Densities, Self Consistency, Bond Orders

EX. CHARGE DENSITIES, SELF CONSISTENCY, BOND ORDERS... 

We have the makings of an iterative computer method. Start by assuming values for the matr ix elements and calculate electron densities (charge densities and bond orders). Modify the matr ix elements according to the results of the electron density calculations, rediagonalize using the new matrix elements to get new densities, and so on. When the results of one iteration are not different from those of the last by more than some specified small amount, the results are self-consistent. 

Density Functional Theory, DFT (B3LYP), CASSCF (Complete Active-State Self-Consistent Field) and MRSD-CI (Multi-Reference Single-Double Correlation Interaction) calculations on the diatomic units AuO, AuO", AuO " and AuO " clearly show that stability of Au-0 bond reduces in this order. This trend is consistent with the molecular orbital diagram of AuO molecule presented in Fig. 10. 

The initial Hiickel calculations can be employed to obtain preliminary values for the electron densities and bond orders, from which the self-consistent field matrix elements can be evaluated by introduction of the chosen core potentials and electron repulsion integrals.11 Table I lists the ionization potentials, electron affinities and nuclear charges employed in the present calculations. 

In order to show the effect that inclusion of the correlation energy in a self-consistent way has on the electron density, as in ref. , we show in figures 4-7 the difference between the SCF and post-SCF densities (the post-SCF density is just the GVB-pp density). Figures 4,5 show the full electronic density difference for LiH and Li2, and figures 6,7 the valence bond-pair electron density difference for LiH and FH. 

---