Alternative Title

Multi-Reference Systems in Organic and Inorganic Chemistry

Subject Area



The geometries, chemical properties, and reactivities of molecules are determined by their electronic structure. The field of ab initio computational chemistry works to calculate the kinetic and potential energies between the nuclei and electrons of a molecule. These calculations usually begin with the determination the electronic ground state.

Molecules that cannot be adequately described with a single, ground state configuration are called \textit{multi-reference systems}, which require the calculation of a linear combination of all pertinent electronic configurations, with a corresponding increase in computational cost. This is not `black box' methodology, because solving these systems requires a good understanding of the chemistry being described, so that the important configurations among millions of possibilities can be selected. Their multi-reference character also makes them some of the most interesting molecules in chemistry.

In this dissertation, we have studied ultra-long CC bonds in simple and unique organic molecules, biradical pancake bonded species, fluxional bridged annulenes, and covalently bonded transition metal diatoms.

We find that CC ultra-long bonds and electrostatic pancake bonding interactions can be described by single-reference methods, but that fluxional bridged annulenes require multi-reference methods.

Transition metal diatoms can only be described by multi-reference methods. We determined which methods, basis sets, and active spaces work best in each of the 30 cases.

Degree Date

Spring 5-19-2018

Document Type


Degree Name





Dieter Cremer

Second Advisor

Elfriede Kraka

Third Advisor

Michael Lattman

Number of Pages




Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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