Walsh Diagrams: Molecular Orbital and Structure Computational Chemistry Exercise for Physical Chemistry

The increasing importance of computational chemistry in modern chemistry provides an impetus to increase the incorporation of computational exercises in the undergraduate chemistry curriculum. Herein, a computational chemistry exercise that can be used in a physical chemistry course is described. In this exercise, students build a series of AH(2) molecules in the computational chemistry software Spartan and construct Walsh diagrams for the molecules from calculations of the molecular orbital energies as a function of bond angle. The Walsh diagrams are then used to predict the bond angle of the ground state of each molecule. The exercise focuses on creating a connection between molecular orbital theory and molecular structure and investigating the effects of using different methods and basis sets on the molecular orbital energies. This exercise provides a means for students to visualize and explore the molecular orbitals of small molecules.