Xxvii theory

The relations shown in Table XXVII-2 tell nothing about the theory giving the interatomic energy as a function of volume. We cannot get nearly so far with this as we could with ionic crystals. There the attractive forces between ions were simple Coulomb forces,. which we could calculate exactly, though we had to approximate the repulsive forces by an empirical formula, which we took to be an inverse power term. For metals, the theory of the metallic bond is so complicated that the forces... 

For convenience we continue the development on closed shell systems. Other systems are discussed in Sections XX and XXI. The theory is still based on non-localized H.F. orbitals and SCF MO s which satisfy Eqs. (12). The results are transformed into the localized description in Sections XXVII and XXVIII. 

The H2 example indicates that in intermediate cases, the /< may be examined and the starting <(> decided upon. Fortunately, thk problem does not come up in obtaining most binding energies (r = Tg) and in non-bonded interactions. For example, the composite system of two Ne atoms (starting with MO s) remains a single determinant at all r owing to exclusion efEects . The raany-electron theory for closed shells can also be applied to this system as well as to non-bonded interactions between the bonds of say a saturated hydrocarbon (see Sections XXVII and XXVIII). 

This discussion applies to molecules starting with pg in the SCF MO description. Then, even for large saturated molecules, there will be a for every molecular orbital pair (ij). However, the theory will be transformed in Section XXVII lielow into the localized orbitals description. Then the MO localized correlation functions... 

The procedures outlined above for atoms also apply to small molecules, e.g. LiH, Lig, Ng, HF, Fj, etc. For these, the theory starts with H.F. SCF MO s the l /s refer to MO pairs. The inner shells, however, can be taken directly from free atoms after an equivalent orbital transformation has been performed on say the (l(r,) (lmedium effects on the innermost shells... 

As a result of an analysis of numerous data on the direction of hydrolysis reactions of ethers and amides which proceed via formation of the type XXVII intermediates, a simple phenomenological theory was evolved of stereoelectronic control of fragmentation of tetrahedral intermediates [120, 121]. This theory rests on the classical notion of the hybrid orbitals of electron lone pairs (ELP) of heteroatoms. 

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