Self-consistent charge equilibration method and its application to Au13Na(n) (n = 1,10) clusters.

We modified the charge equilibration method (QEq) of Rappe et al. by including the third and fourth order terms in the series expansion for the energy of charged atoms. This leads to a self-consistent scheme for obtaining charges and total energy in a molecule. We combined the modified QEq with a scaled morse potential (SMP) to get a new potential, SMP/QEq. The SMP/QEq method allows to do realistic geometry optimizations and calculate reliable charge distributions and ionization energies. The performance of SMP/QEq was fully tested by comparing to high level theories and experiments. We established a connection between first-principles DFT and SMP/QEq which gives insight into SMP/QEq and suggests ways to improve it.