Heteronuclear diatomic molecule molecular orbital calculations

The molecular orbital energy-level diagrams of heteronuclear diatomic molecules are much harder to predict qualitatitvely and we have to calculate each one explicitly because the atomic orbitals contribute differently to each one. Figure 3.35 shows the calculated scheme typically found for CO and NO. We can use this diagram to state the electron configuration by using the same procedure as for homonuclear diatomic molecules. 

Molecular orbital calculations on heteronuclear diatomic molecules, hybridization, and estimation of net atomic charges from calculated electron densities... 

In this chapter we shall use lithium hydride, LiH, to discuss the application of the molecular orbital model to a heteronuclear diatomic molecule, and begin by outlining a very simple computational procedure that yields an approximate description of the molecular orbital containing the two valence electrons. We then go on to outline the application of Hartree-Fock (HF) calculations based on a wavefuntion for both the two valence and the two inner-shell electrons. The wavefunction obtained by such calculations indicate that the bonding molecular orbital must be written as a linear combination of the H I5 with both 2s and 2pa atomic orbitals on the Li atom. 

Heteronuclear diatomic molecules are not as symmetrical as homonuclear molecules, and we cannot evaluate coefficients in LCAO molecular orbitals by requiring that the orbitals have the proper symmetry. Variational, SCF, or density functional calculations must be used to evaluate the coefficients. 

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