Molecular Electronic Excitation Energies from Range-separated TD-DFT and Bethe-Salpeter Kernels

Elisa Rebolini
LCT, Université Pierre et Marie Curie, Paris, France.
rebolini@lct.jussieu.fr
Jeudi 11 Juillet 2013, 11^h00
bibliothèque LCT, tour 12 - 13, 4e étage

In the past years, time-dependent density functional theory (TDDFT)[1] within the usual local (LDA) or semi-local (GGA) approximations has become very popular to calculate excitation energies of medium-sized systems because of its low computational cost and good accuracy. It has been shown very reliable in predicting excitation energies to the low-lying valence states but still present several shortcomings, especially concerning the underestimation of the high-lying Rydberg excitation energies, a poor description of charge transfer excitations and the lack of double or higher order excitations. Range separation of the electronic interaction has been proposed as one way to correct these deficiencies and has been shown very efficient when applied to the exchange part of the functional to recover good Rydberg and charge transfer excitation energies[2, 3]. However, situations as the dissociation of the hydrogen molecule and the treatment of excitation with multiple character are still pathological in this approach. These problems have been attributed to a bad description of the correlation kernel which is frequency independent in TDDFT within the adiabatic approximation.
In this talk, I will present an extension of the range separation technique to the correlation kernel and I will show long-range correlation kernels inspired by the Bethe-Salpeter kernels from solid-state physics[4, 5].

REFERENCES

[1] M. E. Casida. Recent Advances in Density Functional Methods, Part I, page 155, D. P. Chong ed.; World Scientific, Singapore (1995)
[2] Y. Tawada, T. Tsuneda, S. Yanagisawa, T. Yanai, and K. Hirao. J. Chem. Phys. 120 8425 (2004)
[3] E. Rebolini, A. Savin, and J. Toulouse. Mol. Phys. (2013)
[4] G. Onida, L. Reining, and A. Rubio. Rev. Mod. Phys. 74 601 (2002)
[5] E. Rebolini, J. Toulouse, and A. Savin. Concepts and Methods in Modern Theoretical Chemistry, Vol. 1: Electronic Structure and Reactivity, Chapter 18, CRC Press (2013)