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Keywords:

  • density functional theory;
  • hybrid functionals;
  • aluminosilicates;
  • vibrational spectrum;
  • local basis set

Abstract

The performance of eleven DFT functionals in describing the equilibrium structure and the vibrational spectra at the Γ point of pyrope (Mg3Al2Si3O12), forsterite (α-Mg2SiO4), α-quartz (α-SiO2) and corundum (α-Al2O3) is discussed. The four systems, for which accurate experimental data are available, are here used as a representative sample of the large aluminosilicates family. Calculations were performed with the periodic ab initio CRYSTAL code by using all-electron Gaussian-type basis sets. All the functionals here considered provide reasonable structural predictions, the hybrid PBE0 giving the least deviation from the experimental unit cell volumes (from −0.3% to +0.6%). At the other extreme, SVWN and SPWLSD (≃−3%) and PBE and PW91 (≃ +3%) provide the largest volume under- and over-estimation, respectively. Vibrational frequencies are more accurate when computed with hybrid functionals, with the best performance provided by B3LYP and WC1LYP (mean absolute differences with respect to experiments evaluated on a set of 134 vibrational frequencies, |equation image|t ≃ 5.5 cm−1). The three recently proposed GGA functionals, PBEsol, SOGGA-PBE and WC-PBE, provide a good description of the vibrational spectra, of the same quality as the one provided by PBE0 and B1WC (|equation image|t ≃ 10 cm−1), whereas poorer results are obtained with PBE (|equation image|t ≃ 17 cm−1). © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010