trick called "self-consistent potentials". It works like this: Feff8 sarts by computing the muffin tin potentials in a many rather similar to Feff6. It then computes the electronic densities of states for a reasonable set of low-value angular momentum states (usually up to l=3). With those DOS calculation, it integrates in energy to find the energy at which the integral of the DOS equals the number of valence electrons in the system. It is likely that each atom has a different number of electrons than the free atom. Now each atom is differently charged than the starting configuration. The muffin tin potentials are recomputed, the DOS is recomputed, and the integral is done again. This process is repeated until the charge on each atom stops changing. That is the sense in which it is self-consistent. At the end of this self-consistency loop, Feff8 reports the net change in charge (in units of number of electrons) on each atom type. In your case, to attain self-consisteny, a small bit of charge is added to the absorber and a small bit of charge is taken away from the other two atoms. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/