Excitation energies from time-dependent density-functional formalism for small systems

EPL-EUROPHYS LETT 57, 683 - 689 (2002)

Excitation energies from time-dependent density-functional formalism for small systems

F. Aryasetiawan, O. Gunnarsson, A. Rubio

As a test of the time-dependent local-density approximation (TDLDA), we study the 1Σg+1Σu+ excitation of H2 as a function of the nuclear distance d. We find rather accurate results for intermediate d but not for small and large d. At large d, TDLDA fails due to the strong non-locality and energy dependence of the exact functional. The spin-dependent formalism gives a qualitative improvement for large d. To analyze the results, we compare with the 2s → 2p excitation for He, Li and Be for small and intermediate d and with the Hubbard model for large d. The fairly accurate results for Li and Be are related to the accuracy of the ground-state formalism for a few electrons.

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http://dx.doi.org/10.1209/epl/i2002-00517-6

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