Practical Training in Simple Hiickel Theory: Matrix Diagonalization for Highly Symmetric Molecules and Visualization of Molecular Orbitals

At an advanced stage of learning quantum chemistry, undergraduate students usually encounter simple Hiickel-molecularorbital (HMO) theory, whose primitive approach gives very useful insight into the electronic structure of pi-conjugated molecules. However, on one hand, computational HMO software, when programmed without using molecular symmetry, does not necessarily output chemically reasonable shapes of degenerate molecular-orbitals in benzene. On the other hand, separately inputting the molecular symmetry into the HMO calculation is mathematically redundant (i.e., duplicate information input). To solve this problem, in this study, a Microsoft Excel macro for obtaining reasonable HMOs of highly symmetric molecules such as benzene was developed. Furthermore, two other Excel macros for readily drawing quantitative contour plots of HMOs were created as student friendly tools. The practical training in simple HMO theory proposed in the present report using these three macros will be very useful for undergraduate teaching of quantum chemistry in terms of clearly showing the theoretical concept.