eprintid: 1561880 rev_number: 29 eprint_status: archive userid: 608 dir: disk0/01/56/18/80 datestamp: 2017-07-09 00:37:31 lastmod: 2021-10-05 00:21:50 status_changed: 2017-11-20 15:10:42 type: article metadata_visibility: show creators_name: Gonzalez-Lopez, J creators_name: Cockcroft, JK creators_name: Fernandez-Gonzalez, A creators_name: Jimenez, A creators_name: Grau-Crespo, R title: Crystal structure of cobalt hydroxide carbonate Co2CO3(OH)(2): density functional theory and X-ray diffraction investigation ispublished: pub divisions: UCL divisions: B04 divisions: C06 divisions: F56 keywords: Science & Technology, Physical Sciences, Chemistry, Multidisciplinary, Crystallography, Chemistry, Co2CO3(OH)(2), density functional theory, powder X-ray diffraction, rosasite, malachite, TOTAL-ENERGY CALCULATIONS, AUGMENTED-WAVE METHOD, CALCIUM-CARBONATE, THERMAL-CONVERSION, BASIS-SET, ROSASITE, CO3O4, HYDROXYCARBONATE, GLAUKOSPHAERITE, POLYMORPHS note: The Creative Commons Attribution (CC-BY) Licence applies to all open-access articles published by the IUCr. Under this licence the authors retain the copyright of their article, but allow others to reuse and copy the article provided the original authors and source are cited. abstract: The cobalt carbonate hydroxide Co2CO3(OH)2 is a technologically important solid which is used as a precursor for the synthesis of cobalt oxides in a wide range of applications. It also has relevance as a potential immobilizer of the toxic element cobalt in the natural environment, but its detailed crystal structure is so far unknown. The structure of Co2CO3(OH)2 has 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 but symmetrically different crystal structures, based on those of the minerals malachite [Cu2CO3(OH)2] and rosasite [Cu1.5Zn0.5CO3(OH)2], as well as an orthorhombic phase that can be seen as a common parent structure for the two monoclinic phases, and a triclinic phase with the structure of the mineral kolwezite [Cu1.34Co0.66CO3(OH)2]. The DFT simulations predict that the rosasite-like and malachite-like phases are two different local minima of the potential energy landscape for Co2CO3(OH)2 and are practically degenerate in energy, while the orthorhombic and triclinic structures are unstable and experience barrierless transformations to the malachite phase upon relaxation. The best fit to the PXRD data is obtained using a rosasite model [monoclinic with space group P1121/n and cell parameters a = 3.1408 (4) Å, b = 12.2914 (17) Å, c = 9.3311 (16) Å and γ = 82.299 (16)°]. However, some features of the PXRD pattern are still not well accounted for by this refinement and the residual parameters are relatively poor. The relationship between the rosasite and malachite phases of Co2CO3(OH)2 is discussed and it is shown that they can be seen as polytypes. Based on the similar calculated stabilities of these two polytypes, it is speculated that some level of stacking disorder could account for the poor fit of the PXRD data. The possibility that Co2CO3(OH)2 could crystallize, under different growth conditions, as either rosasite or malachite, or even as a stacking-disordered phase intermediate between the two, requires further investigation. date: 2017-10-01 date_type: published publisher: INT UNION CRYSTALLOGRAPHY official_url: http://doi.org/10.1107/S2052520617007983 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green article_type_text: Article verified: verified_manual elements_id: 1297955 doi: 10.1107/S2052520617007983 lyricists_name: Cockcroft, Jeremy lyricists_id: CCOCK10 actors_name: Cockcroft, Jeremy actors_name: Laslett, David actors_id: CCOCK10 actors_id: DLASL34 actors_role: owner actors_role: impersonator full_text_status: public publication: Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials volume: B73 pagerange: 868-873 pages: 6 issn: 2052-5206 citation: Gonzalez-Lopez, J; Cockcroft, JK; Fernandez-Gonzalez, A; Jimenez, A; Grau-Crespo, R; (2017) Crystal structure of cobalt hydroxide carbonate Co2CO3(OH)(2): density functional theory and X-ray diffraction investigation. Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials , B73 pp. 868-873. 10.1107/S2052520617007983 <https://doi.org/10.1107/S2052520617007983>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/1561880/1/Cockfroft_wf5134.pdf