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### Résumé

A multiscale approach combining quantum mechanics (QM) and molecular mechanics methods has been employed to investigate the effects of solute-solute 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 Lennard-Jones potentials and Coulomb terms. Then, a reduced number of statistically-uncorrelated configurations are sampled and submitted to time-dependent Hartree-Fock calculations of the first hyperpolarizability. When only one molecule is described quantum-mechanically 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 solute-solute 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) centro-symmetric 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 |
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Numéro d'article | 234104 |

journal | The journal of chemical physics |

Volume | 141 |

Numéro de publication | 23 |

Les DOIs | |

Etat de la publication | Publié - 2014 |

## Empreinte digitale Examiner les sujets de recherche de « QM/MM investigation of the concentration effects on the second-order nonlinear optical responses of solutions ». Ensemble, ils forment une empreinte digitale unique.

## Projets

## PAI n°P7/05 - FS2: Systèmes supramoléculaires fonctionnels (PAI P7/05)

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

Projet: Recherche

## TINTIN - ARC 09/14-23: Molecular TINkertoys for OpToelectronics and SpINtronics - TINTIN

BONIFAZI, D., CHAMPAGNE, B., FORENSI, S., SEGERIE, A. & Melinte, S.

1/09/09 → 31/08/14

Projet: Recherche

## Équipement

## Plateforme Technologique Calcul Intensif

Benoît Champagne (!!Manager)

Plateforme technologique Calcul intensifEquipement/installations: Plateforme technolgique

## Contient cette citation

*The journal of chemical physics*,

*141*(23), [234104]. https://doi.org/10.1063/1.4903545