Purely Covalent Singlet and Triplet Repulsive States

1 Purely Covalent Singlet and Triplet Repulsive States 

In the VB framework, some particular notations are traditionally employed to designate the various energies and matrix elements  

Q is the electronic energy of a single determinant ab, K is the spin exchange term that will be dealt with later, and Sat is the overlap integral between the two AOs a and b. 

FIGURE 3.3 Energy curves for H2 as a function of internuclear distance. The curves displayed, from top to bottom, correspond to the triplet state, Ty, the quasiclassical state, Fqc, the HL state, FHl and the exact full (full Cl) curve, i exact- 

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