Refractive index and third‐order nonlinear susceptibility of C₆₀ in the condensed phase calculated with the discrete solvent reaction field model

Abstract

ABSTRACT:We have calculated the frequency-dependent refractive index and the third-order nonlinear susceptibility for C 60 in the condensed phase, which is related to third-harmonic generation (THG) and degenerate four-wave mixing (DFWM) experiments. This was done using the recently developed discrete solvent reaction field (DRF) model, which combines a time-dependent density functional theory (TD-DFT) description of the central C 60 molecule with a classical polarizable MM model for the rest of the fullerene cluster. Using this model, effective microscopic properties can be calculated that, combined with calculated local field factors, give macroscopic susceptibilities. The largest calculation was for a cluster of 63 C 60 molecules in which the central molecule was treated with TD-DFT. For this molecule, the effective polarizability was increased with about 15% and the effective second hyperpolarizability with about 60% compared with the gas phase. The calculated refractive index was found to be in good agreement with experiments and other theoretical results. The agreement with THG experiments was within a factor of two, whereas for DFWM the agreement was less good due to the neglect of vibrational contributions in the calculations. It was found that it is more important to account for the dispersion in the third-order susceptibilities than in the corresponding second hyperpolarizability.

Attosecond chronoscopy of photoemission

“…The field distribution calculated from a simple hollow-sphere model for C 60 with the same polarizability ( ≃ 560 a.u.) as experimentally measured for C 60 (Jensen and Van Duijnen, 2005) agrees quite well with a time-dependent density functional theory (TDDFT) calculation on the adiabatic local density approximation (ALDA) level (Yabana and Bertsch, 1993;Wachter et al, 2014).…”

Self-assembled conjugated polymer spheres as fluorescent microresonators

“…Because the estimated exciton diffusion length is in the range of 5–20 nm1, the PL generated at the inner surface of the spheres accompanies the WGM peaks, even though the emission generated at the polymer/C 60 interface would be largely quenched. Since the refractive index of C 60 is larger than η polymer and in the range of 2.0–2.432, the confinement might be better for the C 60 -coated polymer spheres.…”

Atomic radii in molecules for use in a polarizable force field

“…In these studies, Thole's model has been applied successfully to a wide range of systems and problems, applications that were fully or in part based on classical simulations. With the DRF approach, we showed that Thole's model can be used to mimic quantum chemical calculations71, 72 including many‐body interactions43, and we addressed solvent effects on spectra73–76, chemical reactions77–79, and (hyper)polarizabilities2, 74, 80–85. All these DRF studies were already based on “good” ab initio atomic charges34, 58 and polarizabilities49, 69 but not yet atomic radii (vide supra).…”