Simulation of vibrational spectra of crystals by ab initio calculations: an invaluable aid in the assignment and interpretation of the Raman signals. The case of jadeite (NaAlSi2O6)

Raman shifts of crystalline materials can reliably be evaluated at the ab initio level, provided that suitable Hamiltonians, like the hybrid Hartree–Fock/density functional theory ones, are employed in the calculation. The Raman shifts of jadeite (NaAlSi2O6) were obtained by using the WC1LYP hybrid Hamiltonian, and the results are compared with those available for experimental determinations. The average discrepancy between the experimental and calculated data is less than 4 cm–1, with positive and negative maximum discrepancies of 5.5 and 10.5 cm–1, respectively. Such results are useful (i) for the correct assignment of the observed Raman signals to fundamental vibrational modes; (ii) for the identification of modes too weak to be detected experimentally, and (iii) for the deconvolution of bands resulting from the overlap of several modes in the experimental spectra. Moreover, the attribution of each observed signal to a particular motion of the atoms in the structure has been performed and discussed.