Time dependent density functional theory study of the electronic potential energy curves and excitation spectrum of the oxygen molecule

Guan, Jingang, Wang, Fan, Ziegler, Tom and Cox, Hazel (2006) Time dependent density functional theory study of the electronic potential energy curves and excitation spectrum of the oxygen molecule. Journal of Chemical Physics, 125 (4). 044314. ISSN 0021-9606

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Abstract

Orbital energies, ionization potentials, molecular constants, potential energy curves, and the excitation spectrum of O2 are calculated using time - dependent density functional theory (TDDFT) with Tamm-Dancoff Approximation (TDA). The calculated negative highest occupied molecular orbital energy (-HOMO) is compared with the energy difference ionization potential for five exchange correlation functionals consisting of: the local density approximation (LDAxc); gradient corrected Becke exchange plus Perdew correlation (B88X+P86C); gradient regulated asymptotic correction (GRAC); statistical average of orbital potentials (SAOP); and van Leeuwen and Baerends asymptotically correct potential (LB94). The potential energy curves calculated using TDDFT with the TDA at internuclear distances from 1.0 to 1.8 , are divided into three groups according to the electron configurations. The 1u41g2 electron configuration gives rise to the X3g, a1g, and b1g+ states; the 1u31g3 electron configuration gives rise to the c1u, C3u, and A3u+ states; and the B3u, A1u, and f1u+ states are determined by the mixing of two or more electron configurations. The excitation spectrum of the oxygen molecule, calculated with the aforementioned exchange correlation functionals, shows that the results are quite sensitive to the choice of functional. The LDAxc and the B88X+P86C functionals produce similar spectroscopic patterns with a single strongly absorbing band positioned at 19.82 eV and 19.72 eV, respectively, while the asymptotically corrected exchange correlation functionals of the SAOP and the LB94 varieties yield similar excitation spectra where the computed strongly absorbing band is located at 16.09 eV and 16.42 eV, respectively. However, all of the exchange correlation functionals yield only one strongly absorbing band (oscillator strength greater than 0.1) in the energy interval of 0 eV to 20 eV, which is assigned to a X3g to 3u transition. Furthermore, the oxygen molecule has a rich spectrum in the energy range of 14 eV to 20 eV and no spin allowed absorption bands are predicted to be observed in the range from 0 eV to 6 eV.

Item Type: Article
Additional Information: HC is the corresponding author. First application of open-shell spin-flip TDDFT to the oxygen molecule. TZ and his post-doc FW implemented the spin-flip formalism and JG (my post-doc) tested the implementation and performed a functional evaluation. Paper written and submitted by JG and HC.
Schools and Departments: School of Life Sciences > Chemistry
Depositing User: Jingang Guan
Date Deposited: 06 Feb 2012 21:25
Last Modified: 30 Mar 2012 11:09
URI: http://sro.sussex.ac.uk/id/eprint/31156
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