HLSP-method

The Heitier-London-Slater-Pauling (HLSP) method. This method, which was developed originally by Slater as a generalization of Heitler and London s treatment of the hydrogen molecule, was... 

In bond orbital theory the wave functions of the molecule are derived from the wave functions associated with the different bonds of a molecule, i.e. from the bond orbitals. In the LCBO model the molecular orbitals are a linear combination of bond orbitals which in turn are a combination of the atomic orbitals or hybrids forming the bond in question [2b]. In the HLSP-method the many-electron wave functions are a sum of product functions which contain a Heitler and London type of factor (space function and spin function) for each bond of the molecule. 

Of these two schemes, it appears that the standard tableaux functions have properties that allow more efficient evaluation. This is directly related to the occurrence of the J f on the outside of OAfVAf. Tableau functions have the most antisymmetry possible remaining after the spin eigenfunction is formed. The HLSP functions have the least. Thus the standard tableaux functions are closer to single determinants, with their many properties that provide for efficient manipulation. Our discussion of evaluation methods will therefore be focused on them. Since the two sets are equivalent, methods for writing the HLSP functions in terms of the others allow us to compare results for weights (see Section 1.1) of bonding patterns where this... 

To obtain the symmetry functions in terms of HLSP functions we can transform the standard tableaux functions using the methods of Chapter 5. The transformation matrix is given in Eq. (5.128) ... 

The HLSP function form of this wave function is easily obtained with the method of Section 5.5.5,... 

Slater s bond eigenfunctions constitute one choice (out of an infinite number) of a particular sort of basis function to use in the evaluation of the Hamiltonian and overlap matrix elements. They have come to be called the Heitler-London-Slater-Pauling (HLSP) functions. Physically, they treat each chemical bond as a singlet-coupled pair of electrons. This is the natural extension of the original Heitler-London approach. In addition to Slater, Pauling[12] and Eyring and Kimbal[13] have contributed to the method. Our following description does not follow exactly the discussions of the early workers, but the final results are the same. 

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