Crystal Structure of Ca₂Na₂(CO₃)₃ (Shortite)

Area of Science:

• Inorganic Chemistry
• Crystallography
• Materials Science

Background:

• Understanding the precise atomic arrangement of inorganic compounds is crucial for predicting their properties.
• Previous structural data for Ca₂Na₂(CO₃)₃ may require refinement or correction.
• Layered structures in carbonates can influence bulk material characteristics.

Purpose of the Study:

• To redetermine, correct, and refine the crystal structure of Ca₂Na₂(CO₃)₃.
• To elucidate the coordination environment of calcium and sodium ions.
• To analyze the coordination preferences of carbonate groups within the crystal lattice.

Main Methods:

• Single-crystal X-ray diffraction was employed.
• The crystal structure was refined using 684 observed reflections.
• Corrections for absorption and isotropic extinction were applied.

Main Results:

• The compound crystallizes in the orthorhombic space group Amm2 with refined unit cell parameters.
• A layered structure was identified, with Ca₂NaCO₃ layers interleaved with Na(CO₃)₂ layers.
• Detailed coordination numbers and distances for Ca and Na ions with oxygen atoms and carbonate groups were established.

Conclusions:

• The refined structure provides accurate crystallographic data for Ca₂Na₂(CO₃)₃.
• The coordination analysis highlights specific interactions between cations and carbonate anions.
• Carbonate groups exhibit a preference for edge-sharing with calcium ions, influencing the overall structural framework.