Contracted GTOs segmented contraction

There are two different ways of contracting a set of primitive GTOs to a set of contracted GTOs segmented and general contraction. Segmented contraction is the... 

Most calculations today are done by choosing an existing segmented GTO basis set. These basis sets are identihed by one of a number of notation schemes. These abbreviations are often used as the designator for the basis set in the input to ah initio computational chemistry programs. The following is a look at the notation for identifying some commonly available contracted GTO basis sets. 

Let us see how we may generate a segmented basis set from the primitive functions in Table 8.2. We would like to combine these functions into a smaller set of contracted GTOs that reproduces as accurately as possible the Hartree-Fock orbitals and which at the same time has the flexibility to describe the changes that occur in the valence region upon formation of chemical bonds. Clearly, some compromises must be made since an accurate representation of the Hartree-Fock orbitals requires the use of generally contracted GTOs. 

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