Lattice dynamics of molecular calcite crystals.

Abstract

The lattice dynamics of molecular crystals (${\mathrm{CaCO}}_{3}$, ${\mathrm{MgCO}}_{3}$, and ${\mathrm{ZnCO}}_{3}$) has been investigated for the first time by means of the rigid-molecular-ion model developed by employing the external mode formalism and the interaction potential operative between nonbonded atoms. The phonon dispersion curves computed from this model are, generally, in good agreement with their available experimental data measured with the technique of inelastic neutron scattering. The values of the eigenvectors are also reported. The calculated values of the cohesive energy for ${\mathrm{CaCO}}_{3}$, ${\mathrm{MgCO}}_{3}$, and ${\mathrm{ZnCO}}_{3}$ show good agreement with the thermochemical data. The scope of further extension of the present model has also been discussed.