Atomic pseudopotentials for reproducing π-orbital electron behavior in sp2 carbon atoms

A pseudopotential system for an sp(2) carbon atom is built and tested as a building block for various pseudohydrocarbon polyenes and polycyclic aromatic hydrocarbons. This pseudosystem has a central charge of Z = 1; it contains only one electron. It is employed in ab-initio calculations in which several physical characteristics including the orbital energies and first ionization energy, as well as first excitation energy and UV spectra, are found to be well-reproduced by the pseudosystem. Remarkably, not only are the pi excitation energies in good agreement with the reference calculations, but also transition densities and intensities, confirming that the virtual space obtained with the pseudopotentials is of excellent quality. Finally, this approach is capable of reproducing the pi electron systems of small or large, planar or nonplanar hydrocarbons at low computational cost.