Calculations of the low-lying excited states of the TiO2 molecule

Abstract

We present calculations of the lowest excited electronic states of the TiO2 molecule. These are computed using several correlated wavefunction response based methods, as well as time-dependent density functional response theory using a range of functionals. Surprisingly lower cost wavefunction based methods, in particular the second-order CC2 and CIS(D) methods, completely fail to describe the lowest 1B2 and 1A2 states of the molecule. Density functional methods fare better but still show considerable variation amongst functionals. Thus TiO2 provides a strenuous test for correlated excited state methods.