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

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. © 2010 American Institute of Physics.