text: (lead(II) dicarbonate) can be formed at 30 GPa and 2000K from PbCO and CO. It forms white monoclinic crystals, with space group P2/c and four formula units per unit cell. At 30 GPa the unit cell has a=4.771 b=8.079 c=7.070 Å and β=91.32°. The unit cell volume is 272.4 Å and density 7.59.
   (strontium dicarbonate) is very similar to the lead compound, and also has monoclinic structure with space group P2/c and four formula units per unit cell. At 30 GPa the unit cell has a=4.736 b=8.175 c=7.140 Å and β=91.34°. The unit cell volume is 276.3 Å and density 4.61. The double Sr=O bonds have lengths of 1.22, 1.24, and 1.25 Å. The single Sr-O bonds have lengths of 1.36 and 1.41 Å. The angles subtended at the carbon atoms are slightly less than 120°, and the angle at the C-O-C is larger.