|Author||Zlotoyabko, E. ♦ Caspi, E. N. ♦ Fieramosca, J. S. ♦ Von Dreele, R. B. ♦ Marin, F. ♦ Mor, G. ♦ Politi, Y. ♦ Weiner, S.|
|Sponsorship||USDOE Office of Science (SC)|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Subject Keyword||INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY ♦ BOND LENGTHS ♦ CALCITE ♦ CARBONATES ♦ COMPARATIVE EVALUATIONS ♦ DATA ANALYSIS ♦ ELONGATION ♦ FREQUENCY ANALYSIS ♦ LINE BROADENING ♦ LINE WIDTHS ♦ MAGNESIUM ♦ NEUTRON DIFFRACTION ♦ POWDERS|
|Abstract||We used high-resolution neutron powder diffraction to accurately measure the atomic positions and bond lengths in biogenic and geological calcite. A special procedure for data analysis was developed in order to take into account the considerable amounts of magnesium present in all the investigated samples. As a result, in biogenic calcite we found some atomic bonds to have significantly different lengths as compared to those in geological calcite, after the contribution of magnesium is accounted for. The maximum effect (elongation up to 0.7%) was found for the C-O bonds. We also analyzed changes in frequencies and spectral widths of normal vibrations of carbonate groups in biogenic calcite (as compared to geological calcite) measured by Raman and Fourier transform IR techniques. Surprisingly, the frequency shifts after subtracting the magnesium contribution are close to zero. At the same time, substantial spectral broadening (up to 1.2%) in biogenic calcite as compared to geological samples was detected. Possible explanations for the experimental findings are discussed.|
|Learning Resource Type||Article|
|Publisher Place||United States|
|Journal||Crystal Growth and Design|
|Technical Publication No.||ANL/XSD/JA-65103|
|Organization||Argonne National Lab. (ANL), Argonne, IL (United States)|
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