Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 80: Challenges in semiconductor theory
HL 80.2: Talk
Thursday, March 19, 2015, 15:15–15:30, EW 015
Towards simple orbital-dependent density functionals for molecular dissociation — •Igor Ying Zhang1, Patrik Rinke1,2, and Matthias Scheffler1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, 12149 Berlin-Dahlem — 2COMP/Department of Applied Physics, Aalto University School of Science, P.O. Box 11100, FI-00076 Aalto, Finland
Density functional theory (DFT) is one of the leading first-principles electronic-structure theories. However, molecular dissociation remains a challenge, because it requires a well-balanced description of the drastically different electronic structure at different bond lengths. One typical and well-documented case is the dissociation of both H2+ and H2, for which all popular DFT functionals fail [1]. We start from the Bethe-Goldstone equation to propose a simple orbital-dependent correlation functional which generalizes the linear adiabatic connection approach. The resulting scheme is based on second-order perturbation theory (PT2), but includes the self-consistent coupling of electron-hole pairs, which ensures the correct H2 dissociation limit and gives a finite correlation energy for systems with a (near)-degenerate energy gap. This coupling PT2-like (CPT2) approximation delivers a significant improvement over all existing functionals for both H2 and H2+ dissociation. We will demonstrate the reason for this improvement analytically for H2 in a minimal basis.[1] A. J. Cohen et al., Chem. Rev. 112 289 (2012). [2] F. Caruso et al., Phys. Rev. Lett. 110 146403 (2013).