Predicting Raman Spectra Using Density Functional Theory

Abstract

Accurately computing molecular Raman spectra would enable rapid development of inexpensive and extensive Raman libraries. This is especially beneficial for chemicals that are regulated, toxic, or otherwise difficult to handle. Numerous quantum mechanical methods have been developed that enable computation of Raman spectra. Here, we study the B3LYP exchange correlation functional with various combinations of basis sets, polarization functions, and diffuse functions to determine which combination best computes the Raman spectra for explosive and nonexplosive molecules. In comparing spectra, three metrics were utilized: the root mean square error, the earth mover's distance, and the weighted cross-correlation average. The earth mover's distance and weighted cross-correlation metrics are shown to have significantly greater power at detecting spectral similarities and differences than the root mean square error. Across all methods and molecules examined, B3LYP/6-311++G(d,p) was found to provide the best match between measured and computed Raman spectra. Spectra generated at the B3LYP/6-311++G(d,p) level were found to be accurate enough to correctly identify each molecule out of a set of measured molecular spectra.

Experimental and ab initio DFT calculated Raman spectrum of Sudan I, a red dye

“…The calculations suggest that the nature of the bands at around 1600-1500 cm −1 are rather complex but have been oversimplified in previous studies. In accordance with these previous studies, we also assign many of these vibrawileyonlinelibrary.com/journal/jrs [19] c Stretch, stretching; bend, bending; ip, in-plane; oop, out-of-plane; asym, asymmetric; sym, symmetric; scis, scissoring; triang, triangular; ph: phenyl ring; naph, naphthyl ring. d These bands were significantly enhanced when using the green laser.…”

“…Below about 900 cm −1 , many out-of-plane bending modes were dominant. Low-intensity bands at 721, 616, 463 and 218 cm −1 were selectively enhanced by the RR effect, when using wileyonlinelibrary.com/journal/jrs [19] .…”

“…The scaling factor was chosen to be 0.976 on the basis of results from Ref. [19], where a number of calculated and experimental spectra of C-, H-, N-and O-containing compounds were compared using several basis sets to find the best scaling factor.…”

Investigation ofL(+)-Ascorbic acid with Raman spectroscopy in visible and UV light

“…It appeared that the Gaussian 03W program (60) could give reasonably reliable results at the DFT/B3LYP/6-311++G(d,p) level (61).…”

Raman Characterization of Phenyl-Derivatives: From Primary Amine to Diazonium Salts

“…The vibrational wavenumbers and normal modes were calculated within their harmonic approximation. A scaling factor of 0.976 was chosen on the basis of previously published work [28].…”