Knowledge Bank

The Raman spectra and near-normal incidence infrared reflectivity spectra of single crystal aragonite, $CaCO3$ (space group $D2h16=Pnma$) are presented and symmetry-based vibrational assignments are given. The site group splittings and factor group splitting are calculated and compared with the pattern found in isostructural $KNO3$. The molecular dipole moment derivatives for the $\nu 3$ intramolecular motion of the $CO3=$ ion in $CaCO3$ (aragonite) are compared with the analogous quantity in $CaCO3$ (calcite).