Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 84: Density functional theory and beyond for real materials IV

O 84.5: Vortrag

Freitag, 26. März 2010, 12:15–12:30, H34

Assessing the random phase approximation for weakly bonded molecules — •Xinguo Ren, Patrick Rinke, and Matthias Scheffler — Fritz-Haber-Institut der MPG, 14195 Berlin, Germany

The random phase approximation (RPA) to the electronic correlation energy has generated increasing interest in recent years due to several of its attractive features. One of these is the automatic and seamless inclusion of van der Waals (vdW) interactions, which makes the RPA free of limitations that empirical vdW correction schemes may suffer from. However, RPA is still an approximate theory, and the treatment of vdW will not be perfect. In addition, RPA calculations are presently performed non-self-consistently with input orbitals from a preceding Hartree-Fock (HF) or standard density functional theory (DFT) calculation. For a systematic assessment of the RPA’s performance for vdW interactions, we applied our recent implementation of the RPA [1] to the molecular S22 benchmark set [2], which comprises 22 weakly bonded complexes of different nature. Different DFT/HF orbitals have been used to demonstrate the orbital dependence of RPA. We observe a systematic underbinding of the RPA in all cases, whereby the amount of underbinding depends noticeably on the input orbitals. A detailed analysis reveals that both the exchange and the correlation part of the RPA contribute to this dependence, but in a somewhat counteracting manner. [1] V. Blum et al., Comp. Phys. Comm. 180, 2175 (2009). [2] P. Jurečka et al. , Phys. Chem. Chem. Phys. 8, 1985 (2006).