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Abstract
A typical quinacridone pigment, PV19, has been used to analyze the impact of several computational parameters on the UV/vis absorption band shape in solution, simulated using density functional theory and timedependent density functional theory levels of approximation. These encompass, (i) the choice of exchangecorrelation functional, (ii) the basis set, (iii) the method for nonequilibrium optimization of the excited state geometry, (iv) the approach for evaluating the vibronic band structure, (v) the peak broadening, and (vi) the scaling of the harmonic vibrational frequencies. Among these, the choice of exchangecorrelation functional is certainly of the most importance because it can drastically modify the spectral shape. In the case of PV19, the M052X and to a lesser extent CAMB3LYP XC functionals are the most efficient to reproduce the vibronic structure, confirming the important role of exact HartreeFock exchange. Still, these functionals are not the most reliable to predict the excitation energies and oscillator strengths, for which M05, a functional with less HF exchange, performs better. For evaluating the vibronic structure, the simple gradient method, where only one step of geometry optimization of the excited state is carried out and the gradients are used to evaluate the HuangRhys factors as well as to determine the excited state geometries produces a spectrum that is very similar to the ones obtained with the more involved Duschinsky and geometry methods, opening the way to a fast simulation of the UV/vis absorption spectra of pigments and dyes. Then, the effect of scaling the calculated vibrational frequencies to account for anharmonicity effects as well as for limitation of the method also impacts the shape of the vibronic spectrum and this effect depends on the method used to determine the HuangRhys factors. Indeed, scaling the vibrational frequencies by a factor which is typically smaller than 1.0 results in a relative decrease of the 01 peak intensity with respect to the 00 band when optimizing the geometry of the excited state whereas the effect is opposite and magnified if using the gradient method. This journal is
Original language  English 

Pages (fromto)  444456 
Number of pages  13 
Journal  Photochemical and Photobiological Sciences 
Volume  14 
Issue number  2 
DOIs  
Publication status  Published  4 Feb 2015 
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PAI n°P7/05  FS2: Functional Supramolecular Systems (FS2)
CHAMPAGNE, B., De Vos, D., Van der Auweraer, M., Jérôme, C., Lazzaroni, R., Marin, G., Jonas, A., Du Prez, F., Vanderzande, D., Van Tendeloo, G., Van Speybroeck, V., NENON, S. & STAELENS, N.
1/04/12 → 30/09/17
Project: Research

TINTIN  ARC 09/1423: Molecular TINkertoys for OpToelectronics and SpINtronics  TINTIN
BONIFAZI, D., CHAMPAGNE, B., FORENSI, S., SEGERIE, A. & Melinte, S.
1/09/09 → 31/08/14
Project: Research
Equipment

High Performance Computing Technology Platform
Benoît Champagne (Manager)
Technological Platform High Performance ComputingFacility/equipment: Technological Platform