The vibrational spectrum of calcite (CaCO3): an ab initio quantum-mechanical calculation

The vibrational spectrum of calcite (CaCO3)is evaluated at an ab initio periodic quantum-mechanical level by using the CRYSTAL package. A localized basis set of Gaussian-type functions and the B3LYP hybrid Hamiltonian are adopted. The dynamical matrix is obtained by differentiating numerically the analytical first derivatives of the energy. The accuracy with respect to all computational parameters is documented. The calculated frequencies are compared with available IR and RAMAN data (16 and 5 peaks, respectively), the mean absolute error being less than 12 cm-1 (frequencies range from 100 to 1600 cm-1). Overall, the agreement with experiment is very satisfactory, and shows that simulation can produce at a relatively low cost the full spectra of crystalline compounds of mineralogical interest.