Description of core excitations by time-dependent density functional theory with local density approximation, generalized gradient approximation, meta-generalized gradient approximation, and hybrid functionals

✍ Scribed by Yutaka Imamura; Takao Otsuka; Hiromi Nakai

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 143 KB
• Volume: 28
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.20724

✦ Synopsis

Abstract

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