Ab InitioStudy of the Vibrational Spectrum and Related Properties of Crystalline Compounds; the Case of CaCO₃Calcite

Abstract

Vibrations / Calcite / IR Intensities / Ab Initio SimulationThe static and high frequency dielectric tensors, Born effective charges, vibrational spectrum at the Γ point, TO-LO splitting and IR intensities of calcite CaCO 3 have been calculated with the periodic ab initio CRYSTAL program, with five different basis sets of increasing size and four different Hamiltonians (HF, LDA, PBE, B3LYP). B3LYP is shown to perform better than the other options, in particular of LDA and PBE that are often used for the calculation of the vibrational spectrum of crystalline solids. When comparing B3LYP and experimental frequencies, the mean absolute difference is as small as 8.5 cm −1 ; this number reduces to 4.8 cm −1 if the two lowest experimental frequencies, that we suspect to be affected by a relatively large error, are excluded from statistics. Static and high frequency dielectric tensors, as well as IR intensities computed with the same hybrid scheme (B3LYP) compare quite favourably with experiment. The full set of modes is characterized by various tools including isotopic substitution, "freezing" one of the two subunits (Ca 2+ or CO 3 2− ) and graphical representations. A general tool has been implemented, that permits the automatic generation of the animation of the full set of modes starting from the CRYSTAL output (available at www.crystal.unito.it/vibs/ calcite).

Ab initioand photoemission study of correlation effects in SrRuO3thin films

“…57 For the O atom, the all-electron basis set originally used to study calcium carbonate was taken from Ref. 58.…”

The magnetic and electronic structure of vanadyl pyrophosphate from density functional theory

“…Each atom is described by an all-electron, Gaussian-type basis set: 86-411d31G for V, 24,25 85-21d1G for P, 26 and 8-411d11G for O, 27 all of which have double zeta plus polarization quality.…”

The crystalline structure of SrRuO3: Application of hybrid scheme to the density functionals revised for solids

“…The small-core Hay-Wadt pseudopotentials [11] were utilized to describe the inner-shell electrons (1s (4s 2 4p 6 5s 2 ) was taken from the SrTiO 3 study [12], while the valence functions for Ru (4s were adopted from our previous work on non-stoichiometric SrRuO 3 [13]. Concerning the oxygen atom, all-electron basis set was applied from the calcium carbonate study [14].…”