Isostructural Tin and Germanium Carbonates (Sn[CO ₃ ] ₂ and Ge[CO ₃ ] ₂ )

High Resolution Image Download MS PowerPoint Slide Tin and germanium carbonates, Sn[CO 3 ] 2 and Ge[CO 3 ] 2, were synthesized by the reaction of SnO 2 or GeO 2 with CO 2 at high pressures and high temperatures in a laser-heated diamond anvil cell. Their structures were solved by in situ single-crystal X-ray diffraction at high pressures. Sn[CO 3 ] 2 formed at ∼30 GPa, while Ge[CO 3 ] 2 formed at around 44 GPa. Both carbonates are isostructural and crystallize in the trigonal space group P 3. The distinguishing feature of the Sn[CO 3 ] 2 or Ge[CO 3 ] 2 structures is the presence of isolated [CO 3 ] 2– groups, which are arranged in layers. Both structures contain octahedrally coordinated tetravalent Sn 4+ and Ge 4+ cations in two positions with partial site occupation. Bulk moduli of both carbonates are K 0 ≈ 44–48 GPa. Full geometry optimizations based on DFT calculations reproduced the crystal structures. The DFT models were used to complement the experimental compression data and for the assignment of Raman modes. Both Sn and Ge carbonates can be recovered under ambient conditions after pressure release.