Nitrogen diatomic molecule, orbitals

The advantages of INDO over CNDO involve situations where the spin state and other aspects of electron spin are particularly important. For example, in the diatomic molecule NH, the last two electrons go into a degenerate p-orbital centered solely on the Nitrogen. Two well-defined spectroscopic states, S" and D, result. Since the p-orbital is strictly one-center, CNDO results in these two states having exactly the same energy. The INDO method correctly makes the triplet state lower in energy in association with the exchange interaction included in INDO. 

The surface molecule model has been used to study chemisorption of hydrogen 47) and nitrogen 48) on tungsten (100). The parameters used in these calculations are collected in Table IV. Preliminary calculations on the diatomic molecules WH and WW showed that inclusion of tungsten 5 p orbitals is essential to produce a minimum in the energy/ distance curves. However, the repulsion due to inner electrons could be calculated by the empirical relationship ... 

The molecular orbital diagram for the nitrogen monoxide molecule is shown in Figure 4.6. The orbitals are produced from the same pairs of atomic orbitals as in the cases of the homonuclear diatomic molecules of Section 4.2. 

Diatomic molecules are still rather simple systems suitable for clarifying problems encountered in polyatomic molecules. Moreover, they give us additional information not obtainable from atomic calculations, Polarization functions represent a typical example. Since they correspond to orbitals unoccupied in atomic ground states, their exppnents cannot be estimated from atomic calculations. Among the calculations on diatomic molecules, very useful information on the problem of basis set composition was contributed by calculations reported by Cade, Huo, Wahl, Sales, Liu, Yoshimine and others " . Consider for example the results for the nitrogen molecules. Fig. 2.2 presents the dependence of the total energy and its components (ki-... 

In many cases the molecular orbitals for a heteronuclear diatomic molecule may be worked out in a straightforward manner as for hydrogen chloride. In others, however, certain difficulties arise and we shall take as an example the case of carbon monoxide, the structure of which has been the subject of much controversy. In carbon monoxide, as in the nitrogen molecule, there are fourteen valency electrons and Mullikan has formulated the structure of both molecules as... 

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