Charge-transfer excitations in uranyl tetrachloride ([UO2Cl4]2-): how reliable are electronic spectra from relativistic time-dependent density functional theory?
Four-component relativistic time-dependent density functional theory (TD-DFT) is used to study charge-transfer (CT) excitation energies of the uranyl molecule as well as the uranyl tetrachloride complex. Adiabatic excitation energies and vibrational frequencies of the excited states are calculated for the lower energy range of the spectrum. The results for TD-DFT with the CAM-B3LYP exchange-correlation functional for the [UO(2)Cl(4)](2-) system are in good agreement with the experimentally observed spectrum of this species and agree also rather well with other theoretical data. Use of the global hybrid B3LYP gives qualitatively correct results, while use of the BLYP functional yields results that are qualitatively wrong due to the too low CT states calculated with this functional. The applicability of the overlap diagnostic of Peach et al. (J. Chem. Phys.2008, 128, 044118) to identify such CT excitations is investigated for a wide range of vertical transitions using results obtained with three different approximate exchange-correlation functionals: BLYP, B3LYP, and CAM-B3LYP.
Amsterdam Center for Multiscale Modeling, Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Paweł
P
Tecmer
Radovan
R
Bast
Kenneth
K
Ruud
Lucas
L
Visscher
D002712:Chlorides / Q000737:chemistry*; D004735:Energy Transfer; D008958:Models, Molecular; D011789:Quantum Theory; D055672:Static Electricity; D013816:Thermodynamics; D013997:Time Factors; D017974:Uranium Compounds / Q000737:chemistry*; D014732:Vibration
D002712:Chlorides; D017974:Uranium Compounds