TIME DEPENDENT APPROACHES FOR VIBRONIC SPECTRA AND INTERNAL CONVERSION RATES IN LARGE SYSTEMS Fabrizio Santoro Italian National Research Council, ICCOM-CNR, Area della Ricerca del CNR di Pisa, fabrizio.santoro@iccom.cnr.it. Thanks to the recent developments in electronic structure methods (mostly TD-DFT) and to the ever growing computational power the characterization of equilibrium geometries and Hessians of (mono-) excited electronic states of sizable molecules (dozens of heavy atoms) is nowadays straightforward in many cases. This has called for the development of automatic and user friendly methods for the computation of the line shapes of electronic spectra, able to extend the popular linear vibronic coupling model (LVC) to account for quadratic couplings (quadratic vibronic coupling, QVC). For harmonic systems with negligible nonadiabatic couplings path integral techniques [1-6] allow to derive an analytical expression of the finite-temperature time-correlation function whose Fourier transform gives the electronic spectrum. This quantum dynamical approach is very effective and delivers fully-converged spectra at almost no computational cost (few minutes of calculations), accounting for temperature, Duschinsky [1] and Herzberg-Teller effects [2-6]. The same kind of techniques permit to straightforwardly compute non-radiative rate constants driven by nonadiabatic couplings within Fermi Golden Rule [7], accounting for the effect of the bath of the vibronic states due to the whole set of molecular vibrations. We will show some applications made in our group. For systems where nonadiabatic couplings cannot be treated in a perturbative way, hierarchical representations of the Hamiltonian offer an effective route to reduce the dimensionality of the system and the computational cost of the quantum-dynamical simulations. Based on the original idea presented in refs [8-9] for LVC Hamiltonians, we proposed a method to build up the hierarchy of effective modes in QVC models [10-11]. This approach can be applied to the simulation of several electronic spectra. We show that in circular dichroism of exciton coupled dimers it is able to reproduce the characteristic alternation of positive and negative vibronic bands and it provides a robust simplified model to interpret the spectra in terms of the symmetry properties of pseudo-eigenfunctions of the effective modes [12]. 1. J. Tatchen, E. Pollak, , J. Chem. Phys. 128 (2008) 164303 2. Q. Peng, Y. Niu, C. Deng, Z. Shuai, Chem. Phys. 370 (2010), 215-222 3. R. Borrelli, A. Capobianco, A. Peluso, J. Phys. Chem. A 116 (2012) 9934-9940. 4. A. Baiardi, J. Bloino, V. Barone, J. Chem. Theory Comput. 9 (2013), 4097-4115. 5. F. Avila, J. Cerezo, J. Soto, R. Improta, F. Santoro, Comp. Chem. Theor. 2014 6. J. Huh, R. Berger, J. Phys: Conf. Ser. 380 (2012) 012019. 7. Y. Jiang, Q. Peng, X. Gao, Z. Shuai, Y. Niuc, S. H. Lin, J. Mat. Chem. 22 (2012), 4491 8. L. Cederbaum, E. Gindensperger, I. Burghardt, Phys. Rev. Lett. 94 (2005) 113003. 9. E. Gindensperger, L.S. Cederbaum J. Chem.Phys. 127 (2007) 124107. 10. D. Picconi, A. Lami, F. Santoro, J. Chem. Phys. 136 (2012) 244104. 11. D. Picconi, F. Avila, R. Improta, A. Lami, F. Santoro, Faraday Discuss., 2013, 163, 223 12. D. Padula, D. Picconi, A. Lami, G: Pescitelli, F. Santoro, J. Phys. Chem A 117 (2013) 3355-3368
Time dependent approaches for vibronic spectra and internal conversion rates in large systems
Fabrizio Santoro
2014
Abstract
TIME DEPENDENT APPROACHES FOR VIBRONIC SPECTRA AND INTERNAL CONVERSION RATES IN LARGE SYSTEMS Fabrizio Santoro Italian National Research Council, ICCOM-CNR, Area della Ricerca del CNR di Pisa, fabrizio.santoro@iccom.cnr.it. Thanks to the recent developments in electronic structure methods (mostly TD-DFT) and to the ever growing computational power the characterization of equilibrium geometries and Hessians of (mono-) excited electronic states of sizable molecules (dozens of heavy atoms) is nowadays straightforward in many cases. This has called for the development of automatic and user friendly methods for the computation of the line shapes of electronic spectra, able to extend the popular linear vibronic coupling model (LVC) to account for quadratic couplings (quadratic vibronic coupling, QVC). For harmonic systems with negligible nonadiabatic couplings path integral techniques [1-6] allow to derive an analytical expression of the finite-temperature time-correlation function whose Fourier transform gives the electronic spectrum. This quantum dynamical approach is very effective and delivers fully-converged spectra at almost no computational cost (few minutes of calculations), accounting for temperature, Duschinsky [1] and Herzberg-Teller effects [2-6]. The same kind of techniques permit to straightforwardly compute non-radiative rate constants driven by nonadiabatic couplings within Fermi Golden Rule [7], accounting for the effect of the bath of the vibronic states due to the whole set of molecular vibrations. We will show some applications made in our group. For systems where nonadiabatic couplings cannot be treated in a perturbative way, hierarchical representations of the Hamiltonian offer an effective route to reduce the dimensionality of the system and the computational cost of the quantum-dynamical simulations. Based on the original idea presented in refs [8-9] for LVC Hamiltonians, we proposed a method to build up the hierarchy of effective modes in QVC models [10-11]. This approach can be applied to the simulation of several electronic spectra. We show that in circular dichroism of exciton coupled dimers it is able to reproduce the characteristic alternation of positive and negative vibronic bands and it provides a robust simplified model to interpret the spectra in terms of the symmetry properties of pseudo-eigenfunctions of the effective modes [12]. 1. J. Tatchen, E. Pollak, , J. Chem. Phys. 128 (2008) 164303 2. Q. Peng, Y. Niu, C. Deng, Z. Shuai, Chem. Phys. 370 (2010), 215-222 3. R. Borrelli, A. Capobianco, A. Peluso, J. Phys. Chem. A 116 (2012) 9934-9940. 4. A. Baiardi, J. Bloino, V. Barone, J. Chem. Theory Comput. 9 (2013), 4097-4115. 5. F. Avila, J. Cerezo, J. Soto, R. Improta, F. Santoro, Comp. Chem. Theor. 2014 6. J. Huh, R. Berger, J. Phys: Conf. Ser. 380 (2012) 012019. 7. Y. Jiang, Q. Peng, X. Gao, Z. Shuai, Y. Niuc, S. H. Lin, J. Mat. Chem. 22 (2012), 4491 8. L. Cederbaum, E. Gindensperger, I. Burghardt, Phys. Rev. Lett. 94 (2005) 113003. 9. E. Gindensperger, L.S. Cederbaum J. Chem.Phys. 127 (2007) 124107. 10. D. Picconi, A. Lami, F. Santoro, J. Chem. Phys. 136 (2012) 244104. 11. D. Picconi, F. Avila, R. Improta, A. Lami, F. Santoro, Faraday Discuss., 2013, 163, 223 12. D. Padula, D. Picconi, A. Lami, G: Pescitelli, F. Santoro, J. Phys. Chem A 117 (2013) 3355-3368I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
