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

被引:41
作者
Hellgren, Maria [1 ]
von Barth, Ulf [1 ]
机构
[1] Lund Univ, Dept Math Phys, Inst Phys, S-22362 Lund, Sweden
关键词
atom-photon collisions; autoionisation; beryllium; density functional theory; eigenvalues and eigenfunctions; HF calculations; neon; photoexcitation; photoionisation; LINEAR-RESPONSE; HARTREE-FOCK; SYSTEMS; APPROXIMATION; POTENTIALS; ENERGIES; PHOTOIONIZATION; RESONANCES; EXCITATION; HELIUM;
D O I
10.1063/1.3179756
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
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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页数:13
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