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Résumé
A multiscale approach combining quantum mechanics (QM) and molecular mechanics methods has been employed to investigate the effects of solutesolute interactions and therefore of concentration on the first hyperpolarizability of solutions of nitrobenzene in benzene. First, spatial distributions of solute and solvent molecules are generated using Monte Carlo simulations where the intermolecular interactions are described using the LennardJones potentials and Coulomb terms. Then, a reduced number of statisticallyuncorrelated configurations are sampled and submitted to timedependent HartreeFock calculations of the first hyperpolarizability. When only one molecule is described quantummechanically and is embedded in the electrostatic polarization field of the solution described by point charges, β_{HRS} and β_{//} as well as the depolarization ratio increase in parallel with the concentration in nitrobenzene. This effect is attributed to the increase of the polarization field associated with the presence of polar nitrobenzene molecules in the surrounding. Then, the first solvation shell is considered explicitly in the QM calculation to address solutesolute interactions effects. When the number of nitrobenzenes in the first solvation shell increases, β_{HRS} and β_{//} normalized to the number of nitrobenzene molecules decrease and this decrease attains roughly 50% when there are 3 nitrobenzene molecules in the first solvation shell. These drastic reductions of the first hyperpolarizability result from (partial) centrosymmetric arrangements between the nitrobenzene molecules, as supported by the relationship between β and the angle between the nitrobenzene charge transfer axes. Moreover, these β decreases originate mostly from the reduction of the dipolar β component, whereas the octupolar one is rather constant as a function of the nitrobenzene concentration.
langue originale  Anglais 

Numéro d'article  234104 
journal  The journal of chemical physics 
Volume  141 
Numéro de publication  23 
Les DOIs  
Etat de la publication  Publié  2014 
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Examiner les sujets de recherche de « QM/MM investigation of the concentration effects on the secondorder nonlinear optical responses of solutions ». Ensemble, ils forment une empreinte digitale unique.Projets
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