Polymer Optical Constants from Long-Range Corrected DFT Calculations

Abstract

A methodology to calculate refractive indices of plastics based on the Lorentz-Lorenz equation has been proposed. The polarizability of the nonconjugated polymer repeat units is predicted using the long-range corrected functionals. The end effect corrections in repeat unit models are essential to achieve accuracy similar to that observed for molecular liquids (ca. 1% in mean absolute deviation). The functionals with 100% Hartree-Fock (HF) exchange in the long-range limit perform best for aromatic and other hydrogen-deficient compounds; the Coulomb-attenuated hybrid exchange-correlation functional (CAM-B3LYP) performs very well for hydrogen-rich (usually, fully saturated) compounds. Exceptionally good agreement is observed for the sets of wavelength-dependent refractive index data for polystyrene, poly(methyl methacrylate), and for poly(perfluoro-4-vinyloxy-1-butene) (CYTOP), for which the root-mean-square deviations are 0.004, 0.002, and 0.004, respectively.

Refractive indices of organo‐metallic and ‐metalloid compounds: A long‐range corrected DFT study

“…Conversely, when a contribution of the GGA exchange‐correlation in the functional increases, the computed polarizabilities become higher than the experimental values. This tendency is consistent with our previous results for the refractive indices of small organic molecules and polymers …”

“…Among the functionals studied here, LC‐BLYP is again one of the best functional to yield the lowest MSRE (−0.4%), MARE (0.7%), and RMSD (0.013; see Table ). Similar observations have been made earlier for small organic molecules and polymers . Although the lowest MAXRE is seen for LC‐PBE (1.9%), MAXRE for LC‐BLYP (2.0%) is almost the same.…”

“…Their microscopic theory strongly suggests that the Lorentz–Lorenz equation is a very good approximation even for molecular systems. Indeed, the Lorentz–Lorenz equation yields predictions often in excellent agreement with experiments, when both the polarizability and the density are estimated accurately …”

“…Thus, we applied these methods to evaluate the refractive indices of organometallic and organometalloid liquids. Although the polarizability of an isolated molecule may change when it is brought into a liquid phase, the effect seems to be small in general . Therefore, we adopted the simplest model for evaluating polarizability of the liquids – an isolated molecule model.…”

“…Since the LC‐DFT describes better excitation properties, it may also represent better polarizability. Indeed, we have numerically proven that both the LC‐BLYP and CAM‐B3LYP allow us to evaluate the refractive index of small organic molecules and polymers accurately . Thus, it is interesting to investigate whether the LC‐DFT evaluates refractive indices of metal‐ and metalloid‐containing compounds with a similar accuracy.…”