Molecular design prototype molecules

In the above context, the perspective was one of how do we describe a molecule in terms of a graph however, it is the reverse mapping which leads to new molecular designs. So let us review quickly some basic features of graphs, specifically connected graphs, as molecular prototypes. 

In the literature the cluster model terms is perhaps more frequently used. However, the term cluster should be reserved for designating the experimentally existing atomic aggregates. Prototype molecules are those molecular systems, which may or may not exist experimentally, but they are designed to represent a characteristic portion of an extended system, such as a biological macromolecule, protein, crystal etc. 

In our previous work [23], we have investigated the use of distributed basis sets for molecular electronic structure calculations that is, basis sets which comprise a number of subsets each subset being centred on a different point in space. In approaching the Hartree-Fock limit, we have found that in addition to the usual atom-centred subsets, functions centred on the bond mid-point are also very useful. For the ground state of the boron fluoride molecule, which we use as a prototype in the present study, such a basis sets may be designated... 

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