The vibrational spectrum of CaCO3 aragonite: A combined experimental and quantum-mechanical investigation

Abstract

The vibrational properties of CaCO 3 aragonite have been investigated both theoretically, by using a quantum mechanical approach (all electron Gaussian type basis set and B3LYP HF-DFT hybrid functional, as implemented in the CRYSTAL code) and experimentally, by collecting polarized infrared (IR) reflectance and Raman spectra. The combined use of theory and experiment permits on the one hand to analyze the many subtle features of the measured spectra, on the other hand to evidentiate limits and deficiencies of both approaches. The full set of TO and LO IR active modes, their intensities, the dielectric tensor (in its static and high frequency components), and the optical indices have been determined, as well as the Raman frequencies. Tools such as isotopic substitution and graphical animation of the modes are available, that complement the analysis of the spectrum.

Phase transitions in the system CaCO3 at high P and T determined by in situ vibrational spectroscopy in diamond anvil cells and first-principles simulations

“…The assignment of spectral features, especially of new high-pressure phases is not straightforward, but can be supported by electronic structure calculations in the framework of density-functional perturbation theory (DFPT). Theoretical Raman and IR spectra of carbonates at ambient pressure and zero temperature have been reported, e.g., by Valenzano et al (2007), Carteret et al (2013) and on www.wurm.info (Caracas and Bobocioiu, 2011).…”

Infrared and Raman spectroscopic features of the self-interstitial defect in diamond from exact-exchange hybrid DFT calculations

“…[26][27][28][29][30][31][32][33] In the present study, ab initio calculations are performed to investigate the electronic and spectroscopic properties of the self-interstitial 100 defect in diamond, by use of a periodic super-cell approach and of the hybrid B3LYP functional, which contains 20% of non-local exact exchange (an essential prerequisite to the correct description of the electronic spin localization at the defect), [34][35][36][37][38][39] as implemented in the CRYSTAL14 program. 33 The effects of different defect concentrations and spin states are explicitly explored.…”

The Raman spectrum of CaCO3 polymorphs calcite and aragonite: A combined experimental and computational study

“…Previous simulations on the vibrational properties of carbonates have mainly focused on methodological aspects, 17 on the effect of cation substitutions on the infrared spectra, 18 and on the role of the vibrational contributions to the relative stability of polymorphs. 19 Some of the present authors have recently presented an accurate study on the infrared and Raman properties of aragonite, 10 and a similar one had been devoted 8 years ago to calcite 20 ; in both cases Raman intensities were not available.…”