Exact-exchange kernel of time-dependent density functional theory: Frequency dependence and photoabsorption spectra of atoms

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Exact-exchange kernel of time-dependent density functional theory: Frequency dependence and photoabsorption spectra of atoms. / Hellgren, Maria; von Barth, Ulf.

I: Journal of Chemical Physics, Vol. 131, Nr. 4, 044110, 2009.

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TY - JOUR

T1 - Exact-exchange kernel of time-dependent density functional theory: Frequency dependence and photoabsorption spectra of atoms

AU - Hellgren, Maria

AU - von Barth, Ulf

PY - 2009

Y1 - 2009

N2 - 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.

AB - 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.

KW - photoexcitation

KW - autoionisation

KW - atom-photon collisions

KW - beryllium

KW - density functional

KW - theory

KW - eigenvalues and eigenfunctions

KW - neon

KW - HF calculations

KW - photoionisation

U2 - 10.1063/1.3179756

DO - 10.1063/1.3179756

M3 - Article

VL - 131

JO - Journal of Chemical Physics

T2 - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 4

M1 - 044110

ER -