Long-range corrected hybrid functionals that employ a nonempirically tuned range-separation parameter have been demonstrated to yield accurate ionization potentials and fundamental gaps for a wide range of finite systems. Here, we address the question of whether this high level of accuracy is limited to the highest occupied/lowest unoccupied energy levels to which the range-separation parameter is tuned or whether it is retained for the entire valence spectrum. We examine several π-conjugated molecules and find that orbitals of a different character and symmetry require significantly different range-separation parameters and fractions of exact exchange. This imbalanced treatment of orbitals of a different nature biases the resulting eigenvalue spectra. Thus, the existing schemes for the tuning of range-separated hybrid functionals, while providing for good agreement between the highest occupied energy level and the first ionization potential, do not achieve accuracy comparable to reliable G 0W 0 computations for the entire quasiparticle spectrum.
|Physical Review B - Condensed Matter and Materials Physics
|Published - Nov 8 2012
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics