A full MCVB calculation

The author and his students have used the term multiconfiguration valence bond (MCVB) to describe a linear variation calculation involving more than one VB structure (function). This practice will be continued in the present book. Other terms have been used that mean essentially the same thing[34]. We defer a fuller 

In the present case we have ten AO basis functions, and these provide a set of 55 symmetric (singlet) spatial functions. Only 27 of these, however, can enter into functions satisfying the spatial symmetry, of the ground state of the H2 molecule. Indeed, there are only 14 independent linear combinations for this subspace from the total, and, working in this subspace, the linear variation matrices are only 14 x 14. We show the energy for this basis as the lowest energy curve in Fig. 2.8. We will discuss the other curves in this figure later. 

Compare with the term full Cl used in the MO regime. 

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A full MCVB calculation on BeH with the above basis yields 504 doublet standard tableaux functions, and these combine into 344 symmetry functions. In Table 10.7 we give some details of the results with experimental values for comparison. The calculated is within 0.1 eV of the experimental value, the values of... 

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