Molecular simulation of static hyper-Rayleigh scattering: A calculation of the depolarization ratio and the local fields for liquid nitrobenzene

Abstract

Papadopoulos, M. G. (1999). Molecular simulation of static hyper-Rayleigh scattering : a calculation of the depolarization ratio and the local fields for liquid nitrobenzene. Journal of Chemical Physics, 111(21), 9711-9719. DOI: 10.1063/1.480305 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Molecular dynamics ͑MD͒ simulation is used to assess the hyper-Rayleigh scattering ͑HRS͒ depolarization ratio of liquid nitrobenzene subject to vertically polarized light. In contrast to previous theoretical work, we have quantified both incoherent and coherent scattering arising from positional and orientational inhomogeneities in the molecular distribution. Although coherent scattering is shown to be much less important than in the case of Rayleigh scattering, it can not be neglected. Therefore, our analysis supports the current practice of working with dilute solutions ͑for which coherent contributions to HRS are truly negligible͒ to extract the first molecular hyperpolarizability from HRS measurements. In cases where experiments with pure liquids can not be circumvented, our analysis may be used to separate coherent and incoherent signals. Our work, which uses as input static ''gas-phase'' ͑hyper͒polarizabilities obtained from ab initio calculations, also provides information on the orientations and magnitudes of the local electric fields experienced by the individual molecules in the liquid. For nitrobenzene it is found that the local fields are largely determined by specific dipolar alignment between neighboring pairs of molecules, with consequences on the HRS signal.

Molecular Dynamics Study of 2-Nitrophenyl Octyl Ether and Nitrobenzene

“…Another feature that might be observed in the JAN model RDF is a peak at very short molecular separations (about 0.38 nm), which becomes a shoulder in the MB model and is almost indistinguishable in the OPLS model. This feature has been assigned by Janssen et al 13 to pairs of nitrobenzene molecules with antiparallel dipolar alignment, and such preferred alignment can also be noticed in Figure 3b.…”

“…The second model is due to Janssen et al (JAN) 13 and is also based on the work by Shlyapochnikov et al 19 Its charges were calculated from a Mulliken population analysis, and also rescaled to match the experimental dipole moment. The L-J parameters were taken from literature values for benzene and the nitro group, and were not further optimized.…”

“…11,12 In contrast, few theoretical studies have been devoted to probe such organic solvents. NB has been studied by molecular simulation in the context of light scattering, 13 and of liquid|liquid interfaces, [14][15][16] as well as for the optimization of force-field parameters. 17,18 Although some useful information can be extracted from those studies, none has presented a systematic and detailed analysis of the thermodynamic and dynamic properties of the bulk liquid.…”

Electrically controlled light scattering from thermoreversible liquid-crystal gels

“…3͑a͒ has vanished. The outer ring, which originates from electron density variations caused by a parallel local arrangement of neighboring LC molecules, 25 is still present. Note that the reflections of the ordered ͕C 2 ͖ phase have remained unchanged when compared to Fig.…”

The Contribution of Molecular Modeling to the Knowledge of Pesticides

“…As for photocatalysis, the OH radical attack appeared to be non-selective and all three possible isomers showed comparable stabilities. Although nitro compounds are of general and biological significance, only a limited number of studies have focused on developing force field (FF) parameters for use in molecular simulations (Michael & Benjamin, 1998;Janssen et al, 1999;Price et al, 2001;2005;Jorge et al, 2006). Price et al (2001) developed nitro-parameters for the OPLS-AA FF (Jorgensen et al, 1988; that resulted in good agreement with experimental gas-phase and liquid properties, e.g., density, heats of vaporization, and free energies of salvation, from molecular simulations.…”