Optimized double configuration

Fig. 11. Calculations on Fj (89) Hartrcc-Fock (HF), optimized double configuration (ODC) and...

Neglect of Diatomic Differential Overlap Natural Spin Orbital Optimized Double Configuration Optimized Valence Configuration Potential Energy... 

The simplest type of MC-SCF wavefunction is one composed of just two configurations. It is often possible to choose the two configurations in such a way as to ensure that the dissociation products are correctly described. Das and Wahl first introduced this method119 arguing that it corrected the most important deficiency of the Hartree-Fock method. They called it the optimized double configuration (ODC) method. It has recently been used to study the system F + Li2 20 and was also used as a starting point in the Cl calculations on KrF2.33... 

Curves that go beyond the Flartree-Fock method have been calculated for certain systems, and the list grows monthly. Of special interest is the series on ground [62-64] and excited states [63, 64] of CO, on NaLi and NaLi+ using an extended Flartree-Fock method with optimized double-valence configurations [65], HeLi by a valence-bond method [66], and so on. A quite complete listing of all nonempirical potential-energy curves calculated through 1967 is included in the NBS report [33]. 

Figure 3.7 Optimized adsorption configurations of sulfate over the Pt(lll) surface using (a) a vacuum model, (b) a partially solvated model used in the electric field model, and (c) a fully solvated model used in double reference method.

As the next examples show, the provisional stmcture may contain one or more inner atoms with less than octets of valence electrons. These provisional stmctures must be optimized in order to reach the most stable molecular configuration. To optimize the electron distribution about an inner atom, move electrons from adjacent outer atoms to make double or triple bonds until the octet is complete. Examples and illustrate this procedure. 

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