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Description of core excitations by time‐dependent density functional theory with local density approximation, generalized gradient approximation, meta‐generalized gradient approximation, and hybrid functionals
Author(s) -
Imamura Yutaka,
Otsuka Takao,
Nakai Hiromi
Publication year - 2007
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20724
Subject(s) - time dependent density functional theory , hybrid functional , local density approximation , density functional theory , excitation , atom (system on chip) , physics , core (optical fiber) , atomic physics , quantum mechanics , computer science , embedded system , optics
Time‐dependent density functional theory (TDDFT) is employed to investigate exchange‐correlation‐functional dependence of the vertical core‐excitation energies of several molecules including H, C, N, O, and F atoms. For the local density approximation (LDA), generalized gradient approximation (GGA), and meta‐GGA, the calculated X1s→π* excitation energies (X = C, N, O, and F) are severely underestimated by more than 13 eV. On the other hand, time‐dependent Hartree‐Fock (TDHF) overestimates the excitation energies by more than 6 eV. The hybrid functionals perform better than pure TDDFT because HF exchange remedies the underestimation of pure TDDFT. Among these hybrid functionals, the Becke‐Half‐and‐Half‐Lee‐Yang‐Parr (BHHLYP) functional including 50% HF exchange provides the smallest error for core excitations. We have also discovered the systematic trend that the deviations of TDHF and TDDFT with the LDA, GGA, and meta‐GGA functionals show a strong atom‐dependence. Namely, their deviations become larger for heavier atoms, while the hybrid functionals are significantly less atom‐dependent. © 2007 Wiley Periodicals, Inc. J Comput Chem 2007