Exact-exchange kernel of time-dependent density functional theory: frequency dependence and photoabsorption spectra of atoms
In this work we have calculated excitation energies and photoionization cross sections of Be and Ne in the exact-exchange (EXX) approximation of time-dependent density functional theory (TDDFT). The main focus has been on the frequency dependence of the EXX kernel and on how it affects the spectrum...
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Published in | The Journal of chemical physics Vol. 131; no. 4; p. 044110 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
United States
28.07.2009
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Online Access | Get more information |
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Summary: | In this work we have calculated excitation energies and photoionization cross sections of Be and Ne in the exact-exchange (EXX) approximation of time-dependent density functional theory (TDDFT). The main focus has been on the frequency dependence of the EXX kernel and on how it affects the spectrum as compared to the corresponding adiabatic approximation. We show that for some discrete excitation energies the frequency dependence is essential to reproduce the results of time-dependent Hartree-Fock theory. Unfortunately, we have found that the EXX approximation breaks down completely at higher energies, producing a response function with the wrong analytic structure and making inner-shell excitations disappear from the calculated spectra. We have traced this failure to the existence of vanishing eigenvalues of the Kohn-Sham non-interacting response function. Based on the adiabatic TDDFT formalism we propose a new way of deriving the Fano parameters of autoionizing resonances. |
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ISSN: | 1089-7690 |
DOI: | 10.1063/1.3179756 |