4,692 research outputs found
Poster P15: Excited states of molecular solutes with Quantum Monte Carlo: vertical transition and geometry optimization
No full textRecently, we have developed a novel Polarizable Continuum Model (PCM), which includes both surface and volume polarization of the dielectric medium (pure SVPE scheme), designed for the Quantum Monte Carlo (QMC) treatment of the solute. In particular, the treatment of volume polarization, due to quantum mechanical penetration of the solute charge density in the solvent domain, is based on quantum Monte Carlo techniques. The method allows to accurately solve Poisson's equation of the solvation model coupled with the Schrödinger equation for the solute [1,2,3]. The present model has been now extended to treat the effects of solvation in solute vertical electronic transitions and to the search of the solute equilibrium geometry in the excited states. For the first case, here we show the results of our study
performed on fast n → pi* and pi → pi* vertical transitions of s-trans- acrolein in water [4]. To perform calculations in a non-equilibrium solvation regime for the solute excited state, we have added a correction to the global dielectric polarization charge density, obtained self consistently with the solute ground-state wave function by assuming a linear-response scheme. The calculated solvatochromic shifts are properly described. For the second case, we start from recent
advances made to carry out the ground- and excited-state geometry optimization within QMC [5]. For the present purpose, we have extended the calculation of the forces to include solvent e_ects through our QMC implementation of PCM [6]. We show results, performed at the variational Monte Carlo level, on the excited-state geometry optimization of some small organic molecules in water solution and we make a comparison with the more widely used TDDFT and CASPT2 methods.
[1] C. Amovilli, C. Filippi, F. M. Floris, J. Phys. Chem. B (2006) 110 26225.
[2] C. Amovilli, C. Filippi, F. M. Floris, J. Chem. Phys. (2008) 129 244106.
[3] F. M. Floris, C. Filippi, C. Amovilli, J. Chem. Phys. (2012) 137 075102.
[4] F. M. Floris, C. Filippi, C. Amovilli, J. Chem. Phys. (2014) 140 034109.
[5] R. Guareschi, C. Filippi, J. Chem. Theor. Comput. (2013) 9 5513.
[6] R. Guareschi, F. M. Floris, C. Amovilli, C. Filippi, in preparation (2014)
Poster 0157: A novel continuum model for the calculation of solute-solvent dispersion contribution to the electronic excitation energy in solution.
No full textIn a recent work [1], we have presented a method to estimate the dispersion interaction energy between two molecules based on the measure of the electronic field fluctuations by means of quantum Monte Carlo (QMC) methodologies. The approach has been extended to the calculation of the dispersion contribution to the free energy of solvation within a continuum model framework. An explicit expression has been given and test calculations have been performed on atomic solutes in water as solvent. Here, we show for the first time, the generalization of the method to non-spherical solutes in ground an low lying excited states and in various solvents. The method involves the accurate calculation of the electronic wave function of the solute in ground and excited states while the solvent is treated as a continuum and is characterized by the refractive index and the ionization potential. We present results for different cavities. In all our calculations, we observe a red shift due to this contribution in the vertical electronic excitation energy of the solute.
[1] C. Amovilli and F. M. Floris, J. Phys. Chem. A 119: 5327 (2015
Prims (Floris). Antwerpen onder Lodewijk XV (1746-1748). Een bezettingsgeschiedenis
No full textSmekens F. Prims (Floris). Antwerpen onder Lodewijk XV (1746-1748). Een bezettingsgeschiedenis. In: Revue belge de philologie et d'histoire, tome 26, fasc. 1-2, 1948. pp. 238-246
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