Correlation an Eight-Configuration Solution

What is obviously missing from the seven-configuration wavefunction described in the previous Subsection is some correlation across the plane of the nuclei for the two inner orbitals, analogous to that already included for the three valence pairs. The most economical way to provide this missing correlation is of course through the addition of a fully-symmetric configuration consisting of three symmetry-equivalent pairs of a orbitals and a pair of identical C3- and 7v-invariant n orbitals. 

Configuration overlaps for the seven-configuration GMCSC solution (/ bh=2.24 ao). 

The first seven configurations remain almost exclusively perfect-paired. As for the eighth configuration, it too turns out to be almost exclusively perfect-paired the coefficient of the perfectly-paired YK spin function is in fact 0.982. In any case, the fact that its first two orbitals are identical rules out nine YK spin functions out of fourteen, and symmetry requirements further mandate three linear constraints on the coefficients of the five allowed spin functions, so that only two of them are truly independent. Anyway, one can legitimately conclude that the seven-configuration wavefunction is qualitatively robust with respect to the inclusion of this kind of inner shell correlation. 

The three unique orbitals in the last of the eight configurations are drawn in Fig. 6. A comparison with Fig. 3 will confirm that corresponding valence orbitals in the two configurations are fairly similar, supporting the claim that this 

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