Molecular orbital theory is a present day predictive tool used to further our understanding of chemical systems and their interactions. To most, the Schrödinger atomic orbital solutions are applied as the general basis set to obtain the commonly recognized s, p, d, and f orbitals. Its applicability is notable throughout all fields of chemistry, the most flexible applications arguably being found in the study of inorganic complexes. Special cases involve heavy transition compounds, of which the behavior of contained electrons is crucially affected due to large nuclear charges, and relativistic effects become necessary to consider. Due to such situations relativistic corrections have been sought out through the Dirac theory approach. Application of the relativistic Hamiltonian allowed for reconstruction of each mathematical orbital for an accurate investigation not only in heavy element chemistry, but for small nuclear charged systems too. While many undergraduate students do not formally get introduced to the solutions of either set of linear combinations, the radial and spherical components of each basis are plotted for comparison between theories. As in general chemistry these solutions were used to investigate orbital energy diagrams across the periodic table. While the overwhelming majority of chemistry does not abide to a one electron basis set, calculations in first and second order perturbation and variational treatment have been implemented to acquire electron density plots of small chemical systems (i.e. H<sub>2</sub>) to further distinguish differences between each approach.

Expansion of molecular orbital theory: Application of Dirac's theory

251st National Meeting (2016)

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