Crystal structure of cobalt hydroxide carbonate Co2CO3(OH)2: density functional theory and X-ray diffraction investigation.

摘要: The cobalt carbonate hydroxide Co2CO3(OH)2 is a technologically important solid which used as precursor for the synthesis of oxides in wide range applications. It also has relevance potential immobilizer toxic element natural environment, but its detailed crystal structure so far unknown. now been investigated using density functional theory (DFT) simulations and powder X-ray diffraction (PXRD) measurements on samples synthesized via deposition from aqueous solution. Two possible monoclinic phases are considered, with closely related symmetrically different structures, based those minerals malachite [Cu2CO3(OH)2] rosasite [Cu1.5Zn0.5CO3(OH)2], well an orthorhombic phase that can be seen common parent two phases, triclinic mineral kolwezite [Cu1.34Co0.66CO3(OH)2]. DFT predict rosasite-like malachite-like local minima energy landscape practically degenerate energy, while structures unstable experience barrierless transformations to upon relaxation. best fit PXRD data obtained model [monoclinic space group P1121/n cell parameters = 3.1408 (4) A, b 12.2914 (17) A, c 9.3311 (16) A γ 82.299 (16)°]. However, some features pattern still not accounted by this refinement residual relatively poor. relationship between discussed it shown they polytypes. Based similar calculated stabilities these polytypes, speculated level stacking disorder could account poor data. possibility crystallize, under growth conditions, either or malachite, even stacking-disordered intermediate two, requires further investigation.