Density functional calculation of the electronic absorption spectrum of Cu{sup +} and Ag{sup +} aqua ions
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)
The UV absorption of aqueous Cu{sup +} and Ag{sup +} has been studied using Time Dependent Density Functional Theory (TDDFT) response techniques. The TDDFT electronic spectrum was computed from finite temperature dynamical trajectories in solution generated using the Density Functional Theory (DFT) based Ab Initio Molecular Dynamics (AIMD) method. The absorption of the two ions is shown to arise from similar excitation mechanisms, namely transitions from d orbitals localized on the metal center to a rather delocalized state originating from hybridization of the metal s orbital to the conduction band edge of the solvent. The ions differ in the way the spectral profile builds up as a consequence of solvent thermal motion. The Cu{sup +} absorption is widely modulated, both in transition energies and intensities by fluctuations in the coordination environment which is characterized by the formation of strong coordination bonds to two water molecules in an approximately linear geometry. Though, on average, absorption intensities are typical of symmetry forbidden transitions of metal ions in the solid state, occasionally very short (<100 fs) bursts in intensity are observed, associated with anomalous Cu-H interactions. Absorption by the Ag{sup +} complex is in comparison relatively stable in time, and can be interpreted in terms of the energy splitting of the metal 4d manifold in an average crystal field corresponding to a fourfold coordination in a distorted tetrahedral arrangement. Whereas the spectral profile of the Ag{sup +} aqua ion is in good agreement with experiment, the overall position of the band is underestimated by 2 eV in the BLYP approximation to DFT. The discrepancy with experiment is reduced to 1.3 eV when a hybrid functional (PBE0) is used. The remaining inaccuracy of TDDFT in this situation is related to the delocalized character of the target state in d{yields}s transitions.
- OSTI ID:
- 20658139
- Journal Information:
- Journal of Chemical Physics, Vol. 121, Issue 23; Other Information: DOI: 10.1063/1.1818676; (c) 2004 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION
ABSORPTION SPECTRA
CATIONS
CHEMICAL BONDS
COMPARATIVE EVALUATIONS
COPPER
COPPER IONS
CRYSTAL FIELD
DENSITY FUNCTIONAL METHOD
EV RANGE 01-10
FORBIDDEN TRANSITIONS
ION DENSITY
MATHEMATICAL SOLUTIONS
MOLECULAR DYNAMICS METHOD
PHOTOCHEMISTRY
SILVER IONS
SOLVENTS
ULTRAVIOLET SPECTRA