Generation with overlapping atoms

A successor of CONGEN is Generation with Overlapping Atoms (GENOA), which introdnced several improvements to functionality and interactivity [3]. GENOA allows for the overlap of substructures as well as for defining limitations for a series of possible snbstructures. It reduces the number of constraints and gives the ability to retrieve intermediate resnlts. 

Generation with Overlapping Atoms (GENOA) is software for generating all isomers for a given structure and is a successor of CONGEN with improved constraint handling. 

A complete orbital overlap view of methane appears in Figure 10-10. Hybridization gives each carbon orbital a strongly favored direction for overlap with an atomic 1. S orbital from an approaching hydrogen atom. Four such interactions generate four localized bonds that use all the valence electrons of the five atoms involved. 

We generate hybrid orbitals on inner atoms whose bond angles are not readily reproduced using direct orbital overlap with standard atomic orbitals. Consequently, each of the electron group geometries described in Chapter 9 is associated with its own specific set of hybrid orbitals. Each type of hybrid orbital scheme shares the characteristics described in our discussion of methane ... 

One way to help a basis set have smaller BSSE is to use localized orbitals or bond orbitals. These functions should have inherently less overlap with adjacent atomic sites. We will explore this in more detail later, but the issue is often complicated by problems in generating these localized functions and calculating molecular properties. 

Any combination of atomic and hybrid orbitals may overlap to form bonds. For example, the four sp orbitals of carbon can combine with four chlorine 3p orbitals, resulting in tetrachloromethane, CCI4. Carbon-carbon bonds are generated by overlap of hybrid orbitals. In ethane, CH3-CH3 (Figure 1-19), this bond consists of two sp hybrids, one from each of two CH3 units. Any hydrogen atom in methane and ethane may be replaced by CH3 or other groups to give new combinations. 

As described in several review articles [409,452-454] and books [10,13,15], this is basically due to the inherent features of the d -p bond in phosphazenes, which allows the permanent overlapping of the 2pj orbital of the skeletal nitrogens with any one of the 3p orbitals of the phosphorus atoms [455]. Such a high chain flexibihty generated very low glass transition temperatures in these polymers, which can reach values of about -100 °C when suitable flexible substituent groups (e.g. n-butanol) are present on the skeletal phosphorus [274]. 

Each of the carbon atoms in butadiene has a p orbital oriented to overlap with those on neighboring carbon atoms, generating a set of four MOs, of which one is shown. 

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