From small molecules to solid-state materials: A brief discourse on an example of carbon compounds

In this chapter, we will demonstrate how to use molecular orbital theory and band theory to understand the electronic structure of carbon-based molecules and materials. At first, we overview the well-developed modeling methods, such as cluster models, QM/MM models, and periodic models. We then demonstrate how to construct the molecular orbitals for small molecules from the linear combination of atomic orbitals, and extend the idea to materials. Moreover, the impact of physical effects on the electronic structure of carbon materials, such as stacking and rolling-up, is also discussed. Finally, the cycloaddition reaction on sp2 hybridized CC bonds is taken as an example to highlight the importance of partition and hybrid schemes in ONIOM.