Computation of large systems with an economic basis set: Systems in excited states

An economic basis set for ab initio calculations of systems in excited states has been studied. The economic basis set, in which the polarization functions are applied only to oxygen (O), while the 6-31G basis set is used for carbon (C) and hydrogen (H), is shown to save considerable computing time and to give reliable geometric and frequency measurements. In addition, the economic basis set has been considered for obtaining reliable excitation energies, with the correction factor, using high-level single-point energy calculations. This study is expected to shed light on basis set selection for computations of large systems in excited states.