Stacking Structure of Vaterite Revealed by Atomic Imaging and Diffraction Analysis.
Chemistry
; : e202401557, 2024 Jun 13.
Article
em En
| MEDLINE
| ID: mdl-38868960
ABSTRACT
Anhydrous calcium carbonate crystals exist as three polymorphs calcite, aragonite, and vaterite. Although vaterite is a metastable phase rarely found in the geological environment, it is intriguing that various biominerals are composed of vaterite. The processes of stable vaterite formation in biological systems cannot be understood without elucidating the nature of vaterite. The crystal structure of vaterite has been discussed for nearly a century but is still an open question. Here we propose the actual structure of vaterite by combining atomic imaging and diffraction analysis with simulations of disordered stacking sequences. Vaterite basically appears as layers of hexagonal calcium planes and carbonate (CO3 2-)-containing sheets stacked with +60°, -60°, or 180° rotations from the underlying layer. However, equivalent carbonate positions in alternating layers are forbidden, and four-layer stacking in which the fourth layer rotates 180° relative to the first layer are predominant, forming an orthogonal reciprocal lattice in diffraction patterns. These stacking characteristics replicate the intensity distribution in the electron and X-ray diffraction patterns. This study has almost completely elucidated the crystal structure and stacking sequence of vaterite. Our findings provide insights into the thermodynamic stability of vaterite, which facilitates comprehension of the biomineralization processes and growth dynamics of calcium carbonate.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Chemistry
Assunto da revista:
QUIMICA
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Japão